Space-Terraforming

If a viable Martian civilization can be established, its population and powers to change its planet will continue to grow. The advantages accruing to such a society of terraforming Mars into a more human-friendly environment are manifest4. Put simply, if enough people find a way to live and prosper on Mars there is no doubt but that sooner or later they will terraform the planet. The feasibility or lack thereof of terraforming Mars is thus in a sense a corollary to the economic viability of the Martian colonization effort.

Potential methods of terraforming Mars have been discussed in a number of locations.5,6. In the primary scenario, artificial greenhouse gases such as halocarbons are produced on Mars and released into the atmosphere. The temperature rise induced by the presence of these gases causes CO2 adsorbed in the regolith to be outgassed, increasing the greenhouse effect still more, causing more outgassing, etc. In reference 6 it was shown that a rate of halocarbon production of about 1000 tonnes per hour would directly induce a temperature rise of about 10 K on Mars, and that the outgassing of CO2 caused by this direct forcing would likely raise the average temperature on Mars by 40 to 50 K, resulting in a Mars with a surface pressure over 200 mbar and seasonal incidence of liquid water in the warmest parts of the planet. Production of halocarbons at this rate would require an industrial establishment on Mars wielding about 5000 MW or power supported by a division of labor requiring at least (assuming optimistic application of robotics) 10,000 people. Such an operation would be enormous compared to our current space efforts, but very small compared to the overall human economic effort even at present. It is therefore anticipated that such efforts could commence as early as the mid 21st Century, with a substantial amount of the outgassing following on a time scale of a few decades. While humans could not breath the atmosphere of such a Mars, plants could, and under such conditions increasingly complex types of pioneering vegetation could be disseminated to create soil, oxygen, and ultimately the foundation for a thriving ecosphere on Mars. The presence of substantial pressure, even of an unbreathable atmosphere, would greatly benefit human settlers as only simple breathing gear and warm clothes (i.e. no spacesuits) would be required to operate in the open, and city-sized inflatable structures could be erected (since there would be no pressure differential with the outside world) that could house very large settlements in an open-air shirt-sleeve environment.

Nevertheless, Mars will not be considered fully terraformed until its air is breathable by humans. Assuming complete coverage of the planet with photosynthetic plants, it would take about a millennia to put the 120 mbar of oxygen in Mars' atmosphere needed to support human respiration in the open. It is therefore anticipated that human terraformers would accelerate the oxygenation process by artificial technological approaches yet to be determined, with the two leading concepts being those based on either macroengineering (i.e. direct employment of very large scale energy systems such as terrawatt sized fusion reactors, huge space-based reflectors or lasers, etc.) or self reproducing machines, such as Turing machines or nanotechnology. Since such systems are well outside current engineering knowledge it is difficult to provide any useful estimate of how quickly they could complete the terraforming job. However in the case of self-replicating machines the ultimate source of power would be solar, and this provides the basis for an upper bound to system performance. Assuming the whole planet is covered with machines converting sunlight to electricity at 30% efficiency, and all this energy is applied to releasing oxygen from metallic oxides, a 120 mbar oxygen atmosphere could be created in about 30 years.