Mars Research Papers

Physics of the Earth and Planetary Interiors 117 Ž2000. 437–447 www.elsevier.comrlocaterpepi

The change of eruption styles of Martian volcanoes and estimates of the water content of the Martian mantle Tomonori Kusanagi ) , Takafumi Matsui Department of Earth and Planetary Physics, UniÕersity of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan Received 3 December 1998; accepted 10 May 1999

Abstract Estimated water contents in the Martian mantle range from 36 ppm to more than 1%. These values are based on the chemical analyses such as hydrous minerals in SNC meteorites and formation models of Mars. This study evaluates the water content of the Martian mantle using the change with time of volcanic eruption style on Mars as an observational constraint. Styles of volcanic activity depend on the volatile content of the magma and the atmospheric pressure. Because a low atmospheric pressure leads to a more explosive volcanic eruption, it has been believed that the volcanism on the current Martian environment would be very explosive. Our calculations, however, show that, under the current Martian atmospheric conditions, erupted magma cannot entrain the ambient air effectively, so the decrease in temperature of the magma during ascent is small. Consequently, the erupted magma may form a lava-like deposit when it falls back on the ground. This effusive-like style of eruption is a counterpart of clastogenic lava on Mars. On the other hand, numerical calculations under a thick CO 2 atmosphere, which may correspond to an ancient Martian atmosphere, reveal a rather explosive eruption style. Geological features of earlier stages of Martian history in the Noachian and Hesperian eras suggest that the volcanic eruptions on Mars were explosive then. Effusive eruptions, however, became dominant in more recent times. It has been widely accepted that Mars experienced a major climate change. In addition, the release factor of volatiles on Mars has been suggested to be as small as 0.017–0.112. This may imply that the volatile content has been almost constant throughout Martian history. Consequently, we assume that this change in eruption style was caused by the change in atmospheric pressure. For a given water content of magma, a major climatic change may lead to a transition in eruption style. If we know the atmospheric pressure at the time of this transition, we can calculate the possible range of the volatile content of the mantle using our numerical simulations. If the atmospheric pressure on Mars around late Hesperian era is about 1 bar, the estimated values for a typical Martian magma are 0.05–0.25 wt.%, which is within the range of the water content of typical terrestrial basaltic magmas. q 2000 Elsevier Science B.V. All rights reserved. Keywords: Eruption styles; Martian volcanoes; Martian mantle

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Corresponding author. e-mail: [email protected]

0031-9201r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 3 1 - 9 2 0 1 Ž 9 9 . 0 0 1 1 2 - 0

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T. Kusanagi, T. Matsuir Physics of the Earth and Planetary Interiors 117 (2000) 437–447

1. Introduction A number of observations from both the ground and space probes such as Vikings 1 and 2, the recent Mars Pathfinder, and Mars Global Surveyor have shown that there are various volcanic features on Mars. Some of these volcanoes are much larger than the terrestrial counterparts. Particularly, Olympus Mons, one of the largest volcanoes on Mars, has a height of ; 27 km and a diameter of ; 600 km. Most volcanic features on Mars seem to be the results of effusive volcanic activities involving lava flows. Several large volcanoes are similar to shield volcanoes on Earth and thought to be composed largely of low-viscosity basaltic lava Že.g., Cattermole, 1989; Mouginis-Mark and Wilson, 1992.. Several other volcanoes, however, show the signs of explosive eruptions Že.g., Mouginis-Mark et al., 1982, 1988; Greeley and Crown, 1990.. For example, a group of Martian volcanoes called ‘‘highland paterae’’ have highly eroded slopes suggesting that their main bodies may have been constructed of ash or pyroclastic deposits ŽGreeley and Spudis, 1978; Greeley and Crown, 1990; Crown and Greeley, 1993.. Based on the crater density on the flanks of Martian volcanoes, Plescia and Saunders Ž1979. argued that there were various styles of volcanic activities on the early stage of Martian volcanism but that only effusive volcanism survived until the later stages. Tanaka Ž1986. analyzed the stratigraphy of Mars in detail and concluded that Ži. the activities of highland paterae started in the late Noachian epoch, Žii. volcanism prevailed over all the volcanic regions on Mars during the Hesperian epoch, and Žiii. the active region was confined to a few locations such as the Tharsis region from the late Hesperian to the Amazonian epoch. A general trend found here is that older volcanoes such as highland paterae may have been formed by explosive activity, and more recent volcanoes are composed of lava flows due to effusive activity.

when the volume fraction of gases in the magma exceeds a critical value. The volume of the exsolved gases is controlled by the solubilities of the gases to the magma, which is a function of pressure. Consequently, the explosivity of the magma depends on the gas mass fraction of the magma, the solubility of each volatile, and the surface pressure of the planet. The solubility of water into basaltic magma, n d , is given as a function of pressure P in Pa, as follows ŽBurnham, 1975; Wilson and Head, 1981; Stolper and Holloway, 1988; Pan et al., 1991.: n d Ž P . s 6.8 = 10y8 P 0.7

Ž 1.

Fig. 1 shows the above relation. Under the surface pressure of Earth, at least ; 0.1 wt.% of water must be dissolved into the magma for an explosive eruption to be possible. On Mars, however, only about 7 ppm of water is enough to cause explosive volcanic activity because of the low surface pressure ŽWilson and Head, 1981.. This means that effusive eruptions are very hard to produce on Mars because the smallest estimate for the water content of Martian magma is 36 ppm ŽDreibus and Wanke, 1987.. The observed ¨ morphology of the Martian surface shows that effusive volcanism is rather dominant in more recent ages, which is not consistent with the consideration above. Wilson and Head Ž1994. suggested the possibility that Hawaiian-type eruptions should have existed on Mars. In such eruptions, optically dense fire fountains and ineffective entrainment of ambient air keep the inner parts of fountains hot. Consequently, landing magma clots coalesce to form rootless lavas or magma ponds, even if the magma experienced disruption. The observed large-scale volcanic features on Mars may have been formed through such eruptions. To evaluate this possibility and derive the conditions to result in such volcanic activity, we carried out numerical calculations of volcanic eruption processes under Martian conditions.

3. Model 2. The condition for an explosive eruption An explosive volcanic eruption occurs when magma disrupts. The disruption condition is reached

We adopted the model by Sugita and Matsui Ž1998. for Martian conditions. This model consists of two parts, magma rise through the conduit and ascent of an eruption cloud in the atmosphere. In

T. Kusanagi, T. Matsuir Physics of the Earth and Planetary Interiors 117 (2000) 437–447

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Fig. 1. Conditions for explosive and effusive eruptions. The explosivity of magma depends on the pressure at the planetary surface. Under the current Martian atmosphere, more than 7 ppm of H 2 O is needed for basaltic magma to erupt explosively. This value is smaller than the Ž1987.. least estimate for the H 2 O content of Martian mantle by Dreibus and Wanke ¨

both regions, one-dimensional homogeneous steady flow is assumed. Our model also considers the effect of gas bubbles on magma viscosity ŽJaupart, 1996.. 3.1. The conduit The generally accepted view of the volcanic eruption process is as follows. First, magma in the magma reservoir starts to rise because of buoyancy forces ŽWilson and Head, 1981.. Thus, as it approaches the surface, the pressure decreases and the volatiles dissolved in the magma exsolve as gas bubbles, so that the density of the magma decreases ŽWilson and Head, 1981.. As a result, the magma gains buoyancy. The ascent velocity of the magma mainly depends on both this buoyancy and the wall friction ŽMcGetchin and Ulrich, 1973.. This is not strictly true, as one may include some overpressure due to elastic effects Žfor example, around a storage region. and viscous stresses are dominant except at the very late stages of ascent when the magma is fragmented. However, since it its difficult to take into account the

effect of overpressure, we simply assume that the pressure in the conduit is in equilibrium with that of the surroundings. The effect of viscous stresses might be taken into account partly in our model because in the assumption of one-dimensional flow the viscous stress due to horizontal velocity gradient is implicitly included in wall friction. When the gas volume fraction reaches a critical value, bubbles in the magma come into contact with each other. Then the magma disrupts and the expansion of the gas phase causes an explosive and violent eruption. If magma disruption does not happen, the eruption is effusive and forms a lava deposit. The critical gas volume fraction for magma disruption is estimated to be around 70% based on the measurement of erupted materials on Earth ŽSparks, 1978.. Following Sugita and Matsui Ž1998., we use the equations by Wilson and Head Ž1981. to describe the behavior of magma in the conduit. The equations of mass and momentum conservation are numerically solved to obtain the vent diameter and the velocity of magma. Each equation is given as follows.

T. Kusanagi, T. Matsuir Physics of the Earth and Planetary Interiors 117 (2000) 437–447

440

Ža. Mass conservation F s p a 2r u s F0 s constant

Ž 2.

where a is the vent radius, r is the bulk density of magma, u is the vertical velocity, F is the mass flux and F0 is the mass flux at the depth where gas exsolution initiates Žhereafter, we call this the exsolution depth.. We assume no mass transfer between magma and conduit wall. We begin our numerical simulation by giving the velocity of magma at the exsolution depth, which is assumed to be the terminal velocity of bubble-free magma by Wilson and Head Ž1981.. Žb. Momentum conservation: u

du

fu 2

1 dP sy

y

r dz

dz

4a

yg

Ž 3.

where z is the depth from the planetary surface, f is the friction coefficient and g is the gravity acceleration. The friction coefficient f is given as a function of the Reynolds number Re by: fs

64 Re

q f0

Ž 4.

where f 0 is the constant of ; 0.01. The volcanic gas is assumed to be a perfect gas and the mixture density of gas and pyroclasts is given by: 1 s

r

1 y ne

s

q

ne Ru P

Ž 5.

where n e is the mass fraction of exsolved gas, s is the density of pyroclasts, R is the gas constant of the volcanic gas and u is the temperature of magma. The temperature of magma might be considered to decrease because of the thermal expansion of the gas phase and heat loss through the conduit wall. However, this is not the case. The heat loss through the conduit wall is negligible because the time scale of magma ascent is much smaller than that of the thermal conduction ŽWilson and Heslop, 1990.. The temperature change due to bubble expansion is also very small because the mass fraction of gas phase is much smaller than that of the pyroclasts and the surrounding magma acts as an effective heat buffer ŽSparks, 1978.. Consequently, the magma rise process may be assumed to be isothermal.

The motion of magma is controlled by many parameters, including magma viscosity, temperature, density, vent geometry, the depth of the magma reservoir, the volatile content and its solubility to magma. We use the values of basaltic magma as the magma viscosity, temperature and density and we consider water as the volatile. Vent geometry affects the motion of magma. Giberti and Wilson Ž1990. studied the influence of geometry on the ascent of magma in open fissures. However, we simply assumed that the conduit is a circular tube. The radius of the conduit is considered to change according to the pressure of the magma, which is assumed to be equal to the lithostatic load in this model. On the other hand, this assumption may not be valid under the low Martian surface pressure. Thus, we test the effect using the model by Jaupart and Tait Ž1989.. This model is the opposite extreme of the model by Wilson and Head Ž1981. and assumes that the conduit wall is rigid and the radius of the conduit is constant from the magma chamber to the vent. The pressure of the magma is usually higher than the lithostatic pressure. Because of the geometry of the conduit, the mixture of gas and melt cannot be accelerated beyond a critical value. This is called the choking velocity. The choking velocity, u c , is given by the sound velocity of the mixture of gas phase and pyroclasts ŽJaupart, 1996.: uc s

dr

y1 r2

ž /

Ž 6.

dP

where P is the magma pressure at the vent, r is the mixture density of gas phase and pyroclasts at the vent. Using Eq. Ž5., Eq. Ž6. is expressed by: uc s

P

'RT

1

1

s

ne

½ ž(

(

/

y ne q

(n

e

RT

P

5

Ž 7.

where T is the temperature of magma, n e is the exsolved gas mass fraction, s is the density of the pyroclasts, and R is the gas constant of the volcanic gas. The relationship between the choking velocity and the exsolved gas mass fraction, n e , is shown in Fig. 2. This result is almost independent of the atmospheric pressure because it is very small compared with the vent pressure in this case. For most cases, the eruption velocity is less than ; 150 mrs

T. Kusanagi, T. Matsuir Physics of the Earth and Planetary Interiors 117 (2000) 437–447

Fig. 2. Relationship between the exsolved gas mass fraction and the choking velocity. Pressure at the vent is 10 5 and 10 7 Pa, respectively.

except when the vent pressure is extremely high and exsolved gas fraction is small. After magma erupts out of the vent, it undergoes subsequent pressure release through a series of shocks. This increases the vertical velocity and decreases magma temperature. Since this last process tends to fill the difference between the eruption conditions deduced from the two treatments Že.g., velocity., the eruption conditions calculated from the model of Jaupart and Tait Ž1989. are not very different from those calculated from the model of Wilson and Head Ž1981. except that the eruption temperature is somewhat lower. Thus, we adopt the model by Wilson and Head Ž1981. for the following calculation. 3.2. The eruption cloud The eruption cloud entrains the ambient air during ascent in the atmosphere. The entrained air is heated by the hot pyroclasts in the eruption cloud and expands. If the eruption cloud has enough heat and initial eruption velocity, the cloud gains buoyancy. Once this occurs, the cloud rises very high and forms a convective eruption column. Otherwise, the cloud collapses and falls back on the ground surface, forming a pyroclastic flow fed by a fountain-like structure over the vent.

441

This process has been studied theoretically by a number of researchers Že.g., Wilson et al., 1980; Sparks, 1986.. In this study, we use the formulation by Woods Ž1988. with modification by Sugita and Matsui Ž1998.. Equations of the conservations of mass, momentum and energy are incorporated together with the temperature dependence of the specific heat of gas and pyroclasts. The equation of mass conservation is given by: dF s 2p a rair u e Ž 8. dz where z is the height from the surface, F is the mass flux, a is the radius of the eruption cloud, rair is the density of ambient atmosphere and u e is the inward velocity of the surrounding atmosphere. The mass flux F is defined as: F s p a 2r u

Ž 9.

where u is the vertical velocity and r is the bulk density of the eruption cloud. The density r is given by: 1 1yn nR u s q Ž 10 . r s P where R is the average gas constant of volcanic gas and entrained air, u is the temperature of the eruption cloud, n is the mass fraction of the gas phase in the eruption cloud. Since the mass flux of pyroclastic material is conserved, the relationship between the initial gas mass fraction n 0 and the gas mass fraction at the height z is given by:

Ž 1 y n . F s Ž 1 y n 0 . F0

Ž 11 .

or n s 1 y Ž 1 y n0 .

F0

Ž 12 . F where F0 is the mass flux at the vent. The equation of motion is given by ŽWoods, 1988.: u

u2

du sy dz

8a

(

rair r

y

r y rair r

g

Ž 13 .

The momentum equation can also be expressed based on the buoyancy force as follows: d uF s yg Ž r y rair . p a 2 Ž 14 . dz

T. Kusanagi, T. Matsuir Physics of the Earth and Planetary Interiors 117 (2000) 437–447

442

By substituting Eqs. Ž9. and Ž13. into Eq. Ž14., the equation of mass conservation can be expressed by ŽSugita and Matsui, 1998.: dF

1

s dz

(pr 8

air uF

Ž 15 .

This equation is used as the equation of mass conservation instead of Eq. Ž8..

The energy equation is given by ŽSugita and Matsui, 1998.: d dz

½

HŽu . Fq

u2 F 2

5

s Hair Ž T .

dF dz

y Fg

Ž 16 .

where T is the temperature of the ambient atmosphere. H and Hair is the enthalpy of the eruption cloud and the ambient atmosphere, respectively.

Fig. 3. Heights and temperatures at the top of eruption clouds. Ža. and Žb. are the results for the current Martian conditions. We see a clear distinction between convective eruption clouds and pyroclastic flows. Compared with the calculated results for Earth Žc and d., the height of the fountain feeding a pyroclastic flow on Mars is very small, and the temperature decrease at its top is also small.

T. Kusanagi, T. Matsuir Physics of the Earth and Planetary Interiors 117 (2000) 437–447

Since the entrained ambient air dominates the mass of an eruption cloud, the eruption style is controlled by the vertical structure of the planetary atmosphere. Since the change in the specific heat also plays a very important role in the dynamics of the eruption cloud ŽSugita and Matsui, 1998., this effect is also taken into account. By using the result of the calculation of the magma flow in the conduit as the initial condition, we can estimate how erupted material rises Ži.e., height and thermal structure of an eruption cloud..

443

4. Calculation condition and results We assume basaltic magma with a temperature of 1400 K. Although the viscosity of bubbleless magma depends greatly on the water content, we assume that it is 100 Pa s for simplicity. The densities of the magma and the country rock used in this study are 2500 and 2700 kg my3 , respectively. Under these assumptions, we carried out calculations for two atmospheric conditions, the thin current Martian atmosphere and a thicker CO 2 atmosphere.

3.3. Combined calculation 4.1. Eruption under current Martian atmosphere Combination of the calculations of two stages gives the volcanic eruption conditions on Mars. The conditions are more complex if we consider a collapsed eruption column forming a fountain over the vent as discussed by Wilson and Heslop Ž1990.. However, for simplicity, we do not take into account such effects. In this study, the eruption velocity and exsolved gas fraction are derived from the numerical calculation of the magma ascent in the conduit in which the water content of the magma, the magma temperature, and the vent radius are given as free parameters. Using these values, the calculation for the dynamics of an eruption cloud is carried out to characterize its nature Ži.e., the temperature and density of the eruption cloud at each height and the ultimate height which the eruption cloud reaches.. Thus, we can evaluate the influence of the water content on the eruption style through these calculations.

The current Martian atmosphere is very thin Ž; 600 Pa. and mainly composed of CO 2 . Because of the seasonal variation due to the formation of the polar caps, the pressure fluctuates by 50%. Occasional sand storms also alter the pressure by absorbing the sunlight. The temperature structure of Martian atmosphere is derived from the data obtained by Mariner 9, Vikings 1 and 2, and Mars Pathfinder. We used the temperature structure under a relatively dust-free condition observed by the Viking landers ŽSeiff and Kirk, 1977.. The pressure structure is assumed to be hydrostatic. The result of the calculation for this temperature profile is shown in Fig. 3. Fig. 3a shows that there is a critical gas mass fraction for a given vent radius, above which the height of the cloud increases abruptly to form a convective eruption column.

Fig. 4. Relationship between the water mass fraction of the magma and eruption styles under the current Martian atmosphere.

