Free Astronomy Magazine September-October 2018

41 PLANETOLOGY T his animation transitions from an early, wet Mars to present-day dry Mars. [Created for the MAVEN mission by the Lunar and Plane- tary Institute] A rtist’s im- pression of the terraforming of Mars, from its current state to a livable world. [William Black] SEPTEMBER-OCTOBER 2018 atmospheric pres- sure and, therefore, the surface temper- ature. As a conse- quence, the atmo- spheric water vapor content would also increase, giving the greenhouse effect a further boost. The surface gravity of Mars is equal to 38% that of Earth’s. To achieve an at- mospheric pressure similar to that on Earth’s surface (1013.25 millibars at sea level), the vertical air mass must be sig- nificantly greater per unit area to compen- sate for the lower Martian gravity. That said, to live on the red planet, we might be con- tent with a lower pressure than what we are used to on Earth. Scientists estimate that, at only 190 millibars, a pressurized suit would no longer be necessary and a pure oxygen mask with positive pressure would be sufficient. At 240 millibars (almost ¼ of the average pressure at sea level), a stan- dard high-altitude respirator would suffice. It would obviously be necessary to wear pro- tective clothing against the most energetic photons and the most harmful charged par- ticles, which do not stop being a threat by merely increasing the amount of CO 2 in the more evident in the minds of scientists and futurists. As already mentioned, the primary objective is the thickening of the Martian atmos- phere. It’s like moving the clock back over three billion years to when some form of life on that planet was sustainable. The current Martian atmosphere produces a surface pressure of just 6 millibars (0.6% of the Earth’s). It is composed of 96% car- bon dioxide (CO 2 ), while the remaining 4% includes argon, nitrogen, oxygen and car- bon monoxide. CO 2 is a greenhouse gas - if it were possible to sublimate the CO 2 con- tained in the form of ice in the polar ice caps, in the ground and in the subsoil, it would be possible to significantly raise the