The terraforming of Mars is the process by which the climate and surface of Mars are deliberately changed with the goal of making it habitable by humans and other terrestrial life; and thus providing the possibility of safe and sustainable colonization of the large areas of the planet. Based on experiences with Earth, the environment of a planet can be altered deliberately and several of the methods described below have begun, but others are beyond our technical and economic resources.
Reasons for terraforming
In the not-too distant future, population growth and demand for resources may create pressure for humans to colonize new habitats such as the surface of the Earth's oceans, the sea floor, near-Earth orbital space, the moon and nearby planets, as well as mine the solar system for energy and materials[1]. Thinking far into the future (in the order of hundreds of millions of years), some scientists point out that the Sun will eventually grow too hot for Earth to sustain life, even before it becomes a red giant star, because all main sequence stars brighten slowly throughout their lifetimes. When this happens, it will become imperative for humans to migrate away to areas farther from the sun if they have any hope of surviving. Through terraforming, humans could make Mars habitable long before this 'deadline'. Mars could then be in the habitable zone for a while, giving humanity some thousand additional years to develop further space technology to settle on the outer rim of the solar system, before Mars becomes uninhabitable due to the sun's increasing heat.
[edit] Background
See also: Atmosphere of Mars
Mars consists of much of the soil minerals needed to terraform. Additionally recent scientific research has revealed there are large amounts of water locked up as ice permafrost just below the surface down to latitude 60, as well as at the surface on the poles where it is mixed with dry ice, frozen CO2. It is even suggested that there are vast amounts of ice in the deeper crust. As the polar carbon dioxide ice (CO2) sublimes back into the atmosphere during the martian summer, it leaves a small amounts of water residue, which fast winds sweep off the poles at speeds approaching 250 mph (400 km/h). These seasonal actions transport large amounts of dust and water vapor giving rise to Earth-like cirrus clouds.
Oxygen is present in the atmosphere only at trace amounts but it is found in large amounts bound to the highly oxidized metal-oxides on the Martian surface; some oxygen is also found in locked in the soil in the form of per-nitrates [2]. Analysis of soil samples taken by the Phoenix lander, indicate the presence of perchlorate. Perchlorates have been used to liberate oxygen in chemical oxygen generators. Additionally. Large amounts of oxygen are chemically locked up in water, which is present as ice in large amounts on Mars. Electrolysis could easily release the gas as long as there was a plentiful source of electrical energy. Hydrogen could also be produced this way.
It is generally thought that Mars could once have had an environment relatively similar to today's Earth, during an early stage in its development. This similarity is predominantly associated with the thickness of the atmosphere and the past presence of liquid water. Much of the atmosphere has been lost over millions of years although much has also been frozen as dry ice. Much of the water has just been frozen and still exists at the poles and just below the surface to latitude 60 as permafrost. The exact mechanisms which resulted in this change are still unclear, though several mechanisms have been proposed. For instance, the gravity of Mars today indicates that lighter gases in the upper atmosphere would have contributed to this loss, with the excess atoms dissipating into space. The lack of plate tectonics on Mars today and in the past, indicated by the thorough examination of its surface features is another plausible factor, since this would cause the recycling of gases locked up in sediments back into the atmosphere to occur at a slowed rate. The lack of magnetic field and geologic activity may both be a result of Mars' smaller size, which allows its interior to cool more quickly than Earth's, though the details of such processes are still not precisely clear. However, none of these processes are likely to be significant over the typical lifespan of most animal species, or even on the timescale of human civilization, and the slow loss of atmosphere could possibly be counteracted with ongoing low-level artificial maintenance activities.
