Terraforming is the process of creating a habitable environment on another planet, artificially. The term first came up in Jack Williamson’s short story Collision Orbit. However, the concept has been around from long before Jack Williamson. Many science fiction writers have explored aspects of terraforming – positive as well as negative. 

Books such as The Last Judgement, Depths of Time, Farmer in The Sky, The Snows of Ganymede brought terraforming into popular culture. The first book based on the concept was The Sands of Mars by the reputed science fiction author – Arthur C. Clarke. It involved Mars settlers warming up the planet by converting its moon Phobos into a second sun. Other books such as The Greening of Mars offered a scientific basis that allowed readers to visualise terraforming as a blend of fiction and proven facts.

Terraforming has also featured in the popular Star Trek series and other films like Total Recall and Aliens. Video games like SimEarth, SimLife, SimMars, Master of Orion etc. are based entirely on the concept of terraforming.  

The first scientist to suggest terraforming was the legendary Carl Sagan. He suggested terraforming Venus and Mars, the two planets closest to us in the habitable zone. Even today, some scientists advocate terraforming as the optimum way to colonise Mars. However, challenges to terraforming are immense, without considering the shortage of economic and natural resources.

Here are some features of the Martian environment that terraforming seeks to amend:

1. Low atmospheric pressures, below the Armstrong limit
2. No shielding against solar and cosmic radiation and solar winds
3. Atmosphere composition that is not suitable for life
4. Unavailability of liquid water
5. No food source
6. Instability of organic compounds
7. Destructive dust storms
8. Weak surface gravitational acceleration

The Three Fundamental Challenges

Low atmospheric pressure 

Perhaps the chief reason that makes Mars uninhabitable. Currently, the atmospheric pressure at the Martian surface is around 1kPa – while we walk around on another at around 100kPa. Due to low pressures, water cannot be retained in its liquid state. The atmospheric pressure levels are well below the Armstrong limit, which means, even with an abundance of oxygen, humans wouldn’t be able to survive on the surface of Mars for more than a few minutes. 

Low gravity

Mars has about 38% of the Earth’s surface. If we decided to increase the atmospheric pressure by increasing the density of the atmosphere, we would need 2.6 times the air mass of the earth to bring pressure to the optimal 100kPa. 

Effects of Cosmic Weather

Mars has no intrinsic magnetic field. This causes the formation of a magnetosphere due to the interaction of solar winds with the atmosphere. Thus solar radiation cannot be mitigated. The solar winds ionise the atmosphere, which causes issues in Mars retaining the atmosphere. It also prohibits any liquid water on the surface from being retained.

Proposed methods and Feasibility

Terraforming Mars would begin with three primary interlaced changes. Modifying the atmosphere, building up the magnetosphere and increasing the ambient temperature are changes necessary for any life to survive on the planet. Modifying the atmospheric composition to increase the greenhouse effect will lead to a rise in temperature. This rise in temperature will, in turn, melt the polar ice caps, increasing the carbon dioxide in the atmosphere. Building up the magnetosphere will prevent the ejection of the atmosphere from the planet. Thus these three changes augment each other. 

Thickening the atmosphere

In order to thicken the atmosphere, it is necessary to either import them or release them from the planet itself. Currently, the atmosphere on Mars predominantly consists of carbon dioxide. Compounds found on the surface of Mars can be decomposed to release gases in order to thicken the atmosphere.   

Carbon Dioxide

Carbon dioxide and water vapour are the only gases present on the surface of Mars to provide significant global warming effects. Both of these can be found in frozen form at the poles of Mars. However, the carbon dioxide in frozen is only 0.6% of the total amount required to increase the atmospheric pressure to the levels of earth.  Other carbon dioxide sources include clathrate compounds (0.5%), minerals (1.2%) and adsorbed carbon dioxide (4%). Combining all these sources can only raise the pressure to 1.2 kPa of the optimum 100 kPa. All these figures are sourced from 20 years’ worth of data collected by NASA. However additional data may provide new conclusions.

Water vapour is another component that could lead to the greenhouse effect. However, the conditions of temperature and pressure are such that water cannot exist in vapour form for long without freezing. It needs to be heated considerably before it can contribute effectively to the atmosphere.

