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Project Progress

Coevolution of Earth and Mars (dm)

Previously suggested gases for terraforming Mars include the CFC’s and SF6. Recent, detailed calculations for C2F6 and the CFC’s have led to optimism about terraforming. Some means other than greenhouse gases must be used for the initial warming, as no known gas mixture in a small total column amount will absorb strongly at current martian pressure (600 Pa). We introduced some new candidate gases, and we framed our inquiry by asking what mixture of trace gases could sustain an earthlike temperature if Mars were somehow endowed with an earthlike atmospheric composition and earthlike surface pressure. We suggested that a 70K greenhouse effect might be maintainable with as little as 5×10^22 m-2 column amount of a mixture of “designer” greenhouse molecules. This molecular column corresponds to about 240 ppbv in Earth’s atmosphere.