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T. Kusanagi, T. Matsuir Physics of the Earth and Planetary Interiors 117 (2000) 437–447

Compared with the result of a calculation for the equivalent eruption on Earth, the height of the collapsed fountain after it gets stable is very low on Mars. This is because the Martian atmosphere is so thin that the density of the eruption cloud does not decrease by entrainment of the ambient air into the eruption cloud. In addition, the temperature decrease between the vent and the top of the collapsed column is small. This is also because the cooling due to entrainment is less effective. Consequently, the eruption cloud with low initial velocity stops rising before it gets cooled by entraining the ambient air. Thus, the pyroclastic material in such an eruption cloud will fall on the ground while its temperature is still high. If the pyroclasts are still molten, they will form a lava-like flow. This kind of eruption is observed in Hawaiian type volcanic activity and lavas made in such activities are called clastogenic lavas ŽFrancis, 1993.. On Earth, clastogenic lava is formed at a high eruption rate when the dense lava fountain prevents pyroclasts from being cooled by radiation ŽWilson and Head, 1994.. This is a kind of eruption that is caused by magma disrupted in the conduit but that leaves a lava-like deposit. The condition to cause such an eruption is illustrated in Fig. 3b and d. We assume that the clastogenic lava is formed when the temperature decrease during ascent is less than 50 K. Under a thin atmospheric condition, this kind of eruption is more probable. Taking this clastogenic lava into consideration, the condition to form a lava Žor lava-like. deposit on Mars is that magma contains - 0.25 wt.% water. This value is comparable to the average water content of MORB, about 0.2 wt.%. Fig. 4 shows the relationship between gas mass fraction of magma and eruption style. The overlapping part displays the uncertainty due to the dependence of the eruption style on the vent size.

We used a one-dimensional radiative–convective equilibrium model ŽNakajima et al., 1992. to describe this thicker atmosphere. The composition is assumed to be 100% CO 2 and the surface pressure is 1 bar. Fig. 5 shows the result of eruption calculations under a thick CO 2 atmosphere. Pyroclastic flows reach relatively high altitudes and are cooled effectively. These flows are unlikely to form lava-like deposit when they fall on the ground. The eruption style under this thick atmosphere is shown in Fig. 6.

4.2. Eruption under 1-bar Martian atmosphere The southern hemisphere of Mars has unique fluvial features that are thought to have been formed by running water Že.g., Baker, 1982.. Continuous flow of water requires a relatively high surface temperature ŽPollack et al., 1987.. Thus, Mars may once have had a thicker atmosphere than today.

Fig. 5. Ža. Heights and Žb. temperatures at the top of eruption clouds under an ancient 1 bar CO 2 atmosphere.

T. Kusanagi, T. Matsuir Physics of the Earth and Planetary Interiors 117 (2000) 437–447

445

Fig. 6. Relationship between the water mass fractions of magma and eruption styles under an ancient 1 bar CO 2 atmosphere. The range of water mass fraction of magma that can result in a lava-forming eruption is almost the same as that under the current thin atmosphere.

A comparison of Figs. 4 and 6 suggests that the conditions for lava-forming eruptions Žboth gas-free eruptions and clastogenic lava-forming eruptions. under an ancient 1 bar atmosphere are not so different from those in the current atmosphere despite the fact that the water content to cause magma disruption is about one order of magnitude larger. The minimum magma water content to generate explosive eruptions under a 1-bar atmosphere is about 0.05 wt.%.

5. Water content of the Martian mantle We can evaluate the water content of Martian mantle based on the geological features and the historical change in the volcanic eruption styles. There are two major candidates for the cause of such changes in volcanism. One is the change in volatile content in the Martian mantle. If water in the Martian mantle has decreased with time, it would have reduced the explosivity of the Martian volcanoes. The other is the change in the atmospheric conditions. As was shown in the numerical results, this alters the nature of the eruption condition considerably. Scambos and Jakosky Ž1990. estimated that the release factor of nonradiogenic volatiles Že.g., water. from the Martian interior since the end of its formation is 0.017–0.112. Such a release factor is too small to cause a change in volatile content in the Martian mantle that is sufficient to change the style of volcanic eruptions by itself Ža release factor of 0.5 is needed from the calculation above..

This suggests that the change in eruption style is due to the change in atmospheric conditions on Mars. On the basis of this assumption, we can obtain a lower limit for the water content required for explosive volcanism under a thick ancient Martian atmosphere Ž1 bar pressure., and similarly the upper limit required for more effusive volcanism under the current thin atmosphere. We have estimated these values in Sections 4.1 and 4.2. The estimated lower limit is 0.05 wt.% and the upper limit is 0.25 wt.%. However, the estimated water content may be one order of magnitude smaller when we consider the fact that basalt typically represent 10% partial melting. In this case, the value of 0.05–0.25 wt.% might be regarded as a maximum estimate. In former studies, the water content of the Martian mantle has been evaluated from chemical inforŽ1987. estimated the mation. Dreibus and Wanke ¨ water content of the Martian mantle to be 36 ppm from two component model for the formation of Mars. This estimated value is far smaller than that of terrestrial basaltic magma Ž0.2–1 wt.% on average ŽScarth, 1994... An alternative way to estimate the water content of the Martian mantle is from the SNC meteorites. Simple measurement of the water contents in SNC meteorites gives a value between 130 and 350 ppm ŽMcSween and Harvey, 1993.. The magmas that formed the SNC meteorites, however, are thought to have experienced degassing on their way from the magma reservoir to the Martian surface, so this value may not give the proper estimate for the Martian mantle. Treiman Ž1985. estimated that the amphibole

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T. Kusanagi, T. Matsuir Physics of the Earth and Planetary Interiors 117 (2000) 437–447

content occupies 5–10% of the inclusions in some SNC meteorites and concluded that the original magma must have contained at least 0.1–0.2 wt.% water, because the amphibole contains ; 2 wt.% water. On the other hand, by considering the solidification process of the magma which formed the SNC meteorites, the water content of Martian mantle was estimated to be about 1.4 wt.% ŽJohnson et al., 1991; McSween and Harvey, 1993.. Our estimate for the water content of Martian mantle Ž0.05–0.25 wt.%. is in the range of the estimates based on SNC meteorites. This is consistent with the presumption that SNC meteorites are Martian igneous rocks ejected by the impacts of other meteorites. The fact that previous chemical evaluations for water content and estimates based on geologic features in this study show remarkable agreement reinforces the validity of the assumption that the change in volcanic eruption style is caused by epochal climate change on Mars.

Acknowledgements We thank S. Sugita for his valuable comments on the early version of this paper, which is useful for the improvement of the paper. We appreciate the kind and helpful reviews of Lionel Wilson and an anonymous reviewer.

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T. Kusanagi, T. Matsuir Physics of the Earth and Planetary Interiors 117 (2000) 437–447 gotty and Zagami: magmatic water, depth of crystallization, and metasomatism. Meteoritics 20, 229–243. Wilson, L., Head, J.W. III, 1981. Ascent and eruption of basaltic magma on the Earth and Moon. J. Geophys. Res. 86, 2971– 3001. Wilson, L., Head, J.W. III, 1994. Mars: review and analysis of volcanic eruption theory and relationships to observed landforms. Rev. Geophys. 32, 221–263. Wilson, L., Heslop, S.E., 1990. Clast sizes in terrestrial and

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Martian ignimbrite lag deposits. J. Geophys. Res. 95, 17309– 17314. Wilson, L., Sparks, R.S.J., Walker, G.P.L., 1980. Explosive volcanic eruptions: IV. The control of magma properties and conduit geometry on eruption column behavior. Geophys. J. R. Astron. Soc. 63, 117–148. Woods, A.W., 1988. The fluid dynamics and thermodynamics of eruption columns. Bull. Volcanol. 50, 169–193.

letters to nature lavas 5 km thick, then our estimates of the total quantity of lava erupted over the past ,4 Gyr (including volcanic edi®ces) must be revised from the 7 3 107 km3 calculated previously20 to 5 3 108 km3 . Alternatively, the lava could be less extensive if the formation of Valles Marineris was intimately associated with the presence of a thick lava sequence, which thins rapidly away from the canyons. If deep layering is con®ned to the area of a rectangle enclosing the canyons (,4 3 106 km2 ) and is 10 km thick, then the volume is 4 3 107 km3 . This alone greatly exceeds a previous estimate of 8 3 106 km3 of magma extruded in the Late Noachian20. We conclude that volcanism on early Mars was probably much more voluminous than previously documented, and that it must have affected the climate and near-surface environment. Pollack et al.21 proposed that a warm, wet climate on early Mars was sustained by a thick CO2 atmosphere, which must be continuously resupplied or recycled to balance loss of CO2 to carbonates. Two mechanisms for recycling the CO2 have been proposed: extensive volcanism21 and impacts22. If the recycling was mainly from impacts, then the warm, wet conditions corresponded to the time (on Earth) of heavy bombardment and the impact frustration of life23. Extensive volcanism on Mars could have maintained a thick atmosphere for a signi®cant period of time after the heavy bombardment21. The layers seen by MOC provide evidence for voluminous volcanism; but a thick atmosphere could have been sustained only if suf®cient carbonates exist in the crust of Mars, which has not yet been con®rmed16. M Received 16 September; accepted 21 December 1998. 1. Lucchitta, B. K. et al. in Mars (eds Kieffer, H. H., Jakosky, B. M., Snyder, C. M. & Matthews, M. S.) 453±492 (Univ. Arizona Press, Tucson, 1992). 2. Tanaka, K. L., Scott, D. H. & Greeley, R. in Mars (eds Kieffer, H. H., Jakosky, B. M., Snyder, C. M. & Matthews, M. S.) 345±382 (Univ. Arizona Press, Tucson, 1992). 3. Clifford, S. M. A model for the hydrologic and climatic behavior of water on Mars. J. Geophys. Res. 98, 10973±11016 (1993). 4. Tanaka, K. L. & Golombek, M. P. Martian tension fractures and the formation of graben and collapse features at Valles Marineris. Proc. Lunar Planet. Sci. Conf. 19, 383±396 (1989). 5. Davis, P. A. & Golombek, M. P. Discontinuities in the shallow Martian crust at Lunae, Syria, and Sinai Plana. J. Geophys. Res. 95, 14231±14248 (1990). 6. Zuber, M. T. & Aist, L. L. The shallow structure of the Martian lithosphere in the vicinity of the ridged plains. J. Geophys. Res. 95, 14215±14230 (1990). 7. Malin, M. C. et al. Mars Observer Camera. J. Geophys. Res. 97, 7699±7718 (1992). 8. Malin, M. C. et al. Early views of the Martian surface from the Mars Orbital Camera of Mars Global Surveyor. Science 279, 1681±1685 (1998). 9. Albee, A. L., Palluconi, F. D. & Arvidson, R. E. Mars Global Surveyor mission: Overview and status. Science 279, 1671±1672 (1998). 10. Lucchitta, B. K. Morphology of chasma walls, Mars. J. Res. US Geol. Surv. 6, 651±662 (1978). 11. Geissler, P. E., Singer, R. B. & Lucchitta, B. K. Dark materials in Valles Marineris: Indications of the style of volcanism and magmatism on Mars. J. Geophys. Res. 95, 14399±14413 (1990). 12. Scott, D. H. & Tanaka, K. L. Geologic Map of the Western Equatorial Region of Mars, Scale 1:15,000,000 (Misc. Inv. Ser. Map I-1802-A, US Geol. Surv., Denver, 1986). 13. Witbeck, N. E., Tanaka, K. E. & Scott, D. H. Geologic Map of the Valles Marineris Region of Mars, Scale 1:2,000,000 (Inv. Ser. Map I-2010, US Geol. Surv., Denver, 1991). 14. Erard, S. et al. Spatial variations in composition of the Valles Marineris and Isidis Planitia regions of Mars derived from ISM data. Proc. Lunar Planet. Sci. Conf. 21, 437±456 (1991). 15. Self, S., Thordarson, T. & Keszthelyi, L. in Large Igneous Provinces (eds Mahoney, J. J. & Cof®n, M. F.) 381±410 (Am. Geophys. Union, Washington, D. C., 1997). 16. Christensen, P. R. et al. Results from the Mars Global Surveyor thermal Emission Spectrometer. Science 279, 1692±1698 (1998). 17. Schubert, G., Solomon, S. C., Turcotte, D. L., Drake, M. J. & Sleep, N. H. in Mars (eds Kieffer, H. H., Jakosky, B. M., Snyder, C. M. & Matthews, M. S.) 147±183 (Univ. Arizona Press, Tucson, 1992). 18. Carr, M. H. Water on Mars (Oxford Univ. Press, New York, 1996). 19. Craddock, R. A., Maxwell, T. A. & Howard, A. D. Crater morphometry and modi®cation in the Sinus Sabaeus and Margaritifer Sinus regions of Mars. J. Geophys. Res. 102, 13321±13340 (1997). 20. Greeley, r. & Schneid, B. D. Magma generation on Mars: Amounts, rates, and comparisons with Earth, Moon, and Venus. Science 254, 996±998 (1991). 21. Pollack, J. B., Kasting, J. F., Richardson, S. M. & Poliakoff, K. The case for a wet, warm climate on early Mars. Icarus 71, 203±224 (1987). 22. Carr, M. H. Recharge of the early atmosphere of Mars by impact-induced release of CO2. Icarus 79, 311±327 (1989). 23. Maher, K. A. & Stevenson, D. J. Impact frustration of the origin of life. Nature 331, 612±614 (1988). 24. Topographic Maps of the Polar, Western, and Eastern regions of Mars (Misc. Inv. Ser. Map I-2160, US Geol. Surv., Denver, 1991). 25. Fanale, F. P. Martian volatiles: Their degassing history and geochemical fate. Icarus 28, 179±202 (1976). 26. Soderblom, L. A. & Wenner, D. B. Possible fossil water liquid±ice interfaces in the Martian crust. Icarus 34, 622±637 (1978). 27. Treiman, A. H., Fuks, K. H. & Murchie, S. Diagenetic layers in the upper walls of Valles Marineris, Mars: Evidence for drastic climate change since the mid-Hesperian. J. Geophys. Res. 100, 26339±26344 (1995). Acknowledgements. We thank L. Keszthelyi for discussions, and M. T. Zuber and N. G. Barlow for comments on the manuscript. This work was supported by the MGS project. Correspondence and requests for materials should be addressed to A.S.M. (e-mail: [email protected]).

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Evidence for recent volcanism on Mars from crater counts William K. Hartmann*, Michael Malin², Alfred McEwen³, Michael Carr§, Larry Soderblomk, Peter Thomas¶, Ed Danielson#, Phillip JamesI & Joseph Veverka¶ * Planetary Science Institute, Tucson, Arizona 85705, USA ² Malin Space Science Systems, San Diego, California 92191, USA ³ Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona 85721, USA § US Geological Survey, Menlo Park, California 94025, USA k US Geological Survey, Flagstaff, Arizona 86001, USA ¶ Cornell University, Ithaca, New York 14853, USA # California Institute of Technology, Pasadena, California 91125, USA I University of Toledo, Toledo, Ohio 43606, USA .........................................................................................................................

Impact craters help characterize the age of a planetary surface, because they accumulate with time. They also provide useful constraints on the importance of surface erosion, as such processes will preferentially remove the smaller craters. Earlier studies of martian crater populations revealed that erosion and dust deposition are important processes on Mars1±6. They disagreed, however, on the age of the youngest volcanism7,8. These earlier studies were limited by image resolution to craters larger than a few hundred metres in diameter. Here we report an analysis, using new images obtained by the Mars Global Surveyor spacecraft, of crater populations that extend the size distribution down to about 16 m. Our results indicate a wide range of surface ages, with one regionÐlava ¯ows within the Arsia Mons calderaÐ that we estimate to be no older than 40±100 million years. We suggest that volcanism is a continuing process on Mars. The distribution of crater numbers versus crater diameter on lunar lava plains, called the `production function', represents the shape of the population of craters being produced on the moon in current geological time. Its shape is well determined9±11. Our initial step was to test whether the production function observed on young, well-preserved surfaces on Mars is the same as that found on the Moon. This result has been found for craters larger than 1 km in diameter, but has not been well tested for the steep branch below 1 km (ref. 7) (see ®gures). Dashed reference lines in the shape of the lunar production function are shown in each of the crater count diagrams in this Letter, along with an upper solid line that marks the crater density on the most heavily cratered surfaces in the Solar System, dated about 4.0 Gyr old on the Moon, and believed to mark the saturation equilibrium condition where new craters erase old craters10,12. These reference lines allow the comparison of the Mars counts with the lunar production function. Here we report our analyses of images obtained by the Mars Orbiter Camera (MOC) on board the Mars Global Surveyor spacecraft. Martian crater counts obtained from the MOC images are a signi®cant advance over previously published data, and the images reveal the importance of mobile dust in shaping the martian landscape and softening the pro®le of craters13,14. In general, our procedure is to count all craters but avoid areas with obvious clusters of small secondary ejecta craters. To study the crater size distribution in a relatively young area, we chose a MOC image that crosses a strip of the ¯oor of the summit caldera of the very young Tharsis volcano, Arsia Mons. Figure 1a shows some of this surface, and the crater counts obtained on Arsia Mons and its summit caldera are given in Fig. 1b. The largest crater within the summit caldera is barely 1 km across, and so the counts are extended to larger sizes (using open symbols) with additional counts from the ¯anks of Arsia Mons. These counts (caldera and whole volcano) each appear consistent with the shape of the lunar crater diameter

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letters to nature distribution, and support the contention that the recent martian production function matches that of the Moon at all observed sizes. At the upper left of Fig. 1b, the curve intersects the proposed saturation equilibrium line (shown solid) at diameter D < 60 m. This behaviour is analogous to that found in the lunar maria, where the steep branch hits the saturation line at D < 300 m. These data contain age information. The reference lines (Fig. 1b) show that the crater density in the summit caldera is only 2±10% of that found in the lunar maria; the crater density on the outer slopes may be roughly 3±10 times that. Our interpretation is that the caldera lavas are relatively young and that no substantial obliterative losses have occurred for craters down to D ˆ 60 m, or depths as shallow as ,10 m. A review12 of asteroid and cometary data and cratering physics suggests that the actual martian crater production rate in recent geological time is 1±4 times the mean post-mare lunar rate, with a best estimate of 2. This best estimate yields an age estimate for Arsia Mons caldera lava ¯ows of roughly 40±200 Myr, and the outer ¯ank ages would be several times older, with uncertainties of a factor of 2±3. The good match between the slope of the martian and the lunar crater diameter distributions, at 60 m , D , 1 km, indicates that there has not been enough dust in®ll in this region to remove many craters larger than 60 m. Nonetheless, although the altitude is ,26 km above the mean surface of Mars, we see direct evidence for some dust deposition in certain areas on the caldera rim. Figure 2 shows a portion of MOC image no. 3308 in a region of horst± graben structure just outside the north caldera rim of Arsia Mons. Rilles and other textures are clearly seen on the horst surfaces, but are muted or covered entirely by smooth deposits on the lower graben ¯oors, especially in smooth drifts banked against the edges of the grabens. The dust source may be fallout from global dust storms that inject dust into layers as high as 35±40 km in the martian atmosphere15,16.

