ASTR 101 Chapter Notes - Chapter 2: Plate Tectonics, Extinction Event, Runaway Greenhouse Effect
5 Sep 2016
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Search for extrasolar planets is finding one that resembles our home planet. Planet has changed a lot over 4. 56 billion years. Alien astronomers would have seen our planet at different phases in its evolving history. Lots of rocks hitting it to keep it as water. Sun 75% to 85% as luminous as today. Atmosphere consisted of nitrogen, carbon dioxide, methane, water vapour. Primitive photosynthetic life appeared at 3. 4 billion years ago. Sun was at 85% to 95% as luminous as today. Oxygen builds up rapidly 2. 45 billion years ago. Origin of multicellular life 1. 2 billion years ago. Ice covers the surface all the way to the equator. Volcanic co2 emissions eventually melt most of the ice. Sun 90% to 95% as luminous as today. Atmosphere consisted of nitrogen, oxygen, water vapor and methane. Rapid diversification of animal life begins 543 million years ago. Atmosphere consists of nitrogen, oxygen, and argon: oxygen levels vary.
