Terraforming of Mars

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Artist's conception of the process of terraforming Mars; the final appearance of the planet is based on data from the Mars Global Surveyor.

The terraforming of Mars is the hypothetical process by which the climate, surface and known properties of Mars would be 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; however the feasibility of creating an unconstrained planetary biosphere is undetermined. Several of the methods described below may fall within humanity's technological capabilities, but at present the economic resources required to execute such methods are far beyond that which any government or society is willing to allocate to such a purpose.


[edit] 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 we 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 thousands of 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

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 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 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.

[edit] Building the atmosphere

Artist's conception of a terraformed Mars centered on the Tharsis region.

The main way to build the martian atmosphere is importation of water, that can be obtained, for example, from ice asteroids or from ice moons of Jupiter or Saturn. Adding water and heat to the environment will be key to making the dry, cold world suitable for life.

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.[citation needed] Alternatively, reacting hydrogen with the carbon dioxide atmosphere via the Sabatier reaction would yield methane and water.[citation needed] Another way is importation of methane or other hydrocarbons, that are usual in Titan's atmosphere. The methane could be vented into the atmosphere where it would act to compound the greenhouse effect.

Methane (or other hydrocarbons) also can be helpful to produce a quick increase for the insufficient martian atmospheric pressure. Also, these gases can be used for production (at the next step of terraforming of Mars) of water and CO2 for martian atmosphere, by reaction:

CH4 + 4 Fe2O3 => CO2 + 2 H2O + 8 FeO

Probably, this reaction may be initiated by heat or by martian solar UV-irradiation. Large amounts of the resulting products (CO2 and water) are necessary to initiate the photosynthetic processes.

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. If the atmosphere grows denser, the atmospheric surface pressure may rise 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 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 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.

Artist's conception of a terraformed Mars. This portrayal is approximately centered on the prime meridian and 30 degrees north latitude, and a hypothesized ocean with a sea level at approximately two kilometers below average surface elevation. The ocean submerges what are now Vastitas Borealis, Acidalia Planitia, Chryse Planitia, and Xanthe Terra; the visible landmasses are Tempe Terra at the left, Aonia Terra at the bottom, Terra Meridiani at the lower right, and Arabia Terra at the upper right. Rivers that feed the ocean at the lower right occupy what are now Valles Marineris and Ares Vallis, while the large lake at the lower right occupies what is now Aram Chaos.

[edit] 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 chlorofluorocarbons (or CFCs) and perfluorocarbons (or PFCs) has been suggested. These gases are the most cited 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.

A proposal to mine fluorine-containing minerals as a source of CFCs and PFCs 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 is also a greenhouse gas.

[edit] 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. Another theory is that solar winds rip the atmosphere away from the planet as it becomes trapped in bubbles of magnetic fields called plasmoids.[6]

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.

[edit] See also

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