Figure 1 Crater density on Arsia Mons. a, Portion of MOC image no. 3308, showing portion of summit caldera ¯oor on Arsia Mons. b, Crater counts for the caldera ¯oor and ¯anks of Arsia Mons, superimposed on reference lines scaled to crater populations on lunar lava plains. The two short solid lines represent the stratigraphic de®nition of the division between three eras of Martian history: Amazonian (lower part of graph), Hesperian (between the lines) and Noachian. The counts suggest that the caldera ¯oor is younger than the ¯anks of the volcano. (The crater counts were obtained from the images by more than one person, to avoid bias and to test repeatability; the name of the person is given in

Figure 2 Horst±graben structure concentric with Arsia Mons caldera rim. Parts of

the key.)

graben ¯oors show evidence of dust deposits. See text for details.

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letters to nature An additional issue clari®ed by these data involves the minimum crater size on Mars. Viking lander analysts concluded that the crater population cut off below diameter D ˆ 50 m, due to atmospheric breakup of bolides17. The MOC images give the ®rst chance to test that prediction. We ®nd no cut-off down to D < 16 m. Many local regions are resurfaced by dust drifts and have few small craters, but other nearby areas show old surfaces where crater numbers increase smoothly as D decreases, down to 16 m and less. The comparison between young areas and ancient upland areas

on Mars is striking. Figure 3a shows a moderately heavily cratered upland area near Nirgal Vallis in MOC image no. 605, and crater counts are given in Fig. 3b. Figure 4a shows a heavily cratered terrain in MOC image no. 2303 on the ¯oor of the crater Schiaparelli, a large, old crater which in turn is superposed on one of the most heavily cratered martian terrains, Arabia Terra; crater counts are given in Fig. 4b. As is characteristic of all heavily cratered areas, the crater counts for both these areas show a pronounced ¯attening of the primary crater branch from 1 km , D , 45 km. This ¯attening

Figure 3 Crater density in the area around Nirgal Vallis. a, Moderate crater density

Figure 4 Crater density in the area around the crater Schiaparelli. a, Portion of MOC

in plains adjacent to Nirgal Vallis, in MOC image no. 605. We note the degraded

image no. 2303 showing heavily cratered portions of the ¯oor of the crater

states of some craters. b, As in Fig. 1b but for the older upland region around

Schiaparelli. Many craters are severely degraded. b, As in Fig.1b but for the ¯oor of

Nirgal Vallis, including area of image a. The solid, bent line is a calculated steadystate line showing the OÈpik effect for craters with constant net dust deposition of

crater Schiaparelli and the surrounding old region of Arabia Terra, including area

10-6 m yr-1 (W.K.H., unpublished results). The counts suggest an old surface, more

surface is probably ,4 Gyr old. Schiaparelli appears somewhat younger, perhaps

than 3 Gyr old, in which smaller craters have been lost by obliterative processes,

3±4 Gyr old. Smaller craters in this region have apparently been lost by obliterative

such as dust in®ll.

effects; the oldest visible 20-m craters may date back no more than ,10 Myr.

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of image a. The largest craters in Arabia Terra appear near saturation, and the

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letters to nature È pik as early as 1965 and was attributed by him to was detected by O deposition of material in craters, preferentially obliterating small craters1. It has subsequently been interpreted as evidence of longterm erosion, deposition, and lava ¯ooding of martian craters, especially in the earlier parts of Mars' history2±6, although it has also been suggested that the early production function on Mars was ¯atter than the present function18. Our MOC data show that the steep branch of the curve in old areas also appears distinctly ¯atter than on the Moon; in addition, the MOC images (Figs 3a and 4a) reveal a range of degradation states among 100-m-scale craters. These states range from fresh craters to craters with dune deposits on the ¯oor, to craters whose ¯oors are ®lled and whose rims barely protrude above the dust. This ®ts the view that small craters have been lost by dust in®ll and blanketing, and the ¯attening of the production-function curves, at least at small diameters, is thus È pik effect. attributed to the O The heavy, bent, solid line in Figs 3b and 4b is a predicted steadyÈ pik effect in®lling of craters. This curve is state line for the O generally derived in refs 3 and 4, but has been modi®ed by unpublished calculations of one of us (W.K.H.), taking into account the depth±diameter relation for fresh martian craters18. The average net deposition rate in crater ¯oors, assumed in this curve, is ,10-6 m yr-1, consistent with other estimates2±7,14. The predicted curve is a good ®t for the data. The conclusion is that on the oldest martian uplands, smaller craters are probably in a rough equilibrium with local obliteration processes, at least if we average over large enough areas. A similar statement applies to Earth, but with higher obliteration rates. The comparison of crater size distributions on the old surfaces and young lava surfaces of Mars, and the lunar mare lava plains, indicates the wide range of surface ages on Mars, relative to the Moon; this comparison supports a conclusion that the youngest large-scale lava eruptions on Mars are much younger than on the Moon, having occurred in the last few per cent of martian time. The discovery of martian basaltic meteorites with crystallization ages of 1.3 Gyr or younger19 supports this conclusion. The crater statistics that we report here suggest that volcanism is continuing on Mars in current geological time. M Received 16 September; accepted 14 December 1998. È pik, E. J. Mariner IV and craters on Mars. Irish Astron. J. 7, 92±104 (1965); The Martian surface. 1. O Science 153, 255±265 (1966). 2. Hartmann, W. K. Martian cratering (Paper I). Icarus 5, 565±576 (1966). 3. Chapman, C., Pollack, J. & Sagan, C. An Analysis of the Mariner 4 Photography of Mars (Spec. Rep. 268, Smithson. Astrophys. Obs., 1968). 4. Hartmann, W. K. Martian cratering III: Theory of crater obliterations. Icarus 15, 410±428 (1971). 5. Jones, K. L. Evidence for an episode of crater obliteration intermediate in Martian history. J. Geophys. Res. 79, 3917±3931 (1974). 6. Chapman, C. R. Cratering on Mars. I. Cratering and obliteration history. Icarus 22, 272±291 (1974). 7. Hartmann, W. K. Martian cratering, IV: Mariner 9 initial analysis of cratering chronology. J. Geophys. Res. 78, 4096±4116 (1973). 8. Neukum, G. & Hiller, K. Martian ages. J. Geophys. Res. 86, 3097±3121 (1981). 9. Strom, R. G., Croft, S. K. & Barlow, N. G. in Mars (ed. Kieffer, H.) 383±423 (Univ. Arizona Press, Tucson, 1992). 10. Hartmann, W. K. Planetary cratering 1. Lunar highlands and tests of hypotheses on crater populations. Meteoritics 30, 451±467 (1995). 11. Plaut, J., Kahn, R., Guiness, E. & Arvidson, R. Accumulation of sedimentary debris in the south polar region of Mars and implications for climate history. Icarus 76, 357±377 (1988). 12. Hartmann, W. K. et al. in Basaltic Volcanism on the Terrestrial Planets (eds Basaltic Volcanism Study Project) 1050±1129 (Pergamon, Elmsford, NY, 1981). 13. Hartmann, W. K. & Gaskell, R. W. Planetary cratering 2: Studies of saturation equilibrium. Meteorit. Planet. Sci. 32, 109±121 (1996). 14. Malin, M. C. et al. Early views of the Martian surface from the Mars Orbiter camera of Mars Global Surveyor. Science 279, 1681±1685 (1998). 15. Binder, A. B. et al. The geology of the Viking 1 lander site. J. Geophys. Res. 82, 4439±4451 (1977). 16. Gault, D. E. & Baldwin, B. S. Impact cratering on Mars: some effects in the atmosphere. Eos 51, 343 (1970). 17. Carr, M. H. & Viking Orbiter Team Viking Orbiter View of Mars (Spec. Publ. 441, NASA Washington DC, 1980). 18. Cinala, M. J. in Impact and Explosion Cratering (eds Roddy, D. J., Pepin, R. O. & Merrill, R. B.) 575± 592 (Pergamon, Elmsford, NY, 1977). 19. Nyquist, L. et al. A single-crater origin for Martian shergottites: Resolution of the age paradox? Lunar Planet. Sci. 29, 1688 (1998). Acknowledgements. We thank G. Herres, G. Esquerdo, and, in Madrid, J. Anguita and M. de las Casas, for assistance with crater counts and data processing. We also thank D. Berman and G. Hartmann for editorial assistance. Correspondence and requests for materials should be addressed to W.K.H. (e-mail: [email protected]).

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Groundwater formation of martian valleys Michael C. Malin* & Michael H. Carr² * Malin Space Science Systems, PO Box 910148, San Diego, California 92191-0148, USA ² US Geological Survey, 345 Middle®eld Road, Menlo Park, California 94025, USA

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The martian surface shows large out¯ow channels, widely accepted as having been formed by gigantic ¯oods that could have occurred under climatic conditions like those seen today1±5. Also present are branching valley networks that commonly have tributaries1±8. These valleys are much smaller than the out¯ow channels and their origins and ages have been controversial. For example, they might have formed through slow erosion by water running across the surface, either early or late in Mars' history9±13, possibly protected from harsh conditions by ice cover14±16. Alternatively, they might have formed through groundwater or ground-ice processes that undermine the surface and cause collapse, again either early or late in Mars' history3,4. Longduration surface runoff would imply climatic conditions quite different from the present environment. Here we present highresolution images of martian valleys that support the view that ground water played an important role in their formation, although we are unable as yet to establish when this occurred. Images acquired by the Mars Orbiter Camera (MOC) during the aerobraking phase (September 1997 to February 1998) of the Mars Global Surveyor mission typically have resolutions in the range 4± 8 m per pixel, in most cases a factor of 20±50 times better than previous imaging17,18. The images reveal new details about the valleys that strongly support an origin by ¯uid erosion. Although apparent drainage networks are observed locally, dissection of the adjacent upland surface, as might be expected if the ¯uid had an atmospheric rather than a subsurface source, is not seen. The lack of eroded uplands adjacent to martian ¯uvial valleys and the implication for a localized water source was previously noted in studies of Viking Orbiter images19,20. Figure 1 is an image of Nanedi VallisÐan 800-km-long valley that appears incised into cratered plains north of the Valles Marineris. Nanedi Vallis is one of the longest and freshest-appearing of the martian valley networks. Despite its length it has only a few short tributaries, and no obvious catchment area. It starts close to the equator at 498 W in an area where there is other evidence for groundwater action, including the source of the out¯ow channel, Shalbatana Vallis. The circuitous path of the valley seen here appears to have been inherited from sur®cial ¯uid movement, although the source of the ¯uid is not apparent. Such arcuate and reversing paths are dif®cult, if not impossible, to create by headward erosion (that is, progressively upstream towards the source) of a stream, lending support to an interpretation, based on visual appearance, that the valley formed by entrenchment of an originally meandering ¯ow. This interpretation is further strengthened by the observation of an interior channel, presumably the speci®c course of the valleyforming ¯uid. However, as with many entrenched valley systems on Earth, mass movements accompanying groundwater action are likely to have created much of the relief and width of the presently observed valley. It could be argued that valley formation re¯ected groundwater processes fed by precipitation, and that the lack of dissection of the adjacent plain is the result of high permeability of the near-surface materials21. However, the total absence of metrescale dissection here and elsewhere on Mars, and the near-absence of upstream tributaries (suggesting a spatially limited source), support a subsurface rather than atmospheric source. These MOC images show clearly that the uncratered and often

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ExoMars Searching for Life on the Red Planet

ExoMars

Jorge Vago, Bruno Gardini, Gerhard Kminek, Pietro Baglioni, Giacinto Gianfiglio, Andrea Santovincenzo, Silvia Bayón & Michel van Winnendael Directorate for Human Spaceflight, Microgravity and Exploration Programmes, ESTEC, Noordwijk, The Netherlands

stablishing whether life ever existed on Mars, or is still active today, is an outstanding question of our time. It is also a prerequisite to prepare for future human exploration. To address this important objective, ESA plans to launch the ExoMars mission in 2011. ExoMars will also develop and demonstrate key technologies needed to extend Europe’s capabilities for planetary exploration.

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Mission Objectives ExoMars will deploy two science elements on the Martian surface: a rover and a small, fixed package. The Rover will search for signs of past and present life on Mars, and characterise the water and geochemical environment with depth by collecting and analysing subsurface samples. The fixed package, the Geophysics/Environment Package (GEP), will measure planetary geophysics parameters important for understanding Mars’s evolution and habitability, identify possible surface hazards to future human missions, and study the environment. The Rover will carry a comprehensive suite of instruments dedicated to exobiology and geology: the Pasteur payload. It will travel several kilometres searching for traces of life, collecting and analysing samples from inside surface rocks and by drilling down to 2 m. The very powerful combination of mobility and accessing locations where organic molecules may be well-preserved is unique to this mission.

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ExoMars will also pursue important technology objectives aimed at extending Europe’s capabilities in planetary exploration. It will demonstrate the descent and landing of a large payload on Mars; the navigation and operation of a mobile scientific platform; a novel drill to obtain subsurface samples; and meet challenging planetary protection and cleanliness levels necessary to achieve the mission’s ambitious scientific goals.

The Search for Life Exobiology, in its broadest terms, denotes the study of the origin, evolution and distribution of life in the Universe. It is well established that life arose very early on the young Earth. Fossil records show that life had already attained a large degree of biological sophistication 3500 million years ago. Since then, it has proved extremely adaptable, colonising even the most disparate ecological habitats, from the very cold to the very hot, and spanning a wide range of pressure and chemical conditions. For organisms to have emerged and evolved, water must have been readily available on our planet. Life as we know it relies, above all else, upon liquid water. Without it, the metabolic activities of living cells are not possible. In the absence of water, life either ceases or slips into quiescence. Mars today is cold, desolate and dry. Its surface is highly oxidised and exposed to sterilising and degrading ultraviolet (UV) radiation. Low temperature and pressure preclude the existence of liquid water; except, perhaps, in localised environments, and then only episodically. Nevertheless, numerous features such as large channels, dendritic valley networks, gullies and

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sedimentary rock formations suggest the past action of surface liquid water on Mars – and lots of it. In fact, the sizes of outflow channels imply immense discharges, exceeding any floods known on Earth. Mars’s observable geological record spans some 4500 million years. From the number of superposed craters, the oldest terrain is believed to be about 4000 million years old, and the youngest possibly less than 100 million years. Most valley networks are ancient (3500–4000 million years), but as many as 25–35% may be more recent. Today, water on Mars is only stable as ice at the poles, as permafrost in widespread underground deposits, and in trace amounts in the atmosphere. From a biological perspective, past liquid water itself motivates the question of life on Mars. If Mars’ surface was warmer and wetter for the first 500 million years of its history, perhaps life arose independently there at more or less the same time as it did on Earth. An alternative pathway may have been the transport of terrestrial organisms embedded in meteoroids, delivered from Earth. Yet another hypothesis is that life may have developed within a warm, wet subterranean environment. In fact, given the discovery of a flourishing biosphere a kilometre below Earth’s surface, a similar vast microbial community may be active on Mars, forced into that ecological niche by the disappearance of a more benign surface environment. The possibility that life may have evolved on Mars during an earlier period surface water, and that organisms may still exist underground, marks the planet as a prime candidate in the search for life beyond Earth.

Hazards for Manned Operations on Mars Before we can contemplate sending astronauts to Mars, we must understand and control any risks that may pose a threat to a mission’s success. We can begin to assess some of these risks with ExoMars. Ionising radiation is probably the single most important limiting factor for human interplanetary flight. To evaluate its danger and to define efficient mitigation strategies, it is desirable to incorporate radiation-monitoring capabilities during cruise, orbit and surface operations on precursor robotic missions to Mars. Another physical hazard may result from the basic mechanical properties of the Martian soil. Dust particles will invade the interior of a spacecraft during surface operations, as shown during Apollo’s operations on the Moon. Dust inhalation can pose a threat to astronauts on Mars, and even more so under microgravity during the return flight to Earth. Characteristics of the soil, including the sizes, shapes and compositions of individual particles, can be studied with dedicated in situ instrumentation. However, a more in-depth assessment, including a toxicity analysis, requires the return of a suitable Martian sample. Reactive inorganic substances could present chemical hazards on the surface. Free radicals, salts and oxidants are very aggressive in humid conditions such as the lungs and eyes. Toxic metals, organics and pathogens are also potential hazards. As with dust, chemical hazards in the soil will contaminate the interior of a spacecraft during surface operations. They could damage the health of astronauts and the www.esa.int

A Mars Express image of the Ares Vallis region, showing evidence of ancient, vast water discharges. This immense channel, 1400 km long, empties into Chryse Planitia, where Mars Pathfinder landed in 1997. (ESA/DLR/FU Berlin, G. Neukem)

The ExoMars Rover will be able to drill down to 2 m for samples

Searching for Signs of Life

operation of equipment. Many potential inorganic and organic chemical hazards may be identified with the ExoMars search-for-life instruments.

Geophysics Measurements The processes that have determined the long-term ‘habitability’ of Mars depend on the geodynamics of the planet, and on its geological evolution and activity. Important issues still need to be resolved.

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What is Mars’ internal structure? Is there any volcanic activity on Mars? The answers may allow us to extrapolate into the past, to estimate when and how Mars lost its magnetic field, and the importance of volcanic outgassing for the early atmosphere. ExoMars will also carry the Geophysics/ Environment Package, accommodated on the Descent Module and powered by a small radioisotope thermal generator.

If life ever arose on the Red Planet, it probably did so when Mars was warmer and wetter, during its initial 500– 1000 million years. Conditions then were similar to those on early Earth: active volcanism and outgassing, meteoritic impacts, large bodies of liquid water, and a mildly reducing atmosphere. We may reasonably expect that microbes quickly became global. Nevertheless, there is inevitably a large measure of chance involved in finding convincing evidence of ancient, microscopic life forms. On Earth’s surface, the permanent presence of running water, solar-UV radiation, atmospheric oxygen and life itself quickly erases all traces of any exposed, dead organisms. The only opportunity to detect them is to find their biosignatures encased in a protective environment, as in suitable rocks. However, since high-temperature metamorphic processes and plate tectonics have reformed most ancient terrains, it is very difficult to find rocks on Earth older than 3000 million years in good condition. Mars, on the other hand, has not suffered such widespread tectonic activity. This means there may be rock formations from the earliest period of Martian history that have not been exposed to high-temperature recycling. Consequently, well-preserved ancient biomarkers may still be accessible for analysis. Even on Earth, a major difficulty in searching for primitive life is that, in essence, we are looking for the remnants of minuscule beings whose fossilised forms can be simple enough to be confused with tiny mineral precipitates. This issue lies at the heart of a heated debate among

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Mission strategy to achieve ExoMars’s scientific objectives: 1

To land on, or be able to reach, a location with high exobiology interest for past and/or present life signatures, i.e. access to the appropriate geological environment.