Ammonia

Scientists have considered importing ammonia, a powerful greenhouse gas from asteroids. This scheme is farfetched, as it would involve redirecting suitable asteroids towards Mars. Even if this was successful, ammonia would not be stable in the Martian environment. Also, ammonia is a light gas, about one fifth the density of nitrogen. This implies that the ammonia which would not decompose would be lost into space due to low gravity.  

Fluorine compounds

Fluorine bearing compounds make for powerful greenhouse gases. These include hexafluorides, halofluorides and chlorofluorocarbons. Relatively stable, they can be released on the planet using rockets with payloads of compressed gases. Such rockets would have to be sent continually for over a decade for sufficient changes to occur. This may sound technologically plausible but has economic constraints. In order to make the frozen carbon dioxide on Mars sublime, about 39 million tonnes of CFCs would be required. This is three times the amount produced on earth in 20 years. Also, to make up for the losses to space and photolysis, about 170 thousand tonnes of CFCs, would have to be sent annually. Those in support of terraforming suggest mining of fluorine-containing minerals from Mars in order to maintain the temperatures created initially.

Others

Minerals such as per-nitrates and perchlorates have been found on Mars which can be used to release oxygen into the Martian atmosphere. However, these are not to be found in sufficient quantities to maintain Earth-like temperatures.

Increasing the ambient temperature

Orbital Mirrors

Scientists have proposed using reflective aluminium films in order to heat Mars directly. These would be stationary with respect to the planet at the poles. This should cause the polar carbon dioxide to sublime and contribute toward the warming of Mars.

Albedo reduction

One way to increase the temperature of Mars would be to make its surface more absorptive toward sunlight. This can be achieved by spreading dark dust, likely from its moon Phobos, on the Martian surface. It can also be achieved by growing dark coloured extremophile algae or lichen on the surface of Mars. However, Mars already absorbs 70% of incoming sunlight. Thus these methods would not contribute significantly to warming the planet.  Another problem is the global dust storms cover the planet blocking the sun and causing drastic fall in surface temperature.

Retaining the atmosphere

The solar winds interact with the Martian atmosphere causing it to eject its contents into space. Preventing this would be a major step in terraforming Mars. It should protect current as well as any future artificial build-up of the atmosphere.  The best way to accomplish this would be to induce a magnetic field around the planet artificially.

Superconducting rings (SMEs)

Japanese scientists have suggested that it is possible to build a magnetic field around Mars with existing technology. Their paper suggests latitudinal superconducting rings. These would have to be appropriately refrigerated and supplied with D.C. current. They have also emphasised the fact that this scheme is not beyond the economic restraints.

Magnetic shields on L1 orbit

NASA scientist Jim Green has proposed a magnetic dipole shield between the Sun and Mars to protect it from solar winds. He suggests that this can be achieved by a magnet of around 2 Tesla at Langrange or L1 point. This would allow Mars to retain its atmosphere. It could achieve about half the atmospheric pressure of the earth in a few years.  

Current Developments 

NASA quite recently admitted that our current technology is not capable of terraforming Mars. This isn’t surprising, but creating magnetic shields remains the easiest step towards terraforming. NASA however, has a project lined up for Mars. Since 2014, NASA and Techshot Inc. have been working on Ecopoiesis for Mars– it involves sending sealed biodomes to Mars. These biodomes would contain oxygen-producing algae and lichen. They would be initially tested on a small scale. NASA plans to send small canisters of the extremophile lichen with its next rover mission. The rover would then observe the lichen and the oxygen produced. If this experiment is successful, the NASA plans to build larger, sealed environments to grow this lichen. It would provide oxygen as well as a support system for future manned missions.

Elon Musk has spoken about his dream to achieve terraforming on Mars. He has elaborated about building artificial ‘suns’ to heat the planet. Musk also suggested hitting the poles of Mars with nuclear weapons. He has dismissed the findings of NASA as inaccurate. 

Musk plans to send two rockets to Mars with supplies. These are a part of the mission taking place in 2024. In 2024 Elon Musk plans to send four more rockets to Mars, two of which will be manned. He claims that SpaceX could set up a colony within the next decade.

Conclusion

With limited data and only theory for a project of this magnitude, it is difficult to predict the direction we’d go and how long we’d take. The challenges for terraforming Mars are, of course, immense. Political and economic factors will also play a major role in terraforming Mars. But it’s safe to assume a life-supporting environment could be achieved by terraforming Mars by the end of the century.