Terraforming Celestial Bodies For Human Life: Mars Case Study
Manned galactic space travel, coupled with a population likely too large for the Earth, will inadvertently lead to human colonization of different planets and moons. The construction of safe indoor and outdoor living spaces on other planets requires changing the ecology and atmosphere of the planet to be friendly towards the species of Earth. It takes a monumental engineering effort for a planet to become habitable enough for an astronaut to land and be able to safely take off their spacesuit. Since the most viable planet closest to us is Mars, most ecopoiesis/terraforming research efforts are being directed there.
The first phase in making a planet hospitable to the human race is ecopoiesis, where an ecosystem is artificially constructed to begin altering the planet i.e. its atmosphere. The oxygen requirement for human life is nearly nonexistent, so photosynthesis is needed to transform the carbon dioxide of Mars (Thomas 1995). Earth plant life has a minimum requirement of about 10mbar of nitrogen, however, which would first need to be produced by Earth bacteria through denitrification (McKay et al. 1991, Friedman et al. 1995). Because of this, the first step in transforming the biosphere of Mars is to introduce large amounts of nitrogen-releasing bacteria to martian soil (Friedmann et al. 1995).
Once the atmosphere has enough nitrogen in it, plants engineered to survive on as low as 1mbar of oxygen can get to work on converting the massive amounts of carbon dioxide in the atmosphere – there is no observable limit to the maximum concentration of carbon dioxide conducive to Earth plant life. Sending species heavily resistant to UV damage would lead to the best results, as Mars has no ozone layer (Thomas 1995).
The resulting engineered atmosphere will still be too light for human life – the average pressure of Mars’s atmosphere is 6-10mbar while one Earth atmosphere is defined as 1bar. CFCs and other greenhouse gases are being considered as candidates for increasing the thickness of the martian atmosphere to weights friendly to humans. The increase of atmospheric density would also lead to the increase of global temperatures – the average martian surface temperature is -60 Celsius and would ideally need to rise at least 60 degrees to allow for liquid water (Budzik 2000). The increasing temperatures caused from the release of greenhouse gases would lead to the polar caps melting and heating the atmosphere even further in a positive feedback loop (McKay et al. 1991). Budzik claims that an initial increase of 4 degrees Celsius will result in a total increase of 55 degrees (Budzik 2000).
A very careful balance must be struck between the concentrations of the various gases in the newly engineered atmosphere to safely recreate the Earth’s atmosphere. A detailed breakdown of concentrations is provided by McKay et al. in Figure 1:
Figure 1. Atmospheric gas limits for sustainable human life retrieved from McKay et al. 1991
This transformation process of gas ratios is very lengthy and convoluted. Birch proposed an alternative method of evaporating the polar caps by using a giant (200,000 ton) mirror to redirect sunlight towards them (Budzik 2000, Birch 1992). Other more immediate methods include dropping bombs or redirecting asteroids to kick up large amounts of dust and make the atmosphere heavier (Budzik 2000).
The methods presented here can be adapted for barren dusty planets with polar caps. As we have not yet tried expanding to planets hotter than our own (e.g. Venus), we have not yet developed methods for terraforming these types of bodies. Although some planets may be completely uninhabitable, it is likely that the astronauts of the far distant future will be able to transform the vast majority of celestial bodies.
References:
Budzik JM. 2000. How to Terraform Mars: An Analysis of Ecopoiesis and Terraforming Research 1:17
Thomas DJ. 1995. Biological Aspects of the Ecopoiesis and Terraformation of Mars: Current Perspectives and Research 415:418
McKay CP, Toon OB, Kasting JF. 1991. Making Mars Habitable 489:496
Friedmann EI, Ocampo-Friedmann R. 1995. Advances in Space Research 243:246
Birch P. 1992. Terraforming Mars quickly Abstract