2 To collect scientific samples from different sites, using a Rover carrying a drill capable of reaching well into the soil and surface rocks. This requires mobility and access to the subsurface. 3 At each site, to conduct an integral set of measurements at multiple scales: beginning with a panoramic assessment of the geological environment, progressing to smaller-scale investigations on interesting surface rocks using a suite of contact instruments, and culminating with the collection of well-selected samples to be studied by the Rover’s analytical laboratory. 4 To characterise geophysics and environment parameters relevant to planetary evolution, life and hazards to humans. To arrive at a clear and unambiguous conclusion on the existence of past or present life at the Rover sites, it is essential that the instrumentation can provide mutually reinforcing lines of evidence, while minimising the opportunities for alternative interpretations. It is also imperative that all instruments be carefully designed so that none is a weak link in the chain of observations; performance limitations in an instrument intended to confirm the results obtained by another should not generate confusion and discredit the whole measurement. The science strategy for the Pasteur payload is therefore to provide a self-consistent set of instruments to obtain reliable evidence, for or against, the existence of a range of biosignatures at each search location. Spacecraft:

Carrier plus Descent Module (including Rover and GEP) Data-relay provided by NASA

Launch:

May–June 2011, from Kourou on Soyuz-2b (backup 2013)

Arrival:

June 2013 (backup 2015)

Landing:

Direct entry, from hyperbolic trajectory, after the dust storm season. Latitudes 15˚S–45˚N, all longitudes, altitude: <0 m, relative to the MGS/MOLA* zero level

Science:

Rover with Pasteur payload: mass 120–180 kg, includes: Drill System/SPDS and instruments (8 kg); lifetime 180 sols Geophysics Environment Package (GEP): mass <20 kg; includes: instruments (~4 kg); lifetime 6 years

Ground Segment:

Mission control and mission operations: ESOC Rover operation on Mars surface: Rover Operations Centre GEP operations: to be decided

*MGS/MOLA: Mars Global Surveyor/Mars Orbiter Laser Altimeter

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palaeobiologists. It is therefore doubtful that any one signature suggestive of life – whether it is an image implying a biostructure, an interesting organic compound or a fractionated isotopic ratio – may reliably demonstrate a biogenic origin. Several independent lines of evidence are required to construct a compelling case. ExoMars must therefore pursue a holistic search strategy, attacking the problem from multiple angles, including geological and environmental investigations (to characterise potential habitats), visible examination of samples (morphology) and spectrochemical composition analyses. In 1976, the twin Viking landers conducted the first in situ measurements focusing on the detection of organic compounds and life on Mars. Their biology package contained three experiments, all looking for signs of metabolism in soil samples. One, the labelled-release experiment, produced provocative results. If other information had not been also available, these data could have been interpreted as proof of biological activity. However, theoretical modelling of the atmosphere and regolith chemistry hinted at powerful oxidants that could more-or-less account for the results of the three experiments. The biggest blow was the failure of the Viking gas chromatograph mass spectrometer (GCMS) to find evidence of organic molecules at the parts-per-billion level. With few exceptions, the majority of the scientific community has concluded that the Viking results do not demonstrate the presence of life. Numerous attempts have been made in the laboratory to simulate the Viking reactions. While some have reproduced certain aspects, none has succeeded entirely. Incredibly, 30 years after Viking, the crucial chemical oxidant hypothesis remains untested. ExoMars will include a powerful instrument to study oxidants and their relation to organics distribution on Mars. Undoubtedly, the present environment on Mars is exceedingly harsh for the widespread proliferation of surface life: it is simply too cold and dry, not to mention the large doses of UV. Notwithstanding www.esa.int

ExoMars

Recommended Pasteur Exobiology Instruments1 Panorami c Instruments

To characterise the Rover’s geological context (surface and subsurface). Typical scales span from panoramic to 10 m, with a resolution of the order of 1 cm for close targets.

Panoramic Camera System

2 wide-angle stereo cameras and 1 high-resolution camera; to characterise the Rover’s environment and its geology. Also very important for target selection.

Infrared (IR) Spectrometer

For the remote identification of water-related minerals, and for target selection.

Ground Penetrating) Radar (GPR)

To establish the subsurface soil stratigraphy down to 3 m depth, and to help plan the drilling strategy.

C ont ac t Instruments

To investigate exposed bedrock, surface rocks and soils. Among the scientific interests at this scale are: macroscopic textures, structures and layering; and bulk mineralogical and elemental characterisation. This information will be fundamental to collect samples for more detailed analysis. The preferred solution is to deploy the contact instruments using an arm-and-paw arrangement, as in Beagle-2. Alternatively, in case of mass limitations, they could be accommodated at the base of the subsurface drill.

Close-Up Imager

To study rock targets visually at close range (cm) with sub-mm resolution.

Mössbauer Spectrometer

To study the mineralogy of Fe-bearing rocks and soils.

Raman-LIBS2

To determine the geochemistry/organic content and atomic composition of observed minerals. These optical are external heads connected to the instruments inside the analytical laboratory.

external

heads Su pp ort Instruments

These instruments are devoted to the acquisition and preparation of samples for detailed investigations in the analytical laboratory. They must follow specific acquisition and preparation protocols to guarantee the optimal survival of any organic molecules in the samples. The mission’s ability to break new scientific ground, particularly for signs-of-life investigations, depends on these two instruments.

Subsurface Drill

Capable of obtaining samples from 0 m to 2 m depths, where organic molecules might be well-preserved. It also integrates temperature sensors and an IR spectrometer for borehole mineralogy studies.

Sample Preparation and Distribution System (SPDS)

Receives a sample from the drill system, prepares it for scientific analysis, and presents it to all analytical laboratory instruments. A very important function is to produce particulate material while preserving the organic and water content.

Analytical L a bor at or y

To conduct a detailed analysis of each sample. The first step is a visual and spectroscopic inspection. If the sample is deemed interesting, it is ground up and the resulting particulate material is used to search for organic molecules and to perform more accurate mineralogical investigations.

Microscope IR

To examine the collected samples to characterise their structure and composition at grain-size level. These measurements will also be used to select sample locations for further detailed analyses by the Raman-LIBS spectrometers.

Raman-LIBS

To determine the geochemistry/organic content and elemental composition of minerals in the collected samples.

X-ray Diffractometer (XRD)

To determine the true mineralogical composition of a sample’s crystalline phases.

Urey (Mars Organics and Oxidants Detector)

Mars Organics Detector (MOD): extremely high-sensitivity detector (ppt) to search for amino acids, nucleotide bases and PAHs in the collected samples. Can also function as front-end to the GCMS. Mars Oxidants Instrument (MOI): determines the chemical reactivity of oxidants and free radicals in the soil and atmosphere.

GCMS

Gas chromatograph mass spectrometer to conduct a broad-range, very-high sensitivity search for organic molecules in the collected samples; also for atmospheric analyses.

Life-Marker Chip

Antibody-based instrument with very high specificity to detect present life reliably.

1Mass

(without drill and SPDS): 12.5 kg. 2LIBS: Laser-Induced Breakdown Spectroscopy.

Recommended Pasteur Environment Instruments3 Environment Instruments

To characterise possible hazards to future human missions and to increase our knowledge of the Martian environment.

Dust Suite

Determines the dust grain size distribution and deposition rate. It also measures water vapour with high precision.

UV Spectrometer

Measures the UV radiation spectrum.

Ionising Radiation

Measures the ionising radiation dose reaching the surface from cosmic rays and solar particle events.

Meteorological Package

Measures pressure, temperature, wind speed and direction, and sound.

3Mass:

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1.9 kg. The Pasteur environment instruments are presently planned to be accommodated in the GEP.

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The ExoMars surface science exploration scenario. The Rover will conduct measurements of multiple scales, starting with a panoramic assessment of the geological environment, progressing to more detailed investigations on surface rocks using a suite of contact instruments, and culminating with the collection of well-selected samples to be analysed in its laboratory

these hazards, basic organisms could still flourish in protected places: deep underground, at shallow depths in especially benign environments, or within rock cracks and inclusions. The strategy to find traces of past biological activity rests on the assumption that any surviving signatures of interest will be preserved in the geological record, in the form of buried/encased remains, organic material and microfossils. Similarly, because current surface conditions are hostile to most known organisms, as when looking for signs of extant life, the search methodology should focus on investigations in protected niches: underground, in permafrost or within surface rocks. This means that there is a good possibility that the same sampling device and instrumentation may adequately serve both types of studies. The biggest difference is due to location requirements. In one case, the interest lies in areas occupied by ancient bodies of water over many thousands of years. In the other, the emphasis is on water-rich environments close to the surface and accessible to our sensors today. For the latter, the presence of permafrost alone may not be enough. Permafrost in combination with a sustained heat source, probably of volcanic or hydrothermal origin, may be necessary. Such warm oases can only be identified by an orbital survey of the planet. In the next

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few years, a number of remote-sensing satellites, like ESA’s Mars Express and NASA’s Mars Reconnaissance Orbiter (MRO), will determine the water/ice boundary across Mars and may help to discover such warm spots. If they do exist, they would be prime targets for missions like ExoMars. On Earth, microbial life quickly became a global phenomenon. If the same explosive process occurred on the young Mars, the chances of finding evidence of it are good. Even more interesting would be the discovery and study of life forms that have successfully adapted to the modern Mars. However, this presupposes the prior identification of geologically suitable, lifefriendly locations where it can be demonstrated that liquid water still exists, at least episodically throughout the year. For these reasons, the ‘Red Book’ science team advised ESA to focus on the detection of extinct life, but to build enough flexibility into the mission to be able to target sites with the potential for present life.

Mission Description The baseline mission scenario consists of a spacecraft composite with a Carrier and a Descent Module, launched by a Soyuz-2b from Kourou. It will follow a 2-year ‘delayed trajectory’ in order to reach Mars after the dust-storm season. The Descent Module will be released from

the hyperbolic arrival path, and land using either bouncing (non-vented, as in NASA’s rovers) or non-bouncing (vented) airbags, and deploy the Rover and GEP. In the baseline mission, data-relay for the Rover will be provided by a NASA orbiter. An alternative configuration, based on an Ariane-5 ECA launcher, may be implemented depending on programme, technical and financial considerations. In this option, the Carrier is replaced with an Orbiter that provides end-to-end data relay for the surface elements. The Orbiter will also carry a science payload to complement the results from the Rover and GEP, and provide continuity to the great scientific discoveries flowing from Mars Express. ExoMars is a search-for-life mission targeting regions with high life potential. It has therefore been classified as Planetary Protection category IVc. This, coupled with the mission’s ambitious scientific goals, imposes challenging sterilisation and organic cleanliness requirements.

The ExoMars Rover The Rover will have a nominal lifetime of 180 sols (about 6 months). This period provides a regional mobility of several kilometres, relying on solar array electrical power. The Pasteur model payload includes panoramic instruments (cameras, ground-penetrating radar and IR spectrometer; contact instruments for studying surface rocks (close-up imager and Mössbauer spectrometer), a subsurface drill to reach depths of 2 m and to collect specimens from exposed bedrock, a sample preparation and distribution unit, and the analytical laboratory. The latter includes a microscope, an oxidation sensor and a variety of www.esa.int

ExoMars

The Pasteur payload’s drill-bit design concept. The drill’s full 2 m extension is achieved by assembling four sections (one drill tool rod, with an internal shutter and sample-collection capability, plus three extension rods). The drill will also be equipped with an IR spectrometer for mineralogy studies inside the borehole. (Galileo Avionica)

The analysis sequence within Pasteur’s analytical laboratory

instruments for characterising the organic substances and geochemistry in the collected samples. A key element is the drill. The reason for the 2 m requirement is the need to obtain pristine sample material for analysis. Whereas the estimated extinction horizon for oxidants in the subsurface is several centimetres, damaging ionising radiation can penetrate to depths of around 1 m. Additionally, it is unlikely that loose dust may hold interesting biosignatures, because it has been moved around by wind and processed by UV radiation. In the end, organic substances may best be preserved within low-porosity material. Hence, the ExoMars drill must be able to penetrate and obtain samples from well-consolidated (hard) formations, such as sedimentary rocks and evaporitic deposits. Additionally, it must monitor and control torque, thrust, penetration depth and temperature at the drill bit. Grain-to-grain friction in a rotary drill can generate a heat wave in the sample,

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destroying the organic molecules that ExoMars seeks to detect. The drill must therefore have a variable cutting protocol, to dissipate heat in a science-safe manner. Finally, the drill’s IR spectrometer will conduct mineralogy studies inside the borehole.

Conclusion NASA’s highly successful 2004 rovers were conceived as robotic geologists. They have demonstrated the past existence of long-lasting, wet environments on Mars. Their results have persuaded the scientific community that mobility is a must-have requirement for all future surface missions. Recent results from Mars Express have revealed multiple, ancient deposits containing clay minerals that form only in the presence of liquid water. This reinforces the hypothesis that ancient Mars may have been wetter, and possibly warmer, than it is today. NASA’s 2009 Mars Science Laboratory will study surface geology and organics, with the

goal of identifying habitable environments. ExoMars is the next logical step. It will have instruments to investigate whether life ever arose on the Red Planet. It will also be the first mission with the mobility to access locations where organic molecules may be wellpreserved, thus allowing, for the first time, investigation of Mars’ third dimension: depth. This alone is a guarantee that the mission will break new scientific ground. Finally, the many technologies developed for this project will allow ESA to prepare for international collaboration on future missions, such as Mars Sample Return. Following the recent accomplishments of Huygens and Mars Express, ExoMars provides Europe with a new challenge, and a new opportunity to demonstrate its capacity to perform world-class planetary science. ExoMars is now in Phase-B1 and is expected to begin Phase-B2 in mid-2007 e and Phase-C/D in early 2008.

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Doctoral Dissertation Research Proposal: Geographic Representations of the Planet Mars, 1867-1907 K. Maria D. Lane Department of Geography, University of Texas Committee: Ian R. Manners (Chair), Diana K. Davis, Steven D. Hoelscher, Kelley A. Crews-Meyer, Roger Hart

Abstract This dissertation research will use archival and interpretive methods to examine geographical representations of the planet Mars produced by Western astronomers and science writers in the late nineteenth century. Specifically, this project will investigate the ways in which the development of cartography and texts portraying Mars between 1867 and 1907 participated in wider ideological discourses concerning science, imperialism and modernity. The working hypothesis is that representations of Mars’ geography not only reflected the social contexts of astronomical societies, sponsored observatories, and the larger Western scientific communities through the use of common textual tropes and cartographic conventions; but that they also served to modify or construct these very contexts. The proposed research will investigate the extent to which historical geographies of Mars challenged or altered dominant discourses of modern Western superiority by representing the planet as a landscape inhabited by beings with superior engineering and organizational skills. This inquiry will be conducted through archival investigation of three specific conflicts in the representation of Mars that marked turning points in the planet’s astronomy: over (1) the nomenclature assigned to its geographical features, (2) the mapping of canals on its surface, and (3) the interpretation of such canals as the work of intelligent beings. Interpretive analysis of archival materials – including astronomers’ original maps, sketches, manuscripts, observation logbooks, correspondence and lectures; popular media coverage of astronomers’ findings; and contemporaneous maps and documents produced for imperial and other purposes – will focus on reconstructing the historical, social and cultural contexts in which astronomers worked, while also establishing the extent to which discourses of Mars’ geography infiltrated other scientific, imperial and popular dialogues during the same time period. Analysis will be guided by the hypothesis stated above, but will remain open to other scientific-cultural explanations for the nature and meaning of what appear today to be rather curious and remarkable geographies of the Martian landscape. By focusing on maps and texts that are relatively unknown to scholars outside the history of astronomy, this research will contribute materially and theoretically to the history of cartography, science studies, historical geography and studies of colonialism.

Introduction and Research Question Despite the growing interest in nineteenth-century geographical representation, no geographer has yet seriously examined the remarkable discourses that emerged during the latter half of the century to represent the geography of worlds beyond Earth. Popular histories of astronomy (e.g. Sheehan 1996; Morton 2002) indicate that astronomers collected extensive geographic data about the nearby planets, usually recording their findings in detailed maps that were strikingly similar in appearance to many of the well-studied imperial maps produced during the same time period. Although much of this astronomical-geographical knowledge compiled during the late nineteenth century has since been revised or discarded on the basis of twentiethcentury remote sensing images, I contend that colonial-era discourses concerning otherworldly geographies had widespread scientific and cultural significance at the time they were created. The representation of Mars as a canal-covered landscape in 1877, for example, not only reverberated throughout the Western world’s scientific communities, but also initiated a storm of public debate and speculation regarding humankind’s isolation in the universe.

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astronomers’ claims that they could see a canal network on the Martian surface induced widespread theoretical acceptance of the “plurality of worlds” (the existence of humanoid life on celestial bodies other than Earth) in both Europe and the United States over nearly four decades (Guthke 1983; Crowe 1986). Despite the clear cultural significance of this episode, it has largely been dismissed by standard teleological approaches in the history of astronomy as a case of scientific error. The proposed research rejects that interpretation, suggesting instead that a detailed investigation of the statements and interactions of individual astronomers, scientists, public officials and even public media between 1867 and 1907 will reveal the Mars “canal craze” to be a significant and complex negotiation of sciences, cultures, and modernities. Specifically, the project will address the following research questions:

1. In what ways did prominent nineteenth-century geographical discourses regarding Mars’ surface features and inhabitants reflect the specific social contexts of astronomical societies, sponsored observatories, and the larger Western scientific communities? 2. How were scientific representations of Mars as an inhabited, irrigated planet contested and, ultimately, widely accepted as true in Europe and the United States? 3. To what extent did geographies of Mars challenge dominant discourses of modern Western superiority by representing the planet as a landscape inhabited by beings with superior engineering and organizational skills? Theoretical Context This project is theoretically informed by several related literatures that form a compelling interdisciplinary intersection: studies of colonialism, the history of cartography, and science studies. The proposed project will draw from recent inquiries in these literatures, contributing materially or theoretically to each. Studies of Colonialism Historically, the late nineteenth-century production of scientific Mars maps coincided with a period of intense European imperialism, during which both science and cartography (especially scientific cartography) were fundamental to the establishment and maintenance of European power in the colonial realms (Anderson 1991; Godlewska 1995; Ryan 1996; Edney 1997). In the last two decades, studies of nineteenth-century imperialism and colonialism have been dominated by post-colonial scholarship that concerns itself with analysis of the ways in which imperial (and, to a lesser extent, indigenous) maps and texts constitute “discourses,” through which knowledge and power have been negotiated and institutionalized in various regions of the world. The foundational post-colonial work, Said’s Orientalism (1978), argued that imperialism depended for its power on discursive strategies and social practices that constructed geographical knowledge about the colonial realm. Specifically, Said analyzed “Orientalist” discourse to show that Western geographic knowledge about the Islamic world has relied on implicit epistemologies that powerfully support Western dominance of Islamic regions and peoples. He claimed that

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Western Orientalists’ creation of an “imaginative geography” to describe the Islamic world is traceable in the repetition of certain tropes and literary conventions, and that the uncritical acceptance and repetition of these tropes and conventions in Orientalist scholarship frequently resulted in an imaginative discourse that bore little relation to the region’s actual geography. According to Said, Orientalist writing should thus be viewed less as a commentary on the Orient itself than as a reflection of the Occident, showing that Europeans establish their identity in opposition to non-Europeanness, establishing themselves always in a superior, hegemonic position. Despite its merits, however, Said’s work has rightly been criticized for presenting an essentialized, totalizing view of Western scholarship. Although Orientalism analyzed individual texts and authors, Said painted them as powerfully constrained within the bounds of Orientalist structure and ignored any resistance or divergence of approaches, thus leaving himself open to damaging criticism that his analysis implicated all Western authors/scholars in the production of imaginative geographies that fueled imperialism (Driver 1992).

