It’s one idea to have astronauts stay in life-support domes on the Martian surface; it’s another to transform the entire planet into a habitable paradise. The fantasy of terraforming Mars has been prominent for a long, long time. The prospect permeates media, from sci-fi novels like Arthur C. Clarke’s The Sands of Mars in 1951 to modern films like 2015’s The Martian. At first glance, the idea seems entirely fanciful, but scientists have actually developed a few theoretical methods of terraformation over the years. Even though the undertaking would be an unrealistically expensive and energy consumptive endeavour as of now, perhaps it is a future that humanity can one day claim as its own.
The Red Planet is the best candidate for colonization in our solar system, but that’s not saying much. When our other terrestrial planets include a sulphurous, suffocating ball of heat and pressure or an atmosphere-less planet with midday temperatures of around 400°C and cool, breezy evenings at -173°C, there isn’t much competition. But even though Mars has a leg up in the atmospheric sense, it is still frightfully thin with a composition unfavourable to human life. Its atmosphere is 1% the thickness and 0.6% of the pressure of Earth’s and is 95.32% carbon dioxide. Additionally, the lack of an ozone layer and magnetosphere mean that radiation is constantly bombarding the surface. While the average daily temperature in the summer can reach up to 20°C, nights can plummet to a deadly -73°C due to lack of insulation from the atmosphere. Martian soil isn’t very friendly either. Perchlorates widespread on the surface become deadly to even the most resilient bacteria when ionized by the presence of UV radiation, as seen in a study published by Nature on July 6, 2017. Despite these biological obstacles, most ideas surrounding terraformation start at the basics and tend to stick to the more physical barriers such as raising the temperature, thickening the atmosphere, and lessening radiation. Four different propositions are going to be discussed: lowering the albedo of the surface, introducing greenhouse gases, implementing orbiting mirrors, and creating an artificial magnetosphere.
One of the first proposed methods of terraformation came from the legendary astrophysicist himself, Carl Sagan, in his article “Planetary Engineering on Mars” published July 20, 1973. The paper suggests that if 5-8% of the polar ice caps of Mars were covered in 1 millimeter of material with an albedo below 0.25, the caps would increase in temperature which in turn would bump up the atmospheric pressure and therefore increase advective heat transport (heat transport through bulk flow of fluid) between the caps and equator so the cycle of heating would then sustain itself. Ideally, this would bring the planet to a more comfortable temperature. However, it was recognized that the weight of material required to do so would be approximately 108 metric tons. Even though it’s almost 50 years later, this weight remains an unviable number. In fact, as of 2017, the largest payload in a rocket still goes to Saturn V which was launched in the 1960s. Though space technology has been advancing at an incredible rate, certain things just haven’t been achieved, and this is one of them. Interestingly, Sagan spun this limitation in a positive light in his article: “This is probably all to the good : it is obviously unwise to perform a major alteration in a planetary environment before that planet has been thoroughly explored.” Fair enough, Carl Sagan, fair enough. At least as of now, there is no need to subject yet another planet to the whims of humanity, especially since there is so much precious information waiting to be unlocked, sans-human interference, like whether or not life was ever present in Mars’s ancient oceans. Just as the “prime directive” instructs, humanity has so far done its best to prevent contaminating astronomical objects with our life before we can detect any of their own. On that note, what boundaries would the complete terraformation of Mars cross? Part of the reason human habitation is such an exciting idea is because of what could be learned from us being there. Robots controlled by scientists hundreds of millions of kilometres away have far more limitations than scientists acting on site. But what is the distinction between the growth of humanity and the destruction of Mars’ scientific past, present, and future? Where do we draw the line?
If we are to put aside philosophical conundrums for a moment and focus again on the logistics, another proposed approach to terraformation is installing orbital mirrors around the Red Planet to direct certain wavelengths of light onto the surface. The research paper “Technological Requirements for Terraforming Mars” suggests that warming a few specific spots on the planet by just 5°C would be sufficient to jumpstart the terraformation process. A mirror with a radius of 125 km could theoretically heat up “the entire area south of 70 degrees south latitude by 5°C”. The engineering of such a mirror would be highly implausible if launched from here on earth given that the device would have a mass around 200,000 metric tons (this assumes it is made out of aluminized mylar material). However, materials from asteroids, Mars, or the Moon in conjunction with manufacturing in space would be a more viable option. The researchers also calculated that processing the materials would require approximately 120MW-years worth of energy which could be provided by nuclear reactors similar to what are being used in nuclear electric spacecraft.
The primary purpose of these mirrors would be to melt the carbon dioxide ice composing the tops of the polar ice caps to increase atmospheric pressure and enhance the concentration of greenhouse gases in the atmosphere. As the planet warmed, carbon dioxide stores within the planet’s crust would also evaporate into the atmosphere to continue the cycle. This would need to be implemented in combination with other gases. Other proposals include the manufacturing of CFCs from factories on Mars and importing gases such as ammonia and methane from Earth or nearby asteroids. Though not as potent as super greenhouse gases like chlorofluorocarbons, these gases would have a more intense greenhouse effect than carbon dioxide alone and would speed up the warming process.
