Free Astronomy Magazine September-October 2018

44 SEPTEMBER-OCTOBER 2018 PLANETOLOGY T his infographic highlights the main sources that may contribute to the budget of martian CO2. Unfortunately, the mass of gas that can be released with the current technology is con- siderably lower than that needed to start the ter- raforming of Mars. [NASA] chain effects resulting from this would pro- mote the accumulation of liquid water on the surface in an amount estimated at 1/7 th of the flow of primordial oceans. If the shield proposed by Green does not prove to be as efficient as expected, some already known strategies could be imple- mented at the same time, designed to in- crease the temperature and accelerate the greenhouse effect. One of these strategies is to reduce the albedo of the regions in which the ice reserves of CO 2 and H 2 O are most concentrated, so that a higher absorp- tion of the heat coming from the Sun may favor its sublimation. The albedo reduction could be achieved by depositing dark pow- ders taken from the surfaces of Phobos and Deimos, or fostering the localized prolifer- ation of extremophile forms of life carried from the Earth. Another solution involves the use of huge orbiting mirrors, formed by thin films of alu- minated plastic materials, able to reflect the solar heat towards specific areas of the Mar- tian surface. There are also those who suggest carrying to Mars large amounts of ammonia, meth- ane and other molecules particularly suit- able for triggering a greenhouse effect, such as CFCs and PFCs. These molecules are much more efficient than CO 2 at promoting greenhouse behavior, but are also decidedly detrimental to the desirable formation of an ozone layer (similar to our terrestrial one), itself essential for reducing the flow of ultraviolet rays that sterilize the Martian surface. Whatever strategy was to be adopted to re- constitute the magnetic field and the at- mosphere, it would be effectively useless if there was not enough CO 2 on Mars to con- solidate the desired greenhouse effect. So far, scientists have been quite optimistic about the CO 2 content, but a very recent study, promoted by NASA and published at the end of July in Nature Astronomy, states exactly the opposite. The authors are Bruce M. Jakosky (Univer- sity of Colorado, Boulder) and Christopher S. Edwards (Northern Arizona University). In their article, entitled “Inventory of CO 2 available for terraforming Mars” , the two researchers examine data collected over the last two decades from various probes that have measured the abundances of CO 2 in the atmosphere, on the surface and in the subsoil of Mars, as well as the dispersion of atmospheric gases in space.