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Unformatted text preview: came cool enough to allow liquid water to rest on the surface. Life probably arose on Earth shortly after its formation, about 4 billion years ago. Life may have arisen in the deep ocean. Earths atmosphere has changed substantially through time. The most dramatic change began about 2 billion years ago when photosynthetic or-ganisms began producing large quantities of oxygen. Other planets and moons may haveor may have hadoceans....
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This note was uploaded on 10/07/2011 for the course OCS 1005 taught by Professor Condrey during the Spring '08 term at LSU.
- Spring '08