The Interpretation Of Space Data

THE INTERPRETATION OF SPACE DATA Roberto Bartali Introduction Most Solar System object, planets, satellites, comets and asteroid physical data, composition and surface characteristic was not well known until space age era. Artificial satellites changes dramatically our perception and knowledge of the Solar System giving many times a lot of surprises. In this essay I will try to explain and discuss the difference from what we know before and after the space exploration of the giant planet Jupiter and its satellite system. This work is splitted in two sections: before 1957 and after 1957, year that represent the beginning of scientific space exploration with the launch of the first satellite Sputnik. In the second half I discuss the new features and knowledge acquired thanks to the astronomical space explorations. The before 1957 era When Galileo point his telescope to Jupiter for the first time in 1610, astronomy and in particular Planetary Astronomy, change forever. The discover of the 4 biggest satellites (Figure 1) proved that Earth was not as special and unique as people thought, but just another peace of the Universal puzzle. Due to the limitations of the instrument used, not so much was added to Jovian System for 3 centuries; from Figure 1 Galileo manuscript of 1892 and 1957, many satellites satellite observation and atmospheric characteristics was discovered and studied, but earth atmosphere not aid to much to astronomy, but the biggest (5 meters) Mt. Palomar telescope shows that Jupiter is much more interesting than we suspect (Figure 2). The dense atmospheric clouds of hydrogen and methane occult the surface of the planet. Many belts, specially in the equatorial region was observed, but no much of their physical and chemical property was known. Spots and belts are always changing. The great Red Spot, the most spectacular feature, was discovered in 1664. Regarding to the Galilean Figure 2 Mt. Palomar picture of satellites (Io, Europa, Ganymede Jupiter and Callisto) very few things was known, because the apparent size as seen through a telescope is about 1 arc second. Best pictures only show a few dark areas, and most of their orbital data was approximate. Many perturbations of satellite movements was known but the reason for that remains unclear until some years ago. From observation data, astronomers described Io and Europa as rocky like the Moon; and Ganymede and Callisto made of ice and carbon dioxide. No rings was known and no suspect of an atmosphere. Due to the difficult to

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observe satellite and, in general planets, astronomers leave aside for many years this field, so a few scientist spent his time for that. The after 1957 era In the years around World War 2 first, and then during the Cold War, every field of technology, evolved very quickly, so in a few years we get supercomputers capable of trillions operation per second, spacecraft landing on Moon and planets, satellites leaving Solar System, man on the moon, enormous adaptive telescopes and interferometers, arrays of radiotelescopes, extremely sensitive imagine equipment, software algorithms making miracles with information, and many more Figure 3 marvels. Putting most of these Pioneer 10 technologies together on a satellite, we get spacecrafts like Pioneer (Figure 3), Voyager (Figure 4), Galileo (Figure 5), and The Hubble Space Telescope, HST (Figure 6) These scientific Satellites was specifically made for studiing Jupiter. Coincidently Galileo (the man) and Galileo (the spacecraft) made the most important discoveries of Jupiter system. Pioneer and Voyager discovered many features of the planet atmosphere (Figure 7), magnetic field and a system of 3 rings Figure 4 (Figure 9) around Jupiter, but Galileo and Voyager 1 its more sensitive instruments took the best images (Figure 8) and give us precise information about the planet and major satellites. When USA and URSS begins the space era, astronomers interested in planetology suddenly grows. Comparing Table 2 data its clear the advantage to send spacecraft to observe directly on the target. From almost nothing known Figure 5 Galileo about Galilean satellites, we get a landscape very interesting. Some features like magnetic fields, atmosphere, water ice are commonly for Galilean Satellites, these are the most unexpected surprises that spacecraft give to us.

Figure 6 Hubble Space Telescope

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Figure 7 Jupiter Great red Spot (Voyager picture)

Figure 8 Jupiter Great Red Spot (Galileo picture)

Figure 9 Júpiter rings (Galileo picture)

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Io Io is the nearest to Jupiter, is the second volcanic active body of the Solar System (Figure 10, 11), and the most one. Its surface is very young because eruptions change the landscape frequently, the enormous gravitational power of Jupiter kick off a ton of Io matter per second and continuously tidal forces change its shape. Volcanic activity erase any meteoric impact, the surface is almost plane but some mountain Figure 10 chain reach 9,000 meters Volcanic eruption on Io above the surface. Sulfurs and other chemical components of the lava offer a colored surface burst like geysers send to space through Jupiter sodium sulfurs at very high speed and they are trapped by its magnetic field. The core of Io is made of iron or iron sulfurs and this, together to moving masses and ionized jets, are possibly, a reason for the little magnetic field generated by the satellite. Io has also a thin sulfuric atmosphere and an ionosphere.