Subsequent post-colonial

scholarship has helpfully focused its scope on a wider variety of Orientalist texts, authors, genres and historical situations (see especially Lowe 1991; Pratt 1992), highlighting many cases of discursive resistance to imperial ideologies and activities. The proposed research will contribute to colonial studies not only by analyzing the extent to which selected astronomical imagery and writing served to construct a previously unstudied “imaginative geography” of Mars, but also by assessing the possibility that such representation constituted a challenge to the dominant Orientalism Said identified. Preliminary analysis suggests that nineteenth-century astronomers and popular science writers used common tropes and metaphors to make the planet’s unfamiliar geography conceptually accessible and familiar to scientific colleagues and popular audiences. Through repetition and uncritical citation of each other’s work, it appears that European and American astronomers created a powerful discourse that represented the red planet as an Earthlike, inhabited, engineered, and irrigated landscape. 3

This discourse employed a number of familiar metaphors that were also present in orientalist and colonial texts, including association with the eternal and immutable classical world (Godlewska 1995), the supposed crippling aridity (Saberwal 1997; Grove 1997) and ruined landscape (Grove and Rackham 2001) of the distant realm, and environmental determinism of inhabitants’ physique/intelligence (Hudson 1977). The nineteenth-century imaginative geography of Mars, like those produced by Orientalists to represent the Islamic world, was certainly more reflective of astronomers’ own geographical notions than of the reality of Mars’ surface characteristics. Nonetheless, it seems to have constrained subsequent investigations and compelled certain perspectives of Mars’ geography until at least the 1960s, when photographic imagery taken by remote probes contradicted the view of Mars as an inhabited planet. Interestingly, however, the standard imaginative representations of Mars appear to have departed from or challenged several well-known imperial tropes, including the presentation of the unknown realm as an empty wilderness (Blaut 1993), the effacement of human presence (Pratt 1992) or “creative destruction” of an existing culture to make way for European customs (Godlewska 1995), the presentation of any inhabitants as backward and depraved (Said 1978), and the assumed superiority of European civilization through technology (Godlewska 1995). The imagined Martians of the late nineteenth century were not the animal-like inhabitants that Europeans described after visiting the Orient; they were skilled, noble engineers who managed to irrigate their arid planet with a massive global system of interlinked canals. These cosmic neighbors were hardly inferior to the modern European technologists who had just completed their first major canal (Suez) in 1869. This preliminary analysis raises exciting challenges to Said’s widely-accepted concept of Orientalism, suggesting that the discourse astronomers engaged in to represent the geography of Mars constructed a familiar imaginative Other that was actually superior to modern Europeans. The ways in which conceptual engagement with this Other – through scientific, philosophical,

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and popular discourses – may have deflected, challenged or transformed modernity’s truth claims in the West will serve as the primary inquiry of the proposed research. History of Cartography Recent scholarship in the history of cartography has paralleled and contributed to many of the developments described above in studies of colonialism. Rejecting a common view of the history of cartography as a linear evolution of cartographic styles, conventions and technologies that continually increase the accuracy of observation, calculation and representation in mapmaking, new approaches in the last few decades have begun to question this prevailing narrative’s Eurocentrism, its claims to objective truth, and its linear notions of progress. A number of powerful revisions have instead begun to examine cartography as a cultural practice, fraught with ideological meanings and distortions that undermine its claims to scientific objectivity (Edgerton 1987; Boelhower 1988; Harley 1989).

Following Harley’s (1989)

revolutionary contention that maps should be read as ideological, cultural texts, cartography has generally come to be accepted as a form of discourse, in which knowledge and power are expressed and negotiated. Given cartography’s long association with the exercise of political and military power, Harley suggested that geographers must consider how the particular historical and ideological circumstances of a map’s production, use and consumption reflect and establish such power (Harley 1988).

Accordingly, some of the most productive recent work in the history of

cartography has critically examined map series prepared by colonial-era explorers and administrators, especially examining the ways in which imperial cartographies metaphorically justified colonial activities or erased indigenous peoples from desirable territories (Ryan 1994; Carter 1999; Edney 1997).

These works indicate that even reconnaissance cartographies

representing basic geographic data necessarily carry ideological meaning. The identity and ideological position of the map’s maker, patron, and audience have been shown to fundamentally

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influence the ways in which maps operate to construct or limit geographical knowledge (Helgerson 1988; Ryan 1994; Manners 1997). This literature clearly informs the proposed examination of nineteenth-century Mars maps (and related representations), requiring a critical evaluation of the social contexts of astronomical societies and sponsored observatories in which individual Mars astronomers worked. Additionally, however, I suggest that the proposed research will contribute materially to the history of cartography by bringing to light a series of map, imagery and texts that closely paralleled the well-studied imperial maps of the same era. As argued above, the ways in which Mars representations differed from standard imperial representations of unknown territories should be examined as a potential site of resistance, in which astronomers differentiated themselves from surveyors or geographers and presented a very different view of Western superiority. Although historians of astronomy and popular science biographers have made some use of the collections I intend to visit, I argue that no modern researcher has seriously considered the turn-of-the-century Mars maps as meaningful scientific or cartographic documents. Despite the fact that historians and geographers have extensively examined imperial cartography produced in the same era, the Mars canal maps have largely been disregarded as curiosities. The few historical works to examine the collections that are relevant to this research have either limited their analyses to chronological accounts of observation technology (Sheehan 1996) and the origins of present-day Mars nomenclature (Blunck 1977), or have dealt only briefly with nineteenth-century mapping as a historical backdrop to analysis of the cultural impact of twentieth-century photographic Mars maps (Morton 2002). By focusing on Mars maps, drawings and related items (correspondence, publications, lectures, etc.) that are relatively unknown to critical scholars outside the history of astronomy, this research will provide a material contribution to the history of cartography.

6

Science Studies The investigative framework for this study is informed primarily by recent advances in science studies. Popular constructivist assertions of the 1970s and 1980s (e.g. Collins 1974; Callon 1986) – that scientific knowledge is influenced by a cultural dimension – have been replaced by critical scholarship that has formulated a model of science as culture (Shapin and Schaffer 1985; Biagioli 1993). In re-reading and revising historical accounts that treat science and culture as separate entities, this new approach to science studies suggests that scientific change occurs as a result of complex cultural negotiation. Identifying numerous instances of “translation” and “hybridization” (subversive appropriation) of one culture’s knowledge/power claims by another, recent scholarship rejects Kuhn’s (1970) idea that science proceeds in revolutionary leaps and bounds. Contemporary science studies has engaged concepts developed in cultural studies to explain the nature of scientific practice and its knowledge/power claims. A linguistic- or discourse-based approach to the ways in which science is negotiated and formulated with various cultural practices or political ideologies, however, raises a host of complex new issues for historians of science to contend with. In critiquing the universal view of science, for instance, historians of science must avoid lapsing into relativistic accounts of the linguistic “incommensurability” of cultural worldviews or knowledge claims (Hart 1999). Such relativism problematically asserts an unbridgeable divide between the “West” and its “Others,” lending unfortunate credence to the persistent notion that Westerners have achieved superiority over nonWestern civilizations on the basis of technological superiority (Adas 1989) or unique quantitative perceptions of reality (for a critique of this view, see Hart 2000). Recent cultural studies of science have accordingly developed the concept of “translation” to dismantle monolithic notions of “the West” and its “science,” fundamentally revising traditional historiography of the cultural encounters between Western explorers, merchants, missionaries or colonial administrators and non-Western societies (Prakash 1999; Hart 1999). 7

The research proposed here will examine late nineteenth-century astronomy as a culture, governed both by internal rules and constraints as well as external needs to communicate with other scientific and institutional cultures. Archivally, this research will investigate the particular settings in which individual astronomers worked to produce articles, lectures and, importantly, maps that recorded their observational findings regarding Mars’ geography. Analytically, it will elucidate the intertwining of particular national, institutional, and social contexts with astronomers’ scientific activities. For instance, the proposed research will investigate the ways in which astronomers’ use of modern cartographic conventions may have functioned as an attempt to shore up astronomy’s (and astronomers’) disciplinary status in the face of increasing imperialist hype and funding for natural sciences such as geography. Analysis of the interactions among astronomers of differing nationalities, competing institutions, and varying social groups will focus on the localized contestation and negotiation of particular knowledge claims through both texts and maps. This focus will provide a critical view of the ways in which astronomers positioned themselves and defined their scientific identity through their studies of Mars. In addition, the proposed research will investigate the cultural interactions among Mars astronomer-geographers and other intellectuals in related scientific and philosophical disciplines. Applying a science studies approach, the debated acceptance of certain astronomers’ statements regarding the existence of a canal network on Mars’ surface can be examined as a process of translation and negotiation. Examination of the publications and direct communications between individuals who interpreted the Martian canals as evidence of aliens and those who subscribed to a metaphysical belief that humans were alone in the universe will help determine whether these groups engaged in strategies of subversive appropriation and modification of each other’s claims. If so, the textual and cartographic record of how such claims were translated and negotiated will be probed for evidence of the extent to which the discourse regarding Mars’ canals produced new cultural worldviews.

8

Finally, this research will investigate the particular characteristics of the negotiated view of Mars as a “plural world,” inhabited by humanoid “Others.” Although the late nineteenthcentury discourse regarding Mars’ inhabitants clearly employed notions of difference, familiarity and superiority – elements that Said (Said 1978) identified as central to the modern Western project of knowledge production – numerous astronomers and their allies formulated these concepts differently, postulating that Martians were actually superior to humans. In this sense, I argue, nineteenth-century Mars astronomy may have constituted an alternate modernity, one that in fact interacted significantly with the contemporaneous imperialist modernity. Using a cultural studies approach, this negotiation of modernities will be investigated as a process of cultural translation, discernible in the historical record through publications by and communications among representatives of the various modernities.

Research Plan and Methodology Using methods of historical and archival research, this inquiry will be carried out by examining three specific conflicts in the representation of Mars: (1) the controversy over Mars’ nomenclature, which focuses mainly on the contentious transition from Richard Proctor’s 1867 surname-based scheme to Giovanni Schiaparelli’s 1877 classical Latin convention based on the geography of the ancient Mediterranean world; (2) the vigorous debate over the existence of Martian canals between Schiaparelli and Nathaniel Green, whose 1877 maps differed widely in level of detail; and (3) the conflicts regarding sensationalism during the “Canal Craze” of the 1890s and early 1900s, consisting mainly of attacks on Percival Lowell by skeptical astronomers and other scientists who refuted his interpretations of the Martian canals as the work of intelligent beings. Each of these controversies marked a turning point in Mars astronomy (Sheehan 1996) and thus represents a rich opportunity for detailed analysis of the research questions outlined above.

9

Archival Research To analyze these controversies, I will travel to relevant libraries and observatories (see below) to view astronomers’ original maps, sketches, manuscripts, observation logbooks, correspondence, lectures and other materials in order to reconstruct the specific historical and social contexts that influenced their work. In addition, I will compare representations of Martian geography with the numerous geographical discourses presented in secondary sources that have been interpreted from contemporaneous maps and documents, such as those produced for imperial purposes. Finally, I will review original sources at each repository (and related archives, where necessary) for evidence of the extent to which discourses of Mars’ geography infiltrated other scientific and popular dialogues during the same time period. This will include examination of newspaper articles, popular essays, books and other materials. Repository/Location Lowell Observatory Library Flagstaff, Arizona

Royal Astronomical Society Library London, UK

Brera Observatory Archive Milan, Italy

Collections Percival Lowell collection (1894-1916) • Observation log books • Correspondence • Published manuscripts • Lectures • “Mars craze” clipping file RAS Letters • Richard Proctor correspondence • Other Mars-related correspondence RAS MSS • Nathaniel Green’s Mars maps/drawings 1877-1888 and assorted personal papers RAS Papers • Proctor’s / Green’s publications • Mars maps, various astronomers • Scientific and popular journals • RAS lectures • Mars globes • Cartoons Giovanni Schiaparelli collection • Observation logbooks • Published manuscripts • Mars drawings/maps • Correspondence

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Interpretation and Analysis Interpretive analysis of these archival materials will remain open to various cultural and scientific explanations for the nature and meaning of what appear today to be rather curious and remarkable geographies of the Martian landscape.

The interpretive focus, however, will

primarily investigate the possibility that nineteenth-century Mars astronomy may have significantly challenged dominant discourses of modern Western superiority by representing the planet as a landscape inhabited by beings with superior engineering and organizational skills. In order to assess the validity of this preliminary hypothesis, Said’s methodological approach to discourse analysis will be used to identify narrative voice, literary structures, figures of speech, images, themes, and motifs evident in individual scientific texts. Although Said did not claim that his methods of discourse analysis could be applied to maps or other images, this research will methodologically follow the examples of scholarship in the history of cartography that suggests the identification and interpretation of conventions such as scale, framing, selection and coding (Harley 1988; Cosgrove 1999) can be used to interpret maps as texts. To determine the ways in which tropes and conventions used in individual texts and maps constituted (or did not constitute) a broader discourse, Mars representations will be examined in relation to one another. As Said showed for the Orientalist literary canon, I expect to be able to demonstrate that certain representational conventions became broadly established in the Mars-related scientific literature over time, especially when they metaphorically presented Mars’ geography in familiar (terrestrial) terms. Accepting Said’s (1978) premise (drawn from Foucault) that knowledge reflects and maintains power, this project will seek to interpret the ways in which nineteenth-century representations of Mars, which had widespread scientific and cultural significance at the time they were created, influenced the hegemonic power of the modern Western nations in which such representations were produced and consumed. In this regard, analysis of the Mars discourse will be situated alongside analyses of contemporaneous orientalist discourses, such as Said’s argument 11

that imaginative geography produced the West’s superiority complex, Mitchell’s (1989) argument that Western forms of representation themselves constitute a “method of order and truth”(236), and even Bhabha’s (1995) hypothesis that European modernity was fashioned by its encounter with the colonial Other. In conducting an analysis of the Martian geography discourse, however, this research will carefully avoid the pitfall of treating Western astronomy as if it were a unified endeavor. Although I argue that a dominant discourse emerged to represent Mars, this research will specifically focus on resistance and controversy (regarding the nomenclature applied to surface features, for example) as a way of highlighting the heterogeneity of approaches to the presentation of Mars. Learning from both Said’s mistakes and the helpful corrections provided by subsequent colonial discourse analysts (Lowe 1991; Pratt 1992), this research will analyze the ways in which competing representations of Mars were produced by astronomers working in different professional and cultural settings, writing for different audiences. The resolution of various controversies in favor of certain astronomers’ opinions over others’ will be assumed to reflect a variety of power relationships that can be read through the discourse of the maps and texts.

Preparation to Conduct the Proposed Research In preparation for undertaking this research, I have begun communicating with librarians/curators at repositories that hold the papers and maps of Proctor, Green, Lowell and their contemporaries. In initial contacts, I have verified the extent and accessibility of their collections, and have received enthusiastic support for my dissertation research. Although contact has not yet been established with the Brera Observatory, where Schiaparelli’s papers and maps are held, other researchers familiar with the facility have assured me that it will be accessible and suitable for my research inquiries. Given this initial legwork, I propose that the

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archival research activities outlined above can reasonably be accomplished according to the timeline below. Methodological Preparation As a doctoral student, I have taken methodological coursework in historical/ archival research and discourse/metaphor analysis that uniquely prepares me to undertake a complex research design that will rely on historical interpretation of a number of disparate archival sources. During this time, I have also completed two projects in original discourse analysis, both of which resulted in well-received papers that have allowed me to clarify my understanding of methodological nuances. Language Competency The majority of the documents and maps I intend to examine are in English, as Proctor, Green and Lowell published and corresponded primarily in English. Schiaparelli’s work was published mainly in Italian, however, and some of his correspondence (especially with English and American colleagues) is in French. Accordingly, I have begun study of Italian this semester, with a focus on reading skills, intending to attain the equivalent of second-year Italian by the time I visit the Italian archives. My working knowledge of both Spanish and Portuguese will help me swiftly achieve reading knowledge of Italian before summer 2004. To analyze correspondence written in French, I intend to rely on existing or commissioned translations.

