The Ozone Layer

The ozone layer

Early Earth  Early earth didn’t have any oxygen

Early Earth  3.5 billion years ago, single-celled, blue-green cyanobacteria  They captured the energy of the sun to make food, releasing oxygen as a waste product.  Little by little they turned the atmosphere into breathable air, opening the way to the diversity of life that followed.

http://user.uni-frankfurt.de/~schauder/cyanos/image9.jpg

http://www.mfe.govt.nz/publications/ser/snapshot-lake-water-qualitynov06/html/images/cyanobacteria.jpg

Early Earth  Later on, larger plants developed and increased the amount of oxygen in the air

The atmosphere  Layer of gases that surround the earth  The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through the greenhouse effect, and reducing temperature extremes between day and night.

http://upload.wikimedia.org/wikipedia/commons/b/be/Top_of_Atmosphere.jpg

The atmosphere  The atmosphere is divided into layers  The ozone layer is in the stratosphere  The ozone layer is where large amounts of the ozone molecule are present

What is ozone?  Ozone is a molecule that has 3 oxygen atoms

 Oxygen is a molecule that has 2 oxygen atoms (this is what we breathe)

What does the ozone do for us?  Like a good pair of sunglasses, the ozone layer acts like a natural filter, blocking out most of the sun's harmful UV (ultraviolet) rays. Without the ozone layer, more people would get sunburns, skin cancer and cataracts. Plants and animals would also be affected. So we can think of the ozone layer as our planet's own protective sunscreen.

Ozone damage  http:// www.youtube.com/watch?v =qUfVMogIdr8

http://images.google.com/imgres?imgurl=http://www.nasa.gov/images/content/60938main_ozone_hole.jpg&imgrefurl=http://www.nasa.gov/audience/foreducators/k4/features/F_Ozone_Friend_or_Foe_prt.htm&usg=__xkw5D7VL_dyfdfQJtYEzYZQ8Efw=&h=317&w=330&sz=50&hl=en&start=16&sig2=e9F0GO7vjg2mMxtZyqM7tA&um=1&tbnid=PfOs77CRXvF -fM:&tbnh=114&tbnw=119&ei=8RtFSYHNEYyGsAORmbiZBA&prev=/images%3Fq%3Dozone%2Bhole%26um%3D1%26hl%3Den%26rls%3Dcom.microsoft:*%26sa%3DN

Ozone damage  CFCs (chloroflorocarbons) and other ozone-depleting chemicals were first mass-produced in the 1950s for use as refrigerants, industrial solvents, cleaning fluids and agents in making foam products. In the late 1960s, they were widely used in spray cans. In 1980, Canada and other countries banned CFC use in aerosol sprays.

Ozone damage  Although CFCs do not harm the environment near the ground, they slowly travel upwards to the ozone layer where they are broken down by UV light into chlorine atoms. Here, the chlorine atoms eat away at the ozone like pac-men.

Question  The planet Mars has little atmosphere. At any given location, temperatures change daily from far below zero to above 100 degrees C. What is Mars lacking that would explain these extremes?

Mars lacks an ozone layer in the upper atmosphere