Figure 11 Io volcanos

Europa This is the most enigmatic satellite because of its many contrasting features. A little volcanism is suspected but not all scientist are in accord for this. The surface is mostly conformed by rocks and iced rocks. There are a few mountains and very few impact craters, some formations resembles craters but they are covered by ice. Europa surface are completely fractured (Figure 12) due to strong tidal forces from other satellites and Jupiter. This is because under the iced surface there are an ocean of liquid water and perhaps, due to mass Figure 12 Europa iced fractured surface movement and also a little of volcanism, there are warmer zones that may host some kind of life. The continuous movement of the inner liquid mass break and move apart giant parts of the iced surface like earth artic icebergs. As other Galilean satellites, Europa has a thin atmosphere of oxygen, above of 4

that there is a ionosphere. Some zones of the satellite instead of iced water has sulfuric ice, this is a counterpart to the possibility of find life, but on earth there are life near submarine volcanic gas plumes. The interest on this satellite is very high, so there are a mission planned for studying Europa and Ganymedes: Europa Express. Thank to the iced surface this satellite has the greater albedo. Ganymede This is the biggest of the 4 Galilean satellites and also the biggest satellite of the Solar System. It has a solid rocky core made of silicates. The surface is probably a thick crust of water ice. The core of Ganymede is made of silicates and is about the 50% of the mass. The surface is very fractured Figure 13) like Europa, but it is almost rocky made of silicates. There are many impact Figure 13 craters. Ganymede fractured surface

Callisto

Figure 14 Cratered surface of Callisto)

Callisto is the outermost Galilean satellite and with the lesser albedo. Its orbit is beyond the radiation belt of Jupiter. Under the crust there is an ocean of salt water. When a meteorite impact the surface, from the broken crust came out water and freezing, make a system of bright rays. Callisto surface is very old, it seems that nothing happened on it from billions years ago, there are many impact craters (Figure 14), there is no evidence of volcanism capable to refurbish the surface. is the most cratered body of the Solar System. It has a thin oxygen and carbon dioxide atmosphere. The surface are made by rocky silicates covered by ice, there are not high mountains. Callisto is the less denser satellite.

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TABLE 1 Jupiter missions NAME YEAR

Pioneer 10 Pioneer 11 Voyager 1 Voyager 2 Ulysses Galileo and its orbiter

1972 1973 1977 1977

HST

1990

1989

OBJECTIVES

Magnetic field, trapped charged particles, solar wind interactions Cloud tops, magnetic field Chemical composition of atmosphere, magnetosphere, satellites Chemical composition of atmosphere, magnetosphere, satellites Studying Jupiter when reach it, charged particles, solar wind Magnetosphere, satellites, comet crashing, atmospheric structures, chemical composition, thermal energy, energetic particles, electromagnetic waves. The probe enter the atmosphere and go down about 150 to 200 km. Photographic survey from outer earth atmosphere

Conclusion Technology and space probe give us a different and more realistic view of the Universe and even when there are many questions already on the air, we learn the way to get the right answer: Space Astronomy, because the only way to understand the Cosmos is using the best technology into space. References (1) (2) (3) (4) (5) (6) (7)

Andrenelli P., L´ASTRONOMO DILETTANTE, Sansoni, ed. 1968 Schroeder W., ASTRONOMIA PRATICA, Longanesi, ed.1967 Muller P., DIZIONARIO DI ASTRONOMIA, SEI, ed 1972 Brown, P.L., STAR AND PLANET SPOTTING, Blandford press, ed. 1974 Lowell B., CONOCIMIENTO ACTUAL DEL UNIVERSO, NCL, ed 1975 Morrison D., Samz J., VOYAGE TO JUPITER, NASA SP-439, ed. 1980 Beatty K., Petersen C., Chaikin A., THE NEW SOLAR SYSTEM, Cambridge Univ. Press, ed. 1999 (8) Freedman R., Kaufmann W.III, UNIVERSE, Freeman, ed.2002 (9) Cecchini G., IL CIELO, vol.1, UTET, ed.1969 (10) Fracastoro M., LA TERRA, IL SOLE E IL SISTEMA PLANETARIO, Osservatorio Pino Torinese, ed. 1968 (11) www.jpl.nasa.gov/galileo/ (12) www.ifa.hawaii.edu/sheppard/satellites/jup2003.html (13) www.solarview.com/eng/jupiter.htm (14) www.photojournal.jpl.nasa.gov/catalog (15) www.hubblesite.gov (16) www.seds.org/nineplanets/nineplanets/jupiter.html (17) http://seds.lpl.arizona.edu/billa/tnp/io.html (18) www.news.cornell.edu/releases/sept98/jupiter_rings.html (19) www.jpl.nasa.gov/galileo/io/fact.html (20) www.jpl.nasa.gov/galileo/europa/fact.html (21) www.jpl.nasa.gov/galileo/ganymede/fact.html (22) www.jpl.nasa.gov/galileo/callisto/fact.html 6

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