the rate is escapes into space isnt all that great. once you got an earth like atmosphere on mars you wouldnt need to worry about replenishing it for thousands of years. not to mention that the martian atmosphere, while only 1% as dense as earths, is almost entirely carbon dioxide meaning the martian atmosphere actually has far more co2 than ours in an absolute sense. plants in greenhouses would grow at an incredible rate if you simply warmed up and then pumped in straight martian atmosphere
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