Timeline for Research Activities Phase 1: January – April 2003 (Austin, Texas) • Proposal defense, advancement to doctoral candidacy • Secondary source readings on Percival Lowell and contemporaries • Preparations for archival research at Lowell • Italian language course • Grantwriting Phase 2: May – June 2003 (Flagstaff, Arizona) • Archival research at Lowell Observatory Phase 3: July – December 2003 (Austin, Texas) 13

• • • • • •

Analysis of research findings Followup travel to relevant U.S. repositories, as needed Secondary source readings on Richard Proctor, Nathaniel Green, Giovanni Schiaparelli Preparations for archival research at RAS, Brera Italian language courses (summer B and fall semester) Grantwriting

Phase 4: January – May 2004 (London, UK) • Archival research at Royal Astronomical Society and related English repositories Phase 5: June – August 2004 (Milan, Italy) • Archival research at Brera Observatory and related Italian repositories Phase 6: September 2004 – August 2005 (Austin, Texas) • Analysis of research findings • Dissertation writing • Preparation of articles and conference presentations Potential Funding Sources To fund the archival phases of the proposed research, I applied in Fall 2002 or will apply in Spring 2003 for a number of grants, fellowships, and awards, including: •

Council on Library and Information Resources: Mellon Fellowship for Dissertation Research in Original Sources ($20,000 – 12 months)

•

NASA-American Historical Association: Fellowship in Aerospace History ($20,000 – 12 months)

•

National Science Foundation: Doctoral Dissertation Research Improvement Grant in Science and Technology Studies ($12,000 – 9 months)

•

University of Texas Department of Geography: Teaching Assistantship ($11,900 – 9 months)

•

Society of Women Geographers: Evelyn L. Pruitt National Fellowships for Dissertation Research ($15,000 – 12 months)

•

Royal Astronomical Society: Grants for Studies in Astronomy and Geophysics (£5,000)

•

J.B. Harley Research Fellowships in the History of Cartography (£1,000 – 4 weeks)

In addition, I intend to apply in Fall 2003 for awards that would fund dissertation writing after the archival phases of the research are complete, including: •

American Association of University Women: American Fellowships for Dissertation Research ($20,000 – 12 months)

•

University of Texas: Harrington Dissertation Fellowship ($25,000 – 12 months)

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Works Cited Adas, Michael. 1989. Machines as the measure of man: science, technology, and ideologies of Western dominance. Ithaca and London: Cornell University Press. Anderson, Benedict. 1991. Imagined communities. 2nd ed. New York: Verso. Bhabha, Homi K. 1995. Cultural diversity and cultural differences. The post-colonial studies reader. Editors Bill Ashcroft, Gareth Griffiths, and Helen Tiffin, 206-9. London: Routledge. Biagioli, Mario. 1993. Galileo, courtier: the practice of science in the culture of absolutism. Chicago: University of Chicago Press. Blaut, J. M. 1993. The colonizer's model of the world: geographical diffusionism and Eurocentric history. New York : Guilford Press. Blunck, Jurgen. 1977. Mars and its satellites: a detailed commentary on the nomenclature. Hicksville, New York: Exposition Press. Boelhower, William. 1988. Inventing America: a model of cartographic semiosis. Word and Image 4, no. 2: 475-97. Callon, Michel. 1986 [1999]. Some elements of a sociology of translation: domestication of the scallops and the fishermen of St. Brieuc Bay. The science studies reader. Editor Mario Biagioli, 67-83. New York: Routledge. Carter, Paul. 1999. Dark with excess of bright: mapping the coastlines of knowledge. Mappings. Editor Denis Cosgrove, 125-47. London: Reaktion Books. Collins, H. M. 1974 [1999]. The TEA set: tacit knowledge and scientific networks. The science studies reader. Editor Mario Biagioli, 95-109. New York: Routledge. Cosgrove, Denis. 1999. Introduction: mapping meaning. Mappings. Editor Denis Cosgrove, 123. London: Reaktion Books. Crowe, Michael J. 1986. The extraterrestrial life debate 1750-1900: the idea of a plurality of worlds from Kant to Lowell. Cambridge: Cambridge University Press. Driver, Felix. 1992. Geography's empire: histories of geographical knowledge. Environment and Planning D: Society and Space 10: 23-40. Edgerton, Samuel Y. 1987. From mental matrix to mappamundi to Christian empire: the heritage of ptolemaic cartography in the Renaissance. Art and Cartography. Editor David Woodward, 10-50. Chicago: University of Chicago Press. Edney, Matthew H. 1997. Mapping an empire: the geographical construction of British India, 1765-1843. Chicago and London: The University of Chicago Press.

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Godlewska, Anne. 1995. Map, text and image: The mentality of enlightened conquerors: a new look at the Description de l'Egypte. Transactions of the Institute of British Geographers 20: 5-28. Grove, A. T., and Oliver Rackham. 2001. The nature of Mediterranean Europe: an ecological history. New Haven: Yale University Press. Grove, Richard H. 1997. Ecology, climate and empire. White Horse Press. Guthke, Karl S. 1983. The last frontier: imagining other worlds, from the Copernican revolution to modern science fiction. Translator Helen Atkins. Ithaca and London: Cornell University Press. Harley, J. B. 1988. Maps, knowledge, and power. The iconography of landscape: essays on the symbolic representation, design and use of past environments. Editors Denis Cosgrove, and Stephen Daniels, 277-312. Cambridge: Cambridge University Press. ———. 1989. Deconstructing the map. Cartographica 26: 1-20. Hart, Roger. 1999. Translating the untranslatable: from copula to incommensurable worlds. Tokens of exchange: the problem of translation in global circulations. Editor Lydia H. Liu, 45-73. Durham and London: Duke University Press. ———. 2000. The great explanadum, review of Alfred W. Crosby's The Measure of Reality: Quantification and Western Society 1250-1600. American Historical Review 105, no. 2: 486-93. Helgerson, Richard. 1988. The land speaks: cartography, chorography, and subversion in Renaissance England. Representing the English Renaissance. Editor Stephen Greenblatt, 327-61. Berkeley: University of California Press. Hudson, Brian. 1977. The new geography and the new imperialism: 1870-1918. Antipode 9, no. 2: 12-19. Kuhn, Thomas S. 1970. The structure of scientific revolutions. 2nd ed., Vol. 2. International Encyclopedia of Unified Science, eds. Otto Neurath, Rudolf Carnap, and Charles Morris, 2. Chicago: University of Chicago Press. Lowe, Lisa. 1991. Critical terrains: French and British orientalisms. Ithaca, NY : Cornell University Press. Manners, Ian. 1997. Constructing the image of a city: the representation of Constantinople in Christopher Buondelmonti's Liber Insularum Archipelagi. Annals of the Association of American Geographers 87, no. 1: 72-102. Mitchell, Timothy. 1989. The world as exhibition. Comparative Studies in Society and History 31: 217-36. Morton, Oliver. 2002. Mapping Mars: science, imagination and the birth of a world. London: Fourth Estate.

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Prakash, Gyan. 1999. Another reason: science and the imagination of modern India. Princeton, New Jersey: Princeton University Press. Pratt, Mary Louise. 1992. Imperial eyes: travel writing and transculturation. London: Routledge. Ryan, Simon. 1994. Inscribing the emptiness: cartography, exploration and the construction of Australia. De-scribing empire: post-colonialism and textuality. Editors Chris Tiffin, and Alan Lawson, 115-30. London: Routledge. ———. 1996. The cartographic eye: how explorers saw Australia. Cambridge: Cambridge University Press. Saberwal, Vasant K. 1997. Science and the desiccationist discourse of the 20th century. Environment and History 3: 309-43. Said, Edward W. 1978. Orientalism. New York: Pantheon Books. Shapin, Steven, and Simon Schaffer. 1985. Leviathan and the air-pump: Hobbes, Boyle and the experimental life. Princeton: Princeton University Press. Sheehan, William. 1996. The planet Mars: a history of observation and discovery. Tucson: The University of Arizona Press.

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Lunar and Planetary Science XXVIII

JSC MARS-1: MARTIAN REGOLITH SIMULANT Carlton C. Allen1, Richard V. Morris2, David J. Lindstrom2, Marilyn M. Lindstrom, and John P. Lockwood3 1Lockheed Martin Engineering & Sciences, Houston, TX 77058 2NASA Johnson Space Center, Houston, TX 77058 3Hawaiian Volcano Observatory, Hawaii Volcanoes NP, HI 96718 We have developed a simulant to the regolith of Mars for support of scientific research, engineering studies, and education. JSC Mars-1 is the <1 mm size fraction of a palagonitic tephra (glassy volcanic ash altered at low temperatures). The material was collected from the Pu’u Nene cinder cone, located in the saddle between Mauna Loa and Mauna Kea volcanoes on the Island of Hawaii. Palagonitic tephra from this cone has been repeatedly cited as a close spectral analog to the bright regions of Mars [1,2,3]. Simulant Preparation and Analysis. The tephra was mined from a cinder quarry on the slope of Pu’u Nene cone. Soil overburden was removed and tephra was collected from a palagonitized zone 4060 cm thick. The tephra was dried and sieved to separate the <1 mm size fraction. This material was packaged in moisture-proof containers for shipping and storage. Preliminary Simulant Characterization. We analyzed a single sample from the area chosen for large scale simulant preparation. Splits were characterized by visible and near-IR (VIS/NIR) reflectance spectroscopy at the Johnson Space Center. X ray fluorescence (XRF) and loss on ignition (LOI) analyses were performed at Washington State University. We intend to publish detailed data from representative samples of JSC Mars-1 in the near future. Spectra. JSC Mars-1 is yellow-brown in color. Figure 1 compares the VIS/NIR spectrum of the simulant to a composite martian bright region spectrum (atmospheric contributions removed) [4]. Both spectra contain a relatively featureless ferric absorption edge through the visible, an indication of a ferric absorption band in the 800-900 region, and relatively flat absorption in the near-IR. Bands at 1400 and 1900 nm in the simulant spectrum result from higher levels of H2O and OH in the simulant than on Mars. The presence of the ferric features near 600, 750 and 860 nm in the martian spectrum imply higher levels of red (well-crystalline and pigmentary) hematite on Mars than in the simulant [5,6]. Chemical Composition. Table 1 lists the major and minor oxide composition of JSC Mars-1, as measured by XRF. This composition is compared to that of a typical Mars surface sample analyzed at the Viking lander 1 (VL-1) site [7]. Mineralogy. Morris et al. [3] published extensive analyses of a <1 mm tephra sample collected from Pu’u Nene. The sample is dominated by amorphous palagonite. The only phases detected by X ray diffraction are plagioclase feldspar and minor magnetite. These analyses constrained the abundance of phyllosilicates to <1 wt.%. Iron Mossbauer spectroscopy detected magnetite as well as traces of hematite, olivine, pyroxene and/or glass. The majority of iron was present as nano-phase ferric oxide (64%). These data yield a Fe2+/Fe3+ ratio of 1/3. Grain Size. Table 2 lists the published grain size distribution of Pu’u Nene tephra [3]. For comparison, the blocky material which covers 78% of the area near VL-1 on Mars ranges in size from 0.1-1500 m [8]. Specific Gravity. The bulk specific gravity of JSC Mars-1 is 0.8 g/cm3. This value can be increased to 0.9 g/cm3 by vibrating the sample. The drift material near VL-1 has a specific gravity of 1.2 +/- 0.2 g/cm3 and the blocky material has a value of 1.6 +/- 0.4 g/cm3 [8]. Magnetic Properties. JSC Mars-1 contains a highly magnetic component. Approximately 25 wt.% of the sample can be lifted with a strong magnet. By comparison, observations of the Viking sample arm magnets indicate that the martian soil contains between 1-7% magnetic material [9]. Availability. We anticipate that approximately 9,100 kg (20,000 lb) of JSC Mars-1 will be available in 1997 for distribution to qualified investigators and teachers. The simulant will be stored at the Johnson Space Center. Anyone desiring a portion of this material should address their request to Dr. Carlton Allen (address above; telephone 281-483-2630, fax 281-483-5347). References. [1] Evans, D. L. and Adams, J. B. (1979) Proc. 10th Lunar Planet. Sci. Conf. 1829-1834. [2] Singer, R. B. (1982) J. Geophys. Res. 87, 10,159-10,168. [3] Morris, R. V. et al. (1993) Geochim. Cosmochim. Acta 57, 4597-4609. [4] Mustard, J. F. and Bell, J. F., III (1994) Geophys. Res. Lett. 21, 3353-3356. [5] Morris, R. V. and Lauer, H. V., Jr. (1990) J. Geophys. Res. 95, 5101-5109. [6] Morris, R. V. et al. (1997) J. Geophys. Res. in press. [7] Clark, B. C. et al. (1982) J. Geophys. Res. 87, 10,059-

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JSC MARS-1: MARTIAN REGOLITH SIMULANT: Allen, C.C. et al.

10,067. [8] Moore, H. J. et al., (1987) U.S.G.S. Prof. Paper 1389. [9] Hargraves, R. B. et al., (1977) J. Geophys. Res. 82, 4547-4558.

Figure 1. VIS/NIR reflectivity spectra of Mars Composite Bright Region [4] and JSC Mars-1 Table 1.

Table 1. (continued)

Chemical Composition

JSC Mars-1

Oxide SiO2 Al2O3 TiO2 FeO Fe2O3 MnO CaO MgO K2O Na2O P2O5 SO3 Cl

Wt.%* 34.5 18.5 3.0 2.8 9.3 0.2 4.9 2.7 0.5 1.9 0.7 n.a. n.a.

LOI****

21.8

Wt.%** 43.7 23.4 3.8 3.5 11.8 0.3 6.2 3.4 0.6 2.4 0.9 n.a. n.a.

Martian Surface Fines C-1 Wt.%*** 43 7.5 0.65 n.d. 17.6 n.a. 6 6 0 n.a. n.a. 7 0.7

n.d. not detected n.a. not analyzed Fe2+/Fe3+ = 1/3 * XRF ** XRF normalized without LOI *** Ref [7] **** Weight loss after heating for 2 hrs in air at 900 C (includes H2O, SO3 , Cl)

Table 2.

Pu’u Nene Tephra Grain Size* Size ( m)

500-1000 250-500 150-250 90-150 45-90 20-45 <20 * Ref [3]

Wt.% 21.4 29.5 20.8 12.9 9.2 5.4 1.3

Mars Exploration "Follow the Water" Young Ho Park Jet Propulsion Laboratory Pasadena, CA 91109 Abstract— The red planet Mars has been a subject of imagination over the centuries, as well as intense scientific interest. As the overwhelming success of two Mars Exploration Rovers unfold before us, this article reviews the overview of NASA's Mars Exploration and rationale. 1. INTRODUCTION In 2004, we have observed two historic events in Mars exploration. The first Mars Exploration Rover (named Spirit) landed on Mars on January 3, 2004. The second Mars Exploration Rover (named Opportunity) landed on Mars on January 24, 2004. At the time of this writing, both rovers are operating nicely, taking pictures of Mars surface and taking various scientific measurements to reveal many secrets of Mars now and many, many years ago. There have been only five successful landing of spacecraft on Mars surface: Viking 1 Lander 1 and 2 in 1975, Mars Pathfinder with Sojourner in 1997 and Spirit and Opportunity this year. As we know that many Mars missions have failed, Mars missions are challenging and require extreme ingenuity and dedication of all involved team. 2. MARS VS EARTH Mars is the fourth planet from Sun. The distance from Sun is about 1.5 times that of Earth. The mass of Mars is 10% of Earth. The diameter of Mars is 53% of Earth. The gravity of Mars is 37% of Earth. The Mars atmospheric pressure is only 0.7% of Earth atmosphere. The average recorded temperature on Mars is -63° C with a maximum temperature of 20° C and a minimum of 140° C. The atmosphere of Mars is quite different from that of Earth. It is composed primarily of carbon dioxide with small amounts of other gases. The six most common components of the atmosphere are: Carbon Dioxide (95.3%), Nitrogen (2.7%), Argon (1.6%), Oxygen (0.13%), Water (0.03%), Neon (0.00025 %).

Figure 1. Earth and Mars 3. WHY MARS? Mars is the only planet, other than Earth, that shows strong evidence of liquid water having coursed over its surface. There are many clear signs of rivers and lakes on Mars surface (Figure 2). Based on limited Mars exploration, it seems that there is no obvious sign of water on Mars surface at this time. However, there is abundance of indication that once water flowed on Mars surface at one time or another in the long history of Mars. Although our current understanding of life's origins may be limited, at least on Earth, there is life where water is. Thus, based on we see on Mars surface it is possible that Mars may have been habitable and may have harbored life. In Figure 3, striking features of gullies are shown in the picture recently taken by Mars Orbiter Camera on Mars Global Surveyor. According to a dictionary, a gully is "a deep ditch or channel cut in the earth by running water after a prolonged downpour". No one is sure yet how the gullies are formed. One conjecture is that subsurface water or ice melted and the water may have gushed out. The implication of this conjecture is tremendous so that there may be water or ice under the Martian surface even at present time. An analogy may be permafrost on Earth in polar region such as Alaska. The permafrost is permanently frozen subsurface soil. However, caution may be required to draw such haste conclusion without further conclusive evidence.

NASA has created Mars Program with a theme of " Follow the Water." The objective of the program is to detect conclusive evidence whether water existed on Mars, water exists on Mars subsurface if not on surface, and ultimately evidence whether life, even in microbiological life form, existed in the lifetime of Mars.

Figure 4. Artist Conception of a Mars Exploration Rover. Figure 2. Mars Surface picture taken by a Mars Orbiter

Mars Exploration Rover A (now called Spirit) was launched on June 10, 2003 and landed on Mars on January 3, 2004. Mars Exploration Rover B (now called Opportunity) was launched on July 7, 2003 and landed on Mars on January 24, 2004. Both rovers are identical in design. The names of rovers were suggested by a schoolgirl and selected after a worldwide competition. As seen in media, both rovers are conducting their scientific mission among many challenges. Each rover has 90 Martian days for it's prime mission. Scientific instruments of each rovers are: Panoramic Camera, MiniThermal Emission Spectrometer, Microscopic Imager, Moessbauer Spectrometer, Alpha Particle X-Ray Spectrometer. The robotic arm includes rock abrasion tool. Also, each rover has magnet arrays. (For more information visit http://marsrovers.jpl.nasa.gov/) MER Spirit has landed in Gusev crater area (Figure 5) and the current Mars surface does not seem to have liquid water. However, the scientists believe that Gusev crater area included flowing water, accumulated water in lakes, and deposit of sediment over a long period of time. This history makes Gusev crater very interesting exploration site. Figure 6 shows the picture where MER Spirit examines a Mars Rock.

Figure 3. Picture taken by Mars Orbiter Camera on Mars Global Surveyor 4. MARS EXPLORATION ROVER Mars Explorer Rover (MER) mission is to send two rovers to Mars. The scientific objective is to determine the history of climate and water at sites on Mars where conditions may once have been favorable to life. Each rover is equipped with a suite of science instruments that will be used to read the geological record at each site, to investigate what role water played there, and to determine how suitable the conditions would have been for life.

MER Opportunity has landed in a small crater in Meridiani Planum (Figure 5). Meridiani Planum interests scientists because it contains an ancient layer of hematite, an iron oxide that, on Earth, almost always forms in an environment containing liquid water. The site appears dry now. So how did the hematite get there? Was there once water in the area? If so, where did it go? These are main questions for which MER Opportunity will collect in-situ measurement data.

Figure 5. Landing Site for Mars Exploration Rovers

Figure 6. MER Spirit examining a Mars Rock 5. FUTURE AND SUMMARY In addition to two Mars rovers on Martian surface, NASA has two spacecraft orbiting Mars now: Mars Global Surveyor and Mars Odyssey. Also, European Space Agency has Mars Express in Mars Orbit currently. NASA plans to send one spacecraft to Mars every two years. Phoenix (a lander) will be launched in 2007 and Mars Science Laboratory (MSL, a rover) will be launched in 2009. In a long term, a Mars sample return mission is considered.

Figure 7. Layered Rock picture taken by MER Opportunity Of course, President has set a long-term goal for sending men to Mars possibly within two decades. People ask, " Why do we do this for such a high cost?" Practical answer is that there are invaluable science and technological byproduct. Teaching science and technology and inspiring next generation are another essential part. On the other hand, continuous advancement of a civilization is only possible with the spirit of "Exploration".