[edit] Changes required
Terraforming Mars would entail two major interlaced changes: building up the atmosphere and keeping it warm. The atmosphere of Mars is relatively thin and thus has a very low surface pressure of 0.6 kPa, compared to Earth's 101.3 kPa. The atmosphere on Mars consists of 95% carbon dioxide (CO2), 3% nitrogen, 1.6% argon, and contains only traces of oxygen, water, and methane. Since its atmosphere consists mainly of CO2, a known greenhouse gas, once the planet begins to heat, more CO2 enters the atmosphere from the frozen reserves on the poles, adding to the greenhouse effect. This means that the two processes of building the atmosphere and heating it would augment one another, favoring terraforming. However, on a large scale, controlled application of certain techniques (explained below) over enough time to achieve sustainable changes, would be required to make this theory a reality.
Building the atmosphere
Chlorofluorocarbons (or CFCs) are the most likely candidates for artificial insertion into the Martian atmosphere because of their strong effect as a greenhouse gas. This can conceivably be done relatively cheaply by sending rockets with a payload of compressed CFCs on a collision course with Mars.[2] When the rocket crashes onto the surface it releases its payload into the atmosphere. A steady barrage of these "CFC rockets" would need to be sustained for a little more than a decade while the planet changes chemically and becomes warmer.
As the planet becomes warmer, the CO2 on the polar caps sublimes into the atmosphere and contributes to the warming effect. The tremendous air currents generated by the moving gasses would create large, sustained dust storms, which would also contribute to the warming of the planet by directly heating (through absorbing solar radiation) the molecules in the atmosphere. Eventually Mars would be warm enough that CO2 could not solidify on the poles, but liquid water would still not develop because the pressure would be too low.
After the heavy dust-storms subside, the warmer planet could conceivably be habitable to some forms of terrestrial life. Certain forms of algae and bacteria that are able to live in the Antarctic would be prime candidates. By filling a few rockets with algae spores and crashing them in the polar areas where there would still be water-ice, they could not only grow but even thrive in the no-competition, high-radiation, high CO2 environment.
If the algae are successful in propagating themselves around parts of the planet, this would have the effect of darkening the surface and reducing the albedo of the planet. By absorbing more sunlight, the ground will warm the atmosphere even more, and the atmosphere will have a new small oxygen contribution from the algae. This is still not enough oxygen for humans to breathe, but it's a step in the right direction.
Should the atmosphere grows denser, the atmospheric surface pressure may raise and approximate that of Earth. At first, until there is enough oxygen in the atmosphere, humans will probably need nothing more than a breathing mask and a small tank of oxygen that they carry around with them. To contribute to the oxygen content of the air, factories could be produced that reduce the metals in the soil, effectively resulting in desired crude metals and oxygen as a useful byproduct.
Also, by bringing plants with them (along with the microbial life inherent in fertile topsoil), humans could propagate plant life on Mars, which would ultimately create a sustainable oxygen supply to the atmosphere.
Another, more intricate method, uses ammonia as a powerful greenhouse gas (as it is possible that nature has stockpiled large amounts of it in frozen form on asteroidal objects orbiting in the outer solar system), it may be possible to move these (for example, by using very large nuclear bombs to blast them in the right direction) and send them into Mars's atmosphere. Since ammonia (NH3) is high in nitrogen it might also take care of the problem of needing a buffer gas in the atmosphere. Sustained smaller impacts will also contribute to increases in the temperature and mass of the atmosphere.
The need for a buffer gas is a challenge that will face any potential atmosphere builders. On Earth, nitrogen is the primary atmospheric component making up 77% of the atmosphere. Mars would require a similar buffer gas component although not necessarily as much. Still, obtaining significant quantities of nitrogen, argon or some other comparatively inert gas could prove difficult.
Hydrogen importation could also be done for atmospheric and hydrospheric engineering. Depending on the level of carbon dioxide in the atmosphere, importation and reaction of hydrogen would produce heat, water and graphite via the Bosch reaction.
Adding water and heat to the environment will be key to making the dry, cold world suitable for life. Alternatively, reacting hydrogen with the carbon dioxide atmosphere via the Sabatier reaction would yield methane and water. The methane could be vented into the atmosphere where it would act to compound the greenhouse effect.