As previously mentioned, a phenomenon that has started to become detrimental to life here on Earth could be Mars’s saving grace; the greenhouse effect. Many studies and simulations have suggested ‘injecting’ the Martian atmosphere with heat-absorbing gases could increase the temperature and atmospheric pressure in order to sublimate the carbon dioxide from the ice caps, melt the water to form an ocean, and maintain a temperature suitable for human life. One such study is called “Keeping Mars warm with new super greenhouse gases” published January 11, 2001. The primary gases of choice are chlorofluorocarbons (CFCs), which would be manufactured from fluorine mined locally instead of from Mars itself since it is unknown whether it exists on the planet in sufficient quantities. This is because CFCs are some of the most powerful greenhouse gases, especially in comparison to naturally occurring gases like carbon dioxide and methane. Some gases in consideration can be seen in Table 1 (below).
The catalyzation of the warming and sublimation of the ice caps remains the most difficult problem to resolve, which could be solved using the aforementioned solar sail method. On the other hand, maintaining Earth-like temperatures would be relatively easy in comparison. The study suggests that the GHGs would need to be replenished with 170-400 kilotons every year year in order to account for loss of gas, mostly due to photolysis (decomposition due to light). Other contributions to gas loss include chemical reaction with oxygen in the atmosphere, however, this decrease is less significant than photolysis. The volume of here on Earth would not pose an issue. However, similar to the transport of low-albedo material, the sheer weight of the load makes this currently implausible.
The last three proposed terraformation methods focused almost entirely on raising the temperature of the planet. However, that alone would not be enough to sustain life. As many of you may have been thinking, the introduction of heat alone would not be sufficient if the atmosphere is not thick enough to keep it in and the ‘injection’ of GHGs into the atmosphere could end up being futile due to the relatively high rate of atmospheric escape from solar wind. One method that could counteract many of these concerns was proposed in the article “A Future Mars Environment for Science and Exploration” published this year. This paper proposes that the implementation of an artificial magnetosphere to protect Mars from solar radiation would be enough to retain the atmosphere, increase atmospheric pressure, warm the planet, melt the icecaps, and so on. Mars lost its own magnetic field more than three billion years ago which meant that its atmosphere was slowly driven away as ions from solar winds bombarded the atmosphere and caused gas to escape. It’s theorized that the reduced pressure, among other factors, caused much of the water ocean (which may have covered 30% of the Martian surface) to evaporate. Since almost 1/7th of the ancient Martian ocean is estimated to be trapped in the ice caps and an increase of 4-5°C is deemed sufficient to begin the melting process, the installation of an artificial magnetic field could essentially ‘reverse’ this event. A magnetic dipole of 102 Teslas at Mars L1 Lagrange point could be generated so that the magnetotail protects the planet, especially the two major escape channels for charged particles - the northern polar ice cap and the equatorial zone. The article suggests the use of simulations to emulate Mars’s atmosphere and determine the best ways to prevent the solar wind from stripping away the atmosphere.
If these strategies were ever to be implemented, one alone would not likely be enough. Instead, a combination of some (or even all) of these methods could be used to heat up the planet, melt the polar ice caps, increase atmospheric pressure, and create a self-sustaining world with a liquid water ocean and warm temperatures. Though the ideas discussed are entirely theoretical, perhaps one day we will possess the technology and funds to make Mars our own.
Sagan, Carl. “Planetary Engineering on Mars.” Icarus, vol. 20, no. 4, 1973, pp. 513–514., doi:10.1016/0019-1035(73)90026-2. Zubrin, Robert, and Christopher Mckay. “Technological requirements for terraforming Mars.” 29th Joint Propulsion Conference and Exhibit, 1993. http://www.users.globalnet.co.uk/~mfogg/zubrin.htm
Gerstell, M. F., et al. “Keeping Mars warm with new super greenhouse gases.” Proceedings of the National Academy of Sciences, vol. 98, no. 5, 2001, pp. 2154–2157., http://www.pnas.org/content/98/5/2154.full.pdf.
A FUTURE MARS ENVIRONMENT FOR SCIENCE AND EXPLORATION. J. L. Green1 , J. Hollingsworth2 , D. Brain3 , V. Airapetian4 , A. Glocer4 , A. Pulkkinen4 , C. Dong5 and R. Bamford6 ( 1 NASA HQ, 2 ARC, 3 U of Colorado, 4 GSFC, 5 Princeton University, 6 Rutherford Appleton Laboratory) https://www.hou.usra.edu/meetings/V2050/pdf/8250.pdf