Terraforming, or “earth-shaping,” is the process of changing various elements of another planet or moon’s environment to more closely resemble that of earth’s. Specific focus is centered on the manipulation of atmosphere, temperature, surface topography, and ecology, and the end goal is to create a world that is habitable for humans.
The term seems to be first used by author Jack Williamson in his story “Collision Orbit,” published in 1942. Since then, it has been the subject of science fiction books and movies, but has made its way into respected scientific inquiry, and has even been the topic of numerous NASA-hosted debates.
Terraforming first entered the scientific arena in 1961, when Carl Sagan submitted an article to the journal, Science, outlining a proposed method for altering Venus’ atmosphere by seeding it with algae. He reasoned that the algae would make organic compounds out of the water, nitrogen, and carbon dioxide that are present. The idea was ground-breaking, but further discoveries about Venus’ atmosphere (including the fact that it contains clouds of highly-concentrated sulfuric acid) made this method impossible. In 1973, Sagan submitted another article, titled “Planetary Engineering on Mars,” which seemed more promising. NASA ran with the ideas outlined in his article, and three years later, concluded that it was possible to make Mars into a habitable planet. At this point, the idea exploded, both in scientific and popular literature. So far, the costs required to undertake any sort of terraforming have been completely prohibitive, but the scientific principles behind it remain relatively sound.
We have a pretty good understanding of the elements humans need to survive, because it’s easy to study our own biosphere. Earth’s atmosphere is made up of 78.1% Nitrogen, 20.9% Oxygen, 0.9% Argon, and 0.1% Carbon Dioxide and other gases. We have extended regions of liquid water, a viable energy source in the sun, and protection from solar radiation thanks to our atmosphere and magnetosphere. In order to survive elsewhere, we need to replicate these conditions as closely as possible, and we need to create a system where these conditions are sustained over a long period of time.
At this point, our sights are aimed at Mars. It’s relatively close, seems to have at least some water frozen at its poles, and may have even supported life in the distant past. However, Mars presents a great deal of significant challenges before it could support even basic forms of life.
Temperature, Air Pressure, and Atmospheric Composition
The most vital parameters that need to be changed in order to successfully terraform Mars are temperature, air pressure, and atmospheric composition. Thankfully, these three parameters are tethered to each other, and thus, a change in one will help move the others in a beneficial direction.
Mars’ surface temperature ranges between 81 F and -225 F, with an average around -67 F. Obviously, we’ll need to heat Mars up in order to sustain life as we know it. Mars is cold for a couple reasons – number one being that it is farther away from the sun than earth (a full 50% farther). Secondly, Mars’ atmosphere is thin, so it can’t trap much of the solar energy that does reach its surface.
Mars’ atmospheric pressure averages 600 Pa, compared to Earth’s average atmospheric pressure of 101,000 Pa. As such, even if the temperature on Mars reaches above freezing, ice won’t melt because it remains below its triple point (look up your chemistry!). Instead, it sublimates – turns directly from a solid into a gas. In a couple places at the bottom of huge depressions on Mars’ surface, where atmospheric pressure increases to 1155 Pa, liquid water can be made, but this is rare.
Currently, Mars’ atmosphere consist largely of carbon dioxide (95.3%, compared to 0.1% here on Earth). It contains only 2.7 % Nitrogen, and 0.2% Oxygen. Interestingly, Mars’ current atmospheric conditions are very similar to the atmosphere of early Earth. Of course this begs the question, “Can we transform Mars’ atmosphere following Earth’s example?” So far, scientists think the answer is, “yes, ” and a number of ideas have been floated so far:
1. Orbiting mirrors
The idea: Station a gigantic mirror such that it reflects the sun’s light onto one of Mars’ poles and heating up the surface so that CO2 is released into the atmosphere.
There is presently enough carbon dioxide (CO2) as ice in the Martian south pole and absorbed by regolith (soil) around the planet that, if sublimated to gas by a climate warming of only a few degrees, would increase the atmospheric pressure to 300 millibars, comparable to twice the altitude of the peak of Mount Everest. While this would not be comfortably breathable by humans, it would eliminate the present need for pressure suits, melt the water ice at Mars’s north pole (flooding the northern basin), and bring the year-round climate above freezing over approximately half of Mars’s surface.
2. Kamikaze asteroids
The idea: Send asteroids ripe with ammonia and nitrogen hurling into Mars to create a runaway greenhouse effect.
Another, more intricate, method uses ammonia as a powerful greenhouse gas (as it is possible that large amounts of it exist in frozen form on asteroidal objects orbiting in the outer Solar System); it may be possible to move these (for example, by using nuclear bombs to blast them in the right direction) and send them into Mars’s atmosphere. Sustained smaller impacts will also contribute to increases in the temperature and mass of the atmosphere.
3. Huge halocarbon factories
The idea: Establish factories on Mars that produce large amounts of halocarbons, again resulting in a runaway greenhouse effect.
This would be nearly impossible, given the extreme energy requirement, and need for 1000’s of people to keep the plants running.
4. Clouds of darkness
The idea: Spread dust into Mars’ atmosphere, darkening the planet so that it can absorb more light and thus, more heat
Reducing the albedo of the Martian surface would make more efficient use of incoming sunlight. This could be done by spreading dark dust from Mars’s moons, Phobos and Deimos, which are among the blackest bodies in the Solar System; or by introducing dark extremophile microbial life forms such as lichens, algae and bacteria. The ground would then absorb more sunlight, warming the atmosphere.
After we’ve increased Mars’ temperature, atmospheric pressure, and altered its atmospheric make-up, we need to start depending on biology to help us out. Primitive plants (algae, plankton, etc…) can turn atmospheric CO2 into oxygen, and plankton can turn dissolved CO2 into oxygen. As the oxygen levels start to rise, we can introduce more complex plant life that requires at least some oxygen to survive (grasses, trees, etc…). Of course, once we have abundant plant life, animals are next…
If algae or other green life were established, it would also contribute a small amount of oxygen to the atmosphere, though not enough to allow humans to breathe. On 26 April 2012, scientists reported that lichen survived and showed remarkable results on the adaptation capacity of photosynthetic activity within the simulation time of 34 days under Martian conditions in the Mars Simulation Laboratory (MSL) maintained by the German Aerospace Center (DLR).
The biggest issue facing our terraforming project is Mars’ near lack of a magnetic field. Without a strong magnetic field, solar winds will literally blow away an atmosphere over hundreds of thousands of years (this may be what happened to Mars in the first place). A magnetic field is also instrumental in deflecting UV radiation, which is lethal to nearly all forms of life. A thick atmosphere does a pretty good job of shielding UV radiation, but even if we put our own atmosphere on Mars, we would still be facing excess amounts of UV radiation.
How long would it take?
With current technology, our timeline looks like this:
Colonization and/or construction of mirrors = 100 years from now
Warming to the point that CO2 releases = 200 years from now
Seeding of microbes = 25-50 years
Oxygen production to levels breathable by humans = 40,000 years.