14307

Radar Ranging of the Planet Mars at 8495 MHz G. S. Downs and P. E. Reichley Communications Systems Research Section

A simulation was performed for the radar system in order to ensure detection of the planet Mars at the start of the 1975 series of radar probes of the surface. Appropriate parameters were found. Appropriate parameters were also found for use at opposition (December 1975). Systematic errors in the measured delay with changes in surface roughness were observed. This effect is shown to be many times larger than the expected rms fluctuations in the measured delays.

from the surface of the planet was determined. Up to 120 delay measurements were made to allow determination The surface of the planet Mars will be probed with of the detection probability and the measurement accuS- and X-band radar signals during 1975 and 1976, all in racy. An appropriate set of radar parameters was chosen preparation for the landing of two spacecraft in 1976. in light of the results of this study. The measurements to be performed at JPL will use the R & D radar system at DSS 14, Goldstone, California, at a frequency of 8495 MHz. In preparation, several series II. How Delay Is Measured of radar data sets were simulated and processed. That is, The basic radar data set consists of a matrix of rethe expected power in the reflected signal was calculated ceived power as a function of time delay and excess dopas a function of time delay and frequency for several sets pler shift. Separate regions on the surface will exhibit of radar system parameters. The random fluctuations separate time delays because of the spherical shape of caused by receiver noise were superimposed using a the planet. random number generator. The appropriate signal-tonoise ratio was calculated for certain distances to the planet, assuming appropriate X-band antenna paramLet 9 represent the angle between the line of sight from eters. The round-trip time delay of the signal reflected the radar to the center of the planet and the radius to the \. Introduction

JPL DEEP SPACE NETWORK PROGRESS REPORT 42-29

95

point on the surface. The time delay ^ of the signal reflected from that surface point back to the radar is given by (1)

where R is the radius of the planet and c is the speed of light; D is the distance along the line of sight to the closest point on the surface. Note that 6 is also the angle of incidence of the signal on the surface. 6 and D are each functions of time. The large delay due to D is removed at the time of data collection. The small changes in 6 due to the relative motion of Mars and Earth in the time interval 2D/c are neglected. The locus of a curve of a constant r is a circle in the plane perpendicular to the line of sight and whose center lies on the line of sight. Regions of a particular delay are isolated by modulating the phase of the transmitted signal with a pseudorandom binary code. If the bit length of the code is T seconds, the normalized cross correlation function of the transmitted signal with the received signal is given by - -^ IT - T« I; RrM

-T 0 |


(2)

'• -TO!

>T

where TO is the round trip delay. A band of surface elements located within T seconds of TO can be isolated. In practice, the received signal is passed through a bank of correlators, the tth corresponding to a round trip delay T 0 j. The power in the output of the ith correlator is then the sum of the power in the reflected signals corresponding to the delays r0i — T
circles of constant range and the circles of constant doppler shift then isolate particular small regions on the surface (see Fig. 1). Therefore, the discrete power spectrum of the output of each correlator is estimated using discrete time samples. The power at each discrete frequency fa in the spectrum is in fact the sum of power from regions of varying doppler shift /. Each region is weighted by the familiar function (3)

where N is the number of discrete frequencies, separated by A/, in the power spectrum. The delay-doppler geometry imposed on the planet's surface is pictured in Fig. 1, where the planet is viewed from the direction of the apparent spin axis. The angle of incidence 6 is the angle between the direction to Earth and IV, the local normal to the mean sphere. The shape of the range window R(T) is shown at the left for the case of T = 6 /iS. The shape of the doppler window D(/) is shown at the right for the case of A/ = 10.2 Hz, when A. = 12.55 cm. As is often the case in these measurements, the correlators are separated such that TOU + D — roi = T/2. Note that as the planet rotates, any given region near the doppler equator (a great circle perpendicular to the circles of constant doppler shift and bisecting the rings of constant range) is probed at a variety of angles of incidence. Each set of received power as a function of delay and doppler (a data frame) represents a snapshot of the surface near the doppler equator. An example of such a data frame appears in Fig. 2. Consider for the moment the power vs time delay at a fixed doppler shift. The reflected power corresponds to a narrow region at a particular longitude and a minimum angle of incidence. The location of the planet at that particular doppler shift is taken to be the delay at which the power is a maximum. As the planet rotates, a series of delay functions corresponding to particular values of 6 become available for a particular longitude. With the extra delay due to curvature of the surface removed, the collection of delay functions is usually added to produce a composite delay function in which the signal-to-noise ratio is larger. The delay corresponding to the peak power then defines the distance to the planet. In practice, the presence of noise will cause errors in locating the planet. Also, the weak signal case gives rise to a finite possibility of a false detection of the planet. JPL DEEP SPACE NETWORK PROGRESS REPORT 42-29

The following discussion is devoted to a determination of the probability of a correct detection and the measurement error, once detection has been established. These probabilities and errors are dependent on the signal-tonoise ratio, which in turn is dependent on the parameters of the radar system and the surface characteristics. The radar system parameters and surface characteristics are varied over an appropriate range in the discussion below.

III.

The Data

An example of simulated data is presented in Fig. 2. The spectrum of the output of 32 correlators is presented in Fig. 2(a) for the noise-free case. The magnitudes of the spectral components are proportional to the received power expected for the case of T — 6 /*s and A/ = 36.2 Hz at A = 3.53 cm. Note that correlators are offset progressively in delay by T/2 = 3 ps. These magnitudes were calculated by evaluating the radar equation: P,GJ.GrA2

p0C

//

ds.

R(r - r0) D(f -

(4)

where P, and G, are the transmitting power and antenna gain, respectively. G, is the receiving antenna gain. The transmitter operates at wavelength A. The planet, located at distance D, is characterized by a reflectivity p0 and roughness parameter C. The denominator of the integrand in Eq. (4) (sometimes called the Hagfors backscatter function, Refs. 1 and 2) describes how the power scattered back toward the receiver varies with the angle of incidence, where 0 is now a function ^ and /. The surface S over which the integration takes place is determined by the position of the range and doppler windows relative to the planet. The details of the evaluation of the integral, and in particular the effects of aliasing in frequency and ambiguity in range will be discussed in a forthcoming article. The received power P(f,r) was calculated for 32 delays and 64 frequencies for values of A/ = 36.2, 72.5 and 145 Hz with T = 6 us and for A/ = 1'45 Hz with T = 12 ^s. In each case, T O ( ^ I I — T0i = AT — T/2. In the case of Mars, these values of A/ correspond to N — S slices on the surface of widths of 0.16, 0.32 and 0.64 deg in longitude, respectively. The transmitter power Pz was taken to be 400 kW, operating at 8495 MHz, so A = 3.53 cm. The gains GT and G, were taken to be equal, and these values were deduced from data provided by Freiley (Ref. 3). JPL DEEP SPACE NETWORK PROGRESS REPORT 42-29

A nominal value of system efficiency of 0.40 was assumed from the data of Ref. 3. This value corresponds to a value 1 a lower than the mean transmit system efficiency at an elevation of 70 deg. The corresponding antenna gains are 71.1 dB. The 4 sets of values of (A/,T) were subdivided into sets of different values of D, where D varied between 0.56 AU (closest approach during the 1975 opposition) and 1.5 AU. These subsets were, in turn, subdivided even further to correspond to roughness C = 50, 150, 300, 1000, 2000 and 5000. A total of 78 distinct sets of data frames were then generated from Eq. (4). A value of pa = 0.08 was assumed for all evaluations of Eq. (4). This value is an average obtained from previous radar probes of Mars. Although p0 varies between 0.01 and 0.15, most regions have a reflectivity close to 0.08. In practice, data frames similar to those of Fig. 2(b) are measured at regular time intervals. To improve the signal-to-noise ratio, several sequential data frames are usually added together. The magnitude of each spectral component then represents an energy. That is, a signal of intensity P — P(f,r) watts is integrated for t, seconds to produce Ft, joules. Now, t, should be long enough to allow a particular region on the planet's surface to rotate from one discrete doppler frequency to the next. In this analysis, t, was chosen such that the planet rotated about 0.75 of that distance. For example, when A/ = 36.2 Hz (0.16 deg in longitude), t, was chosen to be 30 seconds, an interval in which the planet rotates 0.12 deg. The superimposing of a noisy signal of the proper magnitude was performed in the following manner. A series of random numbers with a variance of 1 .0 was generated. The scale of the variance was chosen by noting that the receiver noise power is fcT8Af watts for each spectral component, where k is Botzmann's constant and Ts is the system noise temperature. In time t, the mean energy obtained by integrating this component of the noise is kT,±ft, and the variance associated with the measurement of this component is (kT,)2£ft,. The measurement of the planetary component Pt, also is subject to random fluctuations. The total variance is calculated assuming that the wideband receiver component and the planetary component are each nearly Gaussian random processes. (They are in fact Rayleigh processes in which the mean is much larger than the root-mean-square fluctuation.) The total variance is then (kT,Ytft, + (Pt,)2/

In the generation of the series of random numbers it was assumed that Pt, < < kT&ft,, so that the planetary component of the variance could be ignored. The series 97

of random numbers, so scaled, and the mean value of the receiver noise were added to the function P(/,T) to obtain a simulated data frame. T, was taken to be 23 K. A data frame similar to Fig. 2(b) was generated from the noisefree frame of Fig. 2(a) in the above manner. The data in Fig. 2(b) correspond to D = 0.56 AU and C = 300. The constant wide-band component of the receiver noise has been subtracted. A total of 70 data frames containing independent additive noise, representing integrations over ti seconds, were generated to provide a good measure of the statistics of interest. IV. The Delay Measurements In practice, one cannot probe the planet's surface with a monostatic radar system (one antenna) on a continuous basis, since the transmitter must be turned off during reception. Hence, the simulated data frames were arranged in time to duplicate the case in which the radar signal is transmitted for a time interval equal to the round-trip time between Earth and Mars, and then received for one round-trip time. Reception immediately follows transmission for an equal time interval. Clearly, in one round-trip time one will usually collect several data frames, each representing an integration of t, seconds. Since the transmitter is not on continuously, only % of the available angles of incidence will be probed. A view window, of width equal to the amount of rotation accomplished in one round-trip time, slides over the surface allowing some angles of incidence and omitting others. The results of the delay measurements are presented in Tables 1-4. At first, the radar system parameters T and Af were chosen to be equal to those used in earlier work on Mars at 2388 MHz. The doppler shifts were scaled from 2388 to 8495 MHz such that A/ corresponded to a longitude interval AL of 0.16 deg. At each of the four values of D in Table 1, six values of roughness C were chosen to cover the range expected at 8495 MHz. A number NT (between 90 and 120) composite delay functions, each representing a different mixture of angles of incidence, were available for each combination of D and C. If the peak amplitude of a composite delay function was 2.5 to 3 times larger than the rms noise level, the planet was considered detected and the corresponding delay T was recorded. However, in ND detections, a certain number NF are false detections which usually occur in the weak signal case. Values of T which placed the planet more than T fis away from the known position of the 98

planet were considered false detections. The fraction Pj of successful detections and the fraction Pe of these detections that were false are listed in Table 1 and calculated from Np-N, NT

(5)

The values of ND, the mean TJO in the range estimates, and the associated rms fluctuation o-TO presented in Table 1 represent averages over all the available data. However, some of the composite delay functions contain contributions from angles of incidence primarily near 0 deg (the maximum is about 2 deg in this simulation). These delay functions were isolated and, finding Nc of them, the mean T&C of this set and the associated rms fluctuations 6 is evidence of the decreasing peak amplitude. By includinly only the values of r for which nd < 6 in the statistics, a true representation of the measurement accuracy is obtained. Including all available values of T produces a larger variance because of the systematic drift in T with window position. The mean n,c is a function of the roughness parameter C. In Fig. 4(a) the measurements of T are presented vs nd for C = 150 at a distance of 0.56 AU. The drift in r with nd is not as extreme as in Fig. 3(a) since the backscatter function varies more slowly with 6. Note however that TJ,C for nd < 6 is not identical to the similar value in Fig. 3(a). This bias is again caused by the retarded, flatter delay functions characteristic of low values of C or JPL DEEP SPACE NETWORK PROGRESS REPORT 42-29

larger values of 6. The data of Fig. 4(b), corresponding to D = 0.8 AU, show how small signal-to-noise ratios mask the effects discussed above. At opposition D = 0.56 AU. The results of Table 1 indicate that maximum ranging accuracies of 40 to 300 ns can be obtained. The systematic changes of T with nd and C are large compared to these hypothetical accuracies. It will then be desirable to apply corrections to the estimates of T to obtain the minimum possible rms fluctuations.

The data of Tables 3-4 were obtained in a search of the data-frame parameters which ensure detection of the planet Mars at the start of the 1975 series of measurements (during August, when Mars is at 1.2 AU). The parameters underlying Table 4 (T = 12 ps, AL = 0.64 deg) provide a reasonable probability of detection of rough as well as smooth surfaces at 1.2 AU. These are the parameters to be used at the start of the series of measurements. Tables 2 and 3 are useful as an aid in determining what T and AL should be as Mars progresses towards opposition.

References 1. Hagfors, T., "Backscattering from an Undulating Surface with Applications to Radar Returns from the Moon;" }GR, 69, pp. 3779-3784,1964. 2. Hagfors, T., Radar Astronomy, Evans, J. V., and Hagfors, T., eds., Chapter 4, pp. 187-218, McGraw-Hill, New York, 1968. 3. Freiley, A. J., "DSS-14 XKR Cone Performance," JPL Interoffice Memo No. 3331-75-001, Mar. 10,1975 (an internal document).

JPL DEEP SPACE NETWORK PROGRESS REPORT 42-29

99

Table 1. Detection probability and a- for T = 6 us, AL = 0.16 deg, p,( = 0.08

r* %

P* %

ND

"TV /JS

50 150 300 1000 2000 5000

98 100 100 100 100 100

1 0 0 0 0 0

118 120 120 120 120 120

0.44 0.26 0.31 0.31 0.38 0.45

50 150 300 1000 2000 5000

56 97 100 100 100 100

10 0 0 0 0 0

65 113 117 117 117 117

1.33 0.65 0.62 0.39 0.40 0.54

50 150 300 1000 2000 5000

3 62 83 95 95 92

57 1 1 0 0 0

4 76 102 117 117 113

1.80 1.18 0.72 0.62 0.55 0.57

50 150 300 1000 2000 5000

2 38 73 86 91 88

50 10 3 0 0 0

2 38 73 86 91 88

1.34 1.52 0.94 0.45 0.54 0.50

5, 0.56

0.80

1.00

1.14

100

6o> US

NO

"re, /tS

rte> /*s

2.6 2.4 2.3 2.0 1.7 1.4

64 64 64 64 56 56

0.30 0.12 0.08 0.09 0.04 0.04

2.4 2.25 2.1

40 61 61 61 55 55 _

1.38 0.42 0.15 0.11 0.04 0.04

42 54 58 55 52 _

0.98 0.57 0.33 0.32 0.22

T

29 39 50 52 49

_

— 1.44 0.80 0.38 0.45 0.35

1.75 1.4 1.1

_ _ — -

JPL DEEP SPACE NETWORK PROGRESS REPORT 42-29

Table 2. Detection probability and , = 0.08

D,

AU

C

1.00

50 150 300 1000 2000 5000

1.14

50 150 300 1000 2000 5000

1.50

50 150 300 1000 2000 5000

P.,

%

*,

"TO'

12 81 82 93 94 93

_ 3 3 0 0 0

13 91 83 94 95 94

1.09 0.81 0.61 0.49 0.74

4 60 82 93 94 93

_

6 3 0 0 0

4 61 83 94 95 94

1.15 1.50 0.81 0.61 0.49 0.74

_

_

_

_

30 76 83 84

10 0 0 0

26 67 73 74

1.37 0.53 0.63 0.45

r

bo>

Tic-

"e

/is

IIS

8 56 46 52 47 46

1.18 1.24 0.68 0.58 0.56 0.54

2.5 2.5 2.0 1.6 1.2

_

_

_

34 46 52 47 46

1.50 0.68 0.58 0.56 0.54

_

_

_

_

-

20 41 37 37

1.28 0.59 0.65 0.51

-

1.47

2.5 2.5 2.0 1.6 1.5

—

ORIGINAL PAGE is POOR QUALITY

JPL DEEP SPACE NETWORK PROGRESS REPORT 42-29

101

Table 3. Detection probability and OT for T = 6 /is, AL = 0.64 deg, />„ = 0.08

D, AU

C

/US

JUS

»,

"reps

Tbc>

%'

v.

