SimEarth: Terraforming Mars by the Numbers

An anonymous reader writes "Today NASA has an online terraforming simulation based on the McKay/Zubrin/Fogg model of Mars' weather modification. The simulation shows that the greening of Mars can be done in at least three ways: 1) mirrors melting stored carbon dioxide in tropical soil and polar dry ice; 2) a fluorocarbon (CFC) factory; 3) blowing a vent thruster in the side of a methane-rich asteroid and engineering a collision (perhaps many impacts, but a mere 0.3 km/s impulse drive if using an outer solar system asteroid, such as Chiron, beyond Saturn). Irrespective of the merits or wisdom of these huge engineering projects, their simulation allows moving back the clock to a previous time when Mars was blanketed by greenhouse gases, and thus much warmer."

Comments

Re:Magnetic field.

[Bob Kopp]

It's not clear whether Mars had a thick atmosphere to lose. If it did, though, there's only two things that could have happened to the heavy molecules (e.g. CO2) that it contained: they could have been sequestered in reservoirs such as carbonates (not much of which have been yet found), or they could have been lost to space through non-thermal processes. In the last 3.5 billion years on so, the major non-thermal loss process is sputtering by the solar wind, as you say.

Whether a terraformed planet is usably terraformed is a matter of time scales. Models suggests that between 0.1 and 3 bar CO2 could have been lost through sputtering over a period of about 3.5 billion years. Taking the maximum rate, this is an annual loss of less than 1 part per billion per year, or 0.1 bar in 100 million years. Thus no significant loss due to sputtering would occur on the time scale of human civilization.

I vaguely recall seeing calculations for the duration of an atmosphere on a terraformed Moon. IIRC, even such an atmosphere might last for useful time scales; a 1 bar Earth-like atmosphere might last for several thousand years before being lost due to thermal escape and sputtering.