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Unformatted text preview: 1 Extraterrestrial Life: Spring 2008 Extraterrestrial Life: Lecture #8 New homework: due next Thursday can post queries of general interest at www.et-life.blogspot.com Last time: long term climate regulation Today: dating of rocks and surfaces when was the Frst life on Earth? how has the atmosphere evolved over billions of years? which planets have been volcanically active, and when did that activity cease? Extraterrestrial Life: Spring 2008 Relative ages of terrain on Moon, Mars, Mercury etc can often be determined visually by looking at the cratering on the surface Young terrain: few impact craters are visible Newer impact craters overlap older ones, or cut across other features (e.g. channels) Saturation - so many craters that each new one destroys older ones Extraterrestrial Life: Spring 2008 Heavily cratered terrain: ~4.6 billion years old Younger terrain: ~3 billion years old Extraterrestrial Life: Spring 2008 Overall, the rate of cratering has declined since the early history of the Solar System time impact rate on the Moon Late heavy bombardment of the Moon ~1 billion years after Solar System formation? Extraterrestrial Life: Spring 2008 Venus has relatively few impact craters: small bodies will not penetrate the atmosphere lack of large craters suggests that the surface...
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This note was uploaded on 08/31/2009 for the course GEOL 3300 taught by Professor Staff during the Spring '08 term at Colorado.
- Spring '08