Friday, October 1, 2004
Dept of Geological Sciences, SDSU,
"Atmospheres and Oceans of the Terrestrial Planets"
2:00 pm in room P-148
Abstract: The atmospheres (including water) of the terrestrial planets have two sources: outgassing from the interior and impacting of comets. The bulk of the atmospheres and oceans collected early in solar system history. What happened to the original constituents is a function of planetary mass and distance from the Sun. Small planets such as Mercury and the Moon lost all original gases whereas Venus and the Earth lost only hydrogen and helium. Mars, intermediate in size and farther from the Sun, had an ocean and much denser atmosphere early in solar system history but gradually lost gases and is now cold, barren and with a sparse residual atmosphere. The water of Venus underwent photochemical dissociation and resulted in a dense carbon dioxide atmosphere whereas the Earth stored significant gaseous compounds and liquid water. Dissociation of water on the Earth is going on at a much slower rate, but will ultimately transform the planet into a milder version of Venus.