Adding heat
Adding heat and conserving heat present is a particularly important stage of this process, as heat from the Sun is the primary driver of planetary climate. Mirrors made of thin aluminized PET film could be placed in orbit around Mars to increase the total insolation it receives.[3] This would direct the sunlight onto the surface and could increase the planet's surface temperature directly. The mirror could be positioned as a statite, using its effectiveness as a solar sail to orbit in a stationary position relative to Mars, near the poles, to sublimate the CO2 ice sheet and contribute to the warming greenhouse effect.
Since long term climate stability would be required for sustaining a human population, the use of especially powerful greenhouse gases possibly including halocarbons such as CFCs and PFCs. A proposal to mine fluorine-containing minerals as a source of these gases is supported by the belief that since the quantities present are expected to be at least as common on Mars as on Earth, this process could sustain the production of sufficient quantities of optimal greenhouse compounds (CF3SCF3, CF3OCF2OCF3, CF3SCF2SCF3, CF3OCF2NFCF3) to maintain Mars at 'comfortable' temperatures, as a method of maintaining an Earth-like atmosphere produced previously by some other means.[4]
Changing the albedo of the Martian surface would also make more efficient use of incoming sunlight.[5] Altering the color of the surface with dark dust and soot (likely from both of Mars' moons, Phobos and Deimos, because they are dark in color and could be ground into dust while in space and then somewhat uniformly distributed across the Martian surface by "dropping" it onto Mars), dark microbial life forms such as lichens would transfer a larger amount of incoming solar radiation to the surface as heat before it is reflected off into space again. Using life forms is particularly attractive since they could propagate themselves.
Another way to increase the temperature could be to direct small cosmic bodies (asteroids) onto the Martian surface; the impact energy would be released as heat and could evaporate Martian water ice to steam, which too is a greenhouse gas.
Dealing with solar radiation
It is believed by some that Mars would be uninhabitable to most life-forms due to higher solar radiation levels. Without a magnetosphere, the sun is thought to have thinned the Martian atmosphere to its current state; the solar wind adding a significant amount of energy to the atmosphere's top layers which enables the atmospheric particles to reach escape velocity and leave Mars (effectively boiling off the atmosphere). Indeed, this effect has even been detected by Mars-orbiting probes. Venus, however, shows that the lack of a magnetosphere does not preclude a dense atmosphere. A thick atmosphere could also provide solar radiation protection to the surface, as it does at Earth's polar regions where aurorae form, so the lack of a magnetosphere probably would not seriously impact the habitability of a terraformed Mars. In the past, Earth has regularly had periods where the magnetosphere changed direction and collapsed for some time.[citation needed] Some scientists believe that in the ionosphere a magnetic shielding was created almost instantly after the magnetosphere collapsed, a principle that applies to Venus as well and may also be the case in every other planet or moon with a large enough atmosphere.
References
^ Savage, Marshall T., The Millennial Project: Colonizing the Galaxy in Eight Easy Steps (Little Brown and Company, 1994)
^ a b Lovelock, James and Allaby, Michael The Greening of Mars
^ Robert M. Zubrin (Pioneer Astronautics), Christopher P. McKay. NASA Ames Research Center (1993?). "Technological Requirements for Terraforming Mars".
^ "Keeping Mars warm with new super greenhouse gases".
^ Peter Ahrens. "The Terraformation of Worlds" (PDF). Nexial Quest.
Links
NASA - Aerospace Scholars: Terraforming Mars
Recent Arthur C Clarke interview mentions terraforming
Red Colony
Terraformers Society of Canada
Research Paper: Technological Requirements for Terraforming Mars
Peter Ahrens The Terraformation of Worlds
MARSDRIVE: Colonizing Mars. Red Colony parent organization planning the future exploration and colonization of planet Mars.
Mars Reborn, a portrait of a possible Mars one thousand years from now, by Chris Wayan, 2003
Total Recall, an American science fiction film from 1990; an example of popular culture speculation regarding the terraforming of Mars.
Mars trilogy, a science fiction trilogy of novels by Kim Stanley Robinson which goes into great depth about possible terraforming techniques and the consequences resulting.