CT

%'

3.3 2.7 2.7 2.2 1.7 1.4

31 65 70 70 53 53

1.72 0.98 0.65 0.51 0.29 0.20

3.1 2.9 2.6 2.0 1.5 1.1 _

_

6 48 57 62 49 50 _

2.0 1.55 0.84 0.53 0.56 0.82 _

_

7 27 44 37 37

1.40 1.20 0.65 0.46 0.25

-

6o»

1.00

50 150 300 1000 2000 5000

46 92 100 100 100 100

12 1 0 0 0 0

49 98 106 106 106 106

1.92 0.93 1.00 0.91 0.61 0.67

1.14

50 150 300 1000 2000 5000

11 78 95 100 100 98

31 6 0 0 0 1

10 74 90 95 94 93 _

1.60 1.50 1.00 0.75 0.64 0.71 _

8 44 69 71 75

1.5 1.62 0.72 0.47 0.64

_

1.50

102

T

TO»

50 150 300 1000 2000 5000

9 49 78

80 84

_ 5 0 0 0

MS

JPL DEEP SPACE NETWORK PROGRESS REPORT 42-29

Table 4. Detection probability and
AU

1.00

C 50 150 300 1000 2000 5000

1.14

50 150 300 1000 2000 5000

1.50

50 150 300 1000 2000 5000

ff

TO»

T

60»

%

%

N0

Its

its

*e

Its

82 100 100 100 100 100

4 0 0 0 0 0

91 111 111 111 111 111

2.62 1.48 1.10 0.78 1.12 1.48

5.4 5.0 4.4 3.4 2.8 7.0

86 103 103 103 53 53

2.66 1.50 0.74 0.70 0.32 0.36

44 91 98 100 98 95

10 2 1 0 0 0

49 101 109 111 109 106

3.40 2.00 1.75 1.28 1.44 0.93

30 63 70 71 55 51

3.40 2.20 1.96 0.92 0.77 1.14

_

_

_

_

30 68 76 80 80

10 0

1 0 0

JPL DEEP SPACE NETWORK PROGRESS REPORT 42-29

30 69 77 81 ' 80

3.10 1.84 1.08 1.08 1.04

_

_

_

19 42 44 38 37

3.60 1.92 1.10 1.38 1.30

T

%

5.4 5.0 4.4 3.2 2.4 1.6

_ _ -

103

3.5,1

POSITIVE DOPPLER SHIFT

EARTH Fig. 1. Partitioning of Mars by the radar system

104

JPL DEEP SPACE NETWORK PROGRESS REPORT 42-29

90

30

15

-1.12

1.16

-1.12

DOPPLEK SHIFT, kHz

Fig. 2. Received power vs doppler shift and delay for -if = 36.2 Hz, T = 6^8, p0 = 0.08, and C = 300: (a) noise-free case, (b) noisy case (see text for noise parameters)

JPL DEEP SPACE NETWORK PROGRESS REPORT 42-29

105

T

i

1

1

1

1 (b)

(a)

-

—

x

X

x

••

x

*********** S* w

1

1

1

1

I 10

1

1

X

1

^

XX

1

1

1

1

10

Fig. 3. Estimation of r MS the centroid n,, of the angle-of-incidence window for C = 5000: (a) 0 = 0.56 All, (b) D = 1.14 AU

(a)

(b)

x

*»:» »:»

-*

*, :«"**«««

„

x x

10

10

Fig. 4. Estimation of - vs the centroid n,, of the angle-of-incidence window for C = 150: (a) O = 0.56 AU, (b) D = 0.8 AU

106

JPL DEEP SPACE NETWORK PROGRESS REPORT 42-29

Geophysical Research Abstracts, Vol. 9, 01794, 2007 SRef-ID: 1607-7962/gra/EGU2007-A-01794 © European Geosciences Union 2007

The Red Soil on Mars as a proof for water and vegetation! R.Paepe GEOBOUND International, BV MUHS, The Hague, The Netherlands ([email protected] / Phone: +31-703-520510)

Red Soils on Earth are common features. Actually, what does the label “soil” stands for? It is used by so many people most of them with no training in soil science or in the related field of geology. And yet, everybody uses “Soil” as a simple connotation to indicate the surface, floor, territory, base/bottom, ground; or any kind of loose earth. And when it is red, it is called Red Soil. However, as a concept in soil science a Red Soil means something quite different: it then relates to a thorough soil/pedological weathering most often originating under tropical climatic conditions. The latter is characterised by specific sediment differentiation in the uppermost geological layers as to structure, texture and development of successive soil horizons. The latter biochemical process is a result of the clay/humic/Fe-sesquioxides vertical transport in the surface layers under the aegis of leaching respectively enrichment enhanced along the roots of any kind of vegetation cover. This process is called “pedogenesis” or soil development resulting in the development of a series of specific “soil” horizons in the strict pedological sense. Depending on the nature of the parent material (hard or loose) and of the prevailing climatic conditions, different soil types may be generated which are compiled in the international soil classification system. In reverse, from the soil type former conditions of climate and vegetation cover may eventually be disentangled. Despite the fact that pedology has the state of a well developed science in earth sciences the term “soil” as stated above has still different meanings and connotations depending on the professional field in which it is being considered and not at least on the skilfulness of the scientist involved. In fact numerous geo-scientists misuse the name too. And what about the scientists not acquainted with earth science at all? This is absolutely true in the field of astrobiology. What is then the meaning of the label “Red Soil” on Mars, Venus and other planets? In fact are they really “Soils” as defined

above or just simply red coloured (pediment) surfaces as the ones covering broad extensions in the tropical regions of Brazil and Congo? In fact, soil weathering should be clearly dissociated from all other types of rock alteration processes. Moreover soil composition, especially clay – phyllosilicates, display characteristic features enabling detection of real pedogenetic processes. Close observation of the impact traces at the Mars module site as well as the recent detection of phyllosilicates clays on Mars, may lead to firm indicators about pedogenesis processes on Mars. This opens new possibilities for the study of soil development similar to earthly soil processes on Mars and perhaps on other planets of the Solar system as well. Bacteria occur in great amounts in soils on Earth. Both aerobic and anaerobic bacteria occur so that a great variety of species is shown. Most unexpectedly there number is higher in desert environments rather than in moist places like the Amazone. Hence, soil cyanobacteria play an important role in the building of microbiotic crusts in extreme environments of drought and cold like Antarctica. Cyanobacteria also induce important biochemical cycles such as the nitrogen-fixation in soils. Geologically their origin may be far remote in time so that it may be assumed that they are time-resistant as well. Therefore soils of extreme desert conditions, cold and warm, on both Earth and Mars may contain great amounts of such resistant bacteria. Soils in the pedological sense if present on Mars and other Planets may then likely open new broad fields of investigation which research has hitherto been somewhat neglected. As a consequence, now that phylosilicates have been detected on Mars the role of water in the soil-weathering process of clays has undoubtedly been proved. This could furthermore imply that not only water and soil weathering / pedogenesis extended over the entire surface of Mars, but a vegetation cover as well. The far too general connotation of ‘soil’ should then be reconsidered as a true soil concept inferring both water and vegetation in its development. Hence, the relationship between soil development and vegetation/bacterial life on the surface of Mars opens up new broad possibilities for studies in astrobiology. Soils in Space and their related cyanobacterial content should become the genuine research for all evidences of real soil development outside planet Earth in our Solar System.

Chapter 6: Viking and the Resources of Mars Additional automated missions will most certainly occur, but the ultimate scientific study of Mars will be realized only with the coming of man—man who can conduct seismic and electromagnetic sounding surveys; who can launch balloons, drive rovers, establish geologic field relations, select rock samples and dissect them under the microscope; who can track clouds and witness other meteorological transients; who can drill for permafrost, examine core tubes, and insert heat-flow probes; and who, with his inimitable capacity for application of scientific insight and methodology, can pursue the quest for indigenous life forms and perhaps discover the fossilized remains of an earlier biosphere. (Benton Clark, 1978)1

The New Mars In the 1960s, most automated missions beyond lowEarth orbit—the Rangers, Surveyors, and Lunar Orbiters—supported the piloted Apollo program. In the 1970s, as NASA’s piloted program contracted to lowEarth orbit, its automated program expanded beyond the Moon. Sophisticated robots flew by Mercury, Jupiter, and Saturn, and orbited and landed on Venus and Mars. Though they were not tailored to serve as precursors to human expeditions in the manner of the Rangers, Surveyors, and Lunar Orbiters, the automated missions to Mars in the 1970s shaped the second period of piloted Mars mission planning, which began in about 1981. The first of these missions, Mariner 9, took advantage of the favorable Earth-Mars transfer opportunity associated with the August 1971 opposition to carry enough propellant to enter Mars orbit. It was launched from Cape Kennedy on 30 May 1971. In September, as Mariner 9 made its way toward Mars, Earth-based astronomers observing the planet through telescopes saw a bright cloud denoting the onset of a dust storm. By mid-October it had become the largest on record. Wind-blown dust obscured the entire surface, raising fears that Mariner 9 might not be able to map the planet from orbit as planned.2 On 14 November 1971, after a 167-day Earth-Mars transfer, Mariner 9 fired its engine for just over 15 min-

utes to slow down and become Mars’ first artificial satellite. Dust still veiled the planet, so mission controllers pointed the spacecraft’s cameras at the small Martian moons Phobos and Deimos. In Earth-based telescopes they were mere dots nearly lost in Mars’ red glare. In Mariner 9 images, Phobos was marked by parallel cracks extending from a large crater. Apparently the impact that gouged the crater had nearly smashed the little moon. Deimos, Mars’ more distant satellite, had a less dramatic, dustier landscape. The giant dust storm subsided during December, theatrically unveiling a surprising world. Mars was neither the dying red Earth espoused by Percival Lowell nor the dead red moon glimpsed by the flyby Mariners.3 From its long-term orbital vantage point, Mariner 9 found Mars to be two-faced, with smooth northern lowlands and cratered southern highlands. The missions to the Moon confirmed that a relationship exists between crater density and age—the more densely cratered a region, the older it is. Hence, Mars has an ancient hemisphere and a relatively young hemisphere. Mars is a small world—half Earth’s diameter—with large features. The Valles Marineris canyons, for example, span more than 4,000 kilometers along Mars’ equator. Nix Olympica, imaged by Mariner 6 and Mariner 7 from afar and widely interpreted as a bright crater, turned out to be a shield volcano 25 kilometers tall and 600 kilometers wide at its base. Renamed Olympus Mons (“Mount Olympus”), it stands at one edge of the Tharsis Plateau, a continentsized tectonic bulge dominating half the planet. Three other shield volcanoes on the scale of Olympus Mons form a line across Tharsis’ center. Most exciting for those interested in Martian life were signs of water. Mariner 9 charted channels tens of kilometers wide. Some contain streamlined “islands” apparently carved by enormous rushing floods. Many of the giant channels originate in the southern highlands and open out onto the smooth northern plains. The northern plains preserve rampart craters—also called “splosh” craters—which scientists believe were formed by asteroid impacts in permafrost. The heat of impact apparently melted subsurface ice, which flowed outward from the impact as a slurry of red mud, then refroze.4

Humans to Mars: Fifty Years of Mission Planning, 1950–2000

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Chapter 6: Viking and the Resources of Mars

Mariner 9 depleted its nitrogen attitude-control propellant on 27 October 1972, after returning more than 7,200 images to Earth. Controllers quickly lost radio contact as it tumbled out of control. A week later, on 6 November 1972, mission planners using Mariner 9 images announced five candidate Viking landing sites.5

repeated the tests several times with similar equivocal results. Most scientists interpreted the Viking results as indicative of reactive soil chemistry produced by ultraviolet radiation interactions with Martian dirt, not of life. The reactive chemistry probably destroys any organic molecules.7

Viking 1 left Earth on 20 August 1975 and arrived in Mars orbit on 19 June 1976. Its twin, Viking 2, left Earth on 9 September 1975 and arrived at Mars on 7 August 1976. The spacecraft consisted of a nuclearpowered lander and a solar-powered orbiter. The Viking 1 lander separated from its orbiter and touched down successfully in eastern Chryse Planitia on 20 July 1976. Viking 2 alighted near the crater Mie in Utopia Planitia on 3 September 1976.

Improved cameras on the Viking orbiters, meanwhile, added detail to Mariner 9’s Mars map. They imaged polygonal patterns on the smooth northern plains resembling those formed by permafrost in Earth’s Arctic regions. Some craters—Gusev, for example— looked to be filled in by sediments and had walls breached by sinuous channels. Perhaps they once held ice-clad lakes.

The first color images from the Viking 1 lander showed cinnamon-red dirt, gray rocks, and a blue sky. The sky color turned out to be a processing error based on preconceived notions of what a sky should look like. When the images were corrected, Mars’ sky turned dusky pink with wind-borne dust.6 The Vikings confirmed the old notion that Mars is the solar system planet most like Earth, but only because the other planets are even more alien and hostile. A human dropped unprotected on Mars’ red sands would gasp painfully in the thin carbon dioxide atmosphere, lose consciousness in seconds, and perish within two minutes. Unattenuated solar ultraviolet radiation would blacken the corpse, for Mars has no ozone layer. The body would freeze rapidly, then mummify as the thin, parched atmosphere leeched away its moisture. By the time the Vikings landed, almost no one believed any longer that multicellular living things could exist on Mars. They held out hope, however, for hardy singlecelled bacteria. On 28 July 1976, the Viking 1 lander scooped dirt from the top few centimeters of Mars’ surface and distributed it among three exobiology detectors and two spectrometers. The instruments returned identical equivocal readings—strong positive responses that tailed off, weak positive responses that could not be duplicated in the same sample, and, most puzzling, an absence of any organic compounds the instruments were designed to detect. Viking 1 and Viking 2 each scooped additional samples— even pushing aside a rock to sample underneath—and

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The Viking images also revealed hundreds of river-size branching channels—called “valley networks”—in addition to the large outflow channels seen in Mariner 9 images. Though some were probably shaped by slowly melting subsurface ice, others appeared too finely branched to be the result of anything other than surface runoff from rain or melting snow. Ironically, most of the finely branched channels occurred in the southern hemisphere, the area that reminded people in the 1960s of Earth’s dead Moon. The flyby Mariners might have glimpsed channels among the Moonlike craters had their cameras had better resolution. Low pressure and temperature make free-standing water impossible on Mars today. The channels in the oldest part of Mars, the cratered southern highlands, seem to point to a time long ago when Mars had a dense, warm atmosphere. Perhaps Mars was clement enough for a sufficiently long period of time for life to form and leave fossils.8 The Viking landers and orbiters were gratifyingly longlived. The Viking 1 orbiter functioned until 7 August 1980. Together with the Viking 2 orbiter, it returned more than 51,500 images, mapping 97 percent of the surface at 300-meter resolution. Though required to operate for only 90 days, the Viking 1 lander, the last survivor of the four vehicles, returned data for more than six years. The durable robot explorer finally broke contact with Earth on 13 November 1982.9 Viking was a tremendous success, but it had been widely billed as a mission to seek Martian life. The inconclusive Viking exobiology results and negative inter-

Chapter 6: Viking and the Resources of Mars

pretation placed on them helped dampen public enthusiasm for Mars exploration for a decade. Yet Viking showed Mars to be eminently worth exploring. Moreover, Viking revealed abundant resources that might be used to explore it.

Living off the Land During the period that Mariner 9 and the Vikings revealed Mars to be a rich destination for explorers, almost no Mars expedition planning occurred inside or outside NASA. The Agency was preoccupied with developing the Space Shuttle, and Mars planners independent of NASA—who would make many contributions during the 1980s—were not yet active in significant numbers. Papers on In-Situ Resource Utilization (ISRU) were among the first signs of re-awakening interest in piloted Mars mission planning. ISRU is an old concept, dating on Earth to prehistory. ISRU can be defined as using the resources of a place to assist in its exploration—the phrase “living off the land” is essentially synonymous. In the context of space exploration, ISRU enables spacecraft weight minimization. If a spacecraft can, for example, collect propellants at its destination, those propellants need not be transported at great expense from Earth’s surface. In the 1960s, ISRU was studied largely in hopes of providing life-support consumables. By the 1980s, the propellant production potential of ISRU predominated. NASA first formally considered ISRU in 1962, when it set up the Working Group on Extraterrestrial Resources (WGER). The WGER, which met throughout the 1960s, focused on lunar resources, not Martian. This was because more data were available on lunar resource potential, and because lunar resource use was, in the Apollo era, potentially more relevant to NASA’s activities.10 The UMPIRE study (1963-1964) recommended applying ISRU to establish and maintain a Mars base during long conjunction-class surface stays. Doing this would, of course, demand more data on what resources were available on Mars. NASA Marshall’s UMPIRE summary report stated that “[t]his information, whether it is obtained by unmanned probes or by manned [flyby or orbiter] reconnaissance missions, would

make such a base possible,” making the “ ‘cost effectiveness’ of Mars exploration . . . much more reasonable than [for] the short excursions.”11 Fifteen years after UMPIRE, the Vikings at last produced the in-situ data set required for serious consideration of Mars ISRU. The first effort to assess the potential of Martian propellant production based on Viking data spun off a 1977-78 NASA JPL study of an automated Mars sample-return mission proposed as a follow-on to the Viking program. Louis Friedman headed the study, which was initially inspired by President Gerald Ford’s apparently casual mention of a possible “Viking 3” mission soon after the successful Viking 1 landing.12 Robert Ash, an Old Dominion University professor working at JPL, and JPL staffers William Dowler and Giulio Varsi published their results in the July-August 1978 issue of the refereed journal Acta Astronautica.13 They examined three propellant combinations. Liquid carbon monoxide and liquid oxygen, they found, were easy to produce from Martian atmospheric carbon dioxide, but they rejected this combination because it produced only 30 percent as much thrust as liquid hydrogen/liquid oxygen. Electrolysis (splitting) of Martian water could produce hydrogen/oxygen, but they rejected this combination because heavy, energyhungry cooling systems were necessary to keep the hydrogen liquid, thus negating the weight-reduction advantage of in-situ propellant manufacture. Liquid methane/liquid oxygen constituted a good compromise, they found, because it yields 80 percent of hydrogen/oxygen’s thrust, yet methane remains liquid at higher temperatures, and thus is easier to store. The Martian propellant factory would manufacture methane using a chemical reaction discovered in 1897 by French chemist Paul Sabatier. In the Sabatier reaction, carbon dioxide is combined with hydrogen in the presence of a nickel or ruthenium catalyst to produce water and methane. The manufacture of methane and oxygen on Mars would begin with electrolysis of Martian water. The resultant oxygen would be stored and the hydrogen reacted with carbon dioxide from Mars’ atmosphere using the Sabatier process. The methane would be stored and the water electrolyzed to continue the propellant production process.

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Chapter 6: Viking and the Resources of Mars

Ash, Dowler, and Varsi estimated that launching a onekilogram sample of Martian soil direct to Earth would need 3.8 metric tons of methane/oxygen, while launching a piloted ascent vehicle into Mars orbit would need 13.9 metric tons. These are large quantities of propellant, so conjunction-class trajectories with Mars surface stay-times of at least 400 days would be necessary to provide enough time for propellant manufacture. Benton Clark, with Martin Marietta (Viking’s prime contractor) in Denver, published the first papers exploring the life-support implications of the Viking results. His 1978 paper entitled “The Viking Results— The Case for Man on Mars” pointed out that every kilogram of food, water, or oxygen that had to be shipped from Earth meant that a kilogram of science equipment, shelter structure, or ascent rocket propellant could not be sent.14 Clark estimated that supplies for a 10-person, 1,000-day conjunction-class Mars expedition would weigh 58 metric tons, or about “one hundred times the mass of the crew-members themselves.” The expedition could, however, reduce supply weight, thereby either reducing spacecraft weight or increasing weight available for other items, by extracting water from Martian dirt and splitting oxygen from Martian atmospheric carbon dioxide during its 400-day Mars surface stay. Clark wrote that Mars offered many other ISRU possibilities, but that they probably could not be exploited until a long-term Mars base was established. This was because they required structures, processing equipment, or quantities of power unlikely to be available to early expeditions. Crop growth using the “extremely

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salty” Martian soil, for example, would probably have to await availability of equipment for “pre-processing . . . to eliminate toxic components.”15 The Vikings’ robotic scoops barely scratched the Martian surface, yet they found useful materials such as silicon, calcium, chlorine, iron, and titanium. Clark pointed out that these could supply a Mars base with cement, glass, metals, halides, and sulfuric acid. Carbon from atmospheric carbon dioxide could serve clever Martians as a foundation for building organic compounds, the basis of plastics, paper, and elastomers. Hydrogen peroxide made from water could serve as powerful fuel for rockets, rovers, and powered equipment such as drills. During the 1980s, the Mars ISRU concept generated papers by many authors, as well as initial experimentation.16 Robert Ash, for example, developed experimental Mars ISRU hardware at Old Dominion University with modest funding support from NASA Langley17 and from a non-government space advocacy group, The Planetary Society.18 That a private organization would fund such work was significant. Before ISRU could make a major impact, piloted Mars mission planning had to awaken more fully from its decade-long post-Apollo slumber. Post-Apollo Mars planning occurred initially outside official NASA auspices. This constituted a sea-change in Mars planning—up to the 1970s, virtually all Mars planning was government-originated. In the 1980s, as will be seen in the coming chapters, individuals and organizations outside the government took on a central, shaping role.