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There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
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Famed late NASA astronomer Carl Sagan first hypothesized that the reason early Earth stayed warm although the sun shone dimly had to do with a greenhouse effect involving a gas mixture different from that in Earth's atmosphere today. He suspected high ammonia levels, which proved chemically less feasible. Today, many scientists suspect the warming gas was methane. Credit: NASA-JPL
