Terraforming of Mars: Wikis

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Artist's conception of the process of terraforming Mars.

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, thus providing the possibility of safe and sustainable colonization of 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 current 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.

Contents

Reasons for terraforming

In the future, population growth and demand for resources may create pressure for humans to colonize new habitats such as Mars, the moon and nearby planets, as well as mine the Solar System for energy and materials.[1] 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.

Background

Mars already consists of many soil minerals that could theoretically be used for terraforming. Additionally, recent research has revealed large amounts of ice permafrost just below the Martian surface down to latitude 60, as well as on the surface at the poles, where it is mixed with dry ice, frozen CO2. It has also been hypothesized that there are vast amounts of ice in the deeper crust. As frozen carbon dioxide (CO2) at the poles sublimes back into the atmosphere during the Martian summer, a small amount of water residue is left behind, which fast winds then sweep off the poles at speeds approaching 250 mph (400 km/h). This seasonal occurrence transports large amounts of dust and water vapor into the atmosphere, giving rise to Earth-like cirrus clouds.

Molecular oxygen is only present in the atmosphere in trace amounts, but the element of oxygen is present in the carbon dioxide that is the main component of the Martian atmosphere. Elemental oxygen is also present in large amounts in metal-oxides on the Martian surface. Some oxygen is also present in the soil in the form of per-nitrates.[2] An analysis of soil samples taken by the Phoenix lander indicated the presence of perchlorate, which has been used to liberate oxygen in chemical oxygen generators. Additionally, electrolysis could be employed to separate water on the planet into oxygen and hydrogen if sufficient liquid water and electricity were available.

It has been suggested that Mars once had an environment relatively similar to that of Earth during an earlier stage in its development. This similarity is indicated by the thickness of the Martian atmosphere, as well as the evident presence of liquid water on the planet's surface in the past. The atmosphere has thinned over millions of years as gases have escaped into space, although it has also partially condensed into solid form. While water once appears to have existed on the Martian surface, it now only appears to exist at the poles and just below the planetary surface as permafrost. The exact mechanisms which led to the current atmospheric conditions on Mars are not fully known, although several hypotheses have been proposed. One hypothesis is that the gravity of Mars today indicates that lighter gases in the upper atmosphere could have contributed to the thinning of the atmosphere, with the excess atoms escaping into space. The evident lack of plate tectonics on Mars is another plausible contributing factor, since a lack of tectonic activity would in theory slow the recycling of gases from being locked in sediments back into the atmosphere. The lack of a 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 a process are still not well known.

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.

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Building the atmosphere, water content

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.

Sources of water

A substantial, nearby source of water is the dwarf planet Ceres, which, according to various studies accounts for 25% to 33% of the mass of the Asteroid Belt[3][4][5]. Ceres' mass is approximately 9.43 x 10^20 kg. Estimates of how much of Ceres is water varies widely but 20% is a typical estimate and it is thought that much of the water forms the outer or near-surface level. The mass of Ceres' water equals approximately 1.886 x 10^20 kg using the previous estimates. The total mass of Mars is approximately 6.4185 x 10^23 kg.[6] Therefore a very rough estimate is that the amount of water on Ceres equals approximately 0.03 % of the total mass of Mars. As a side note, the total mass of Ceres is approximately 0.15 % that of Mars. Transporting a significant portion of this water, or water from any of the icy moons, would be daunting. Alternately, any attempt to perturb the orbit of Ceres in order to add it whole to Mars (similar to the strategy of using a gravitational tractor for asteroid deflection[7]), thus increasing Mars' mass by admittedly a tiny fraction but adding a great deal of heat (no small, cosmic body Ceres, see below), must account for any resultant perturbation of the martian orbit and account for prolonged geological tumult, such as reestablishment of hydrostatic equilibrium, that would result from even the softest of impacts.

Artist's conception of a terraformed Mars. This portrayal is approximately centered on the prime meridian and 30° 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.

Ammonia importation

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 is difficult.

Hydrocarbons importation

Another way would be to import methane or other hydrocarbons,[8][9] which are common in Titan's atmosphere (and on its surface). 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. These gases also 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

This reaction could probably 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.

Hydrogen importation

Hydrogen importation could also be done for atmospheric and hydrospheric engineering. For example, hydrogen could react with iron(III) oxide from the martian soil, that would give water as a product:

H2 + Fe2O3 => H2O + 2FeO

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. Alternatively, reacting hydrogen with the carbon dioxide atmosphere via the Sabatier reaction would yield methane and water.

Using perfluorocarbons

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.[10]

Adding heat

Adding heat and conserving the 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.[11] 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.

Changing the albedo of the Martian surface would also make more efficient use of incoming sunlight.[12] 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) or 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 extremophile 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.

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. Furthermore, the atmosphere would have a new small oxygen contribution from the algae, though it would still not be enough oxygen for humans to be able to breathe. 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.

Magnetic field and solar radiation

Earth abounds with water because its ionosphere is permeated with a magnetic field. The hydrogen ions present in its ionosphere move very fast due to their small mass, but they cannot escape to outer space because their trajectories are deflected by the magnetic field. Venus has dense atmosphere, but only traces of water vapor (20 ppm) because it has no magnetic field. The Martian atmosphere is devoid of water vapor for the same reason. It seems that the most practicable way to hold water and regulate temperature is building water-tight greenhouses on the surface of Mars. Another way to achieve these goals is building very large magnets and launching mirrors into orbit.

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. 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.[13]

Venus, however, shows that the lack of a magnetosphere does not preclude a dense (albeit dry) atmosphere. A thick atmosphere could also provide solar radiation protection to the surface. In the past, Earth has regularly had periods where the magnetosphere changed direction and collapsed for some time.

The lack of a protective magnetic field would also have possible health effects on colonists due to increased cosmic ray flux. The health threat depends on the flux, energy spectrum, and nuclear composition of the rays. The flux and energy spectrum depend on a variety of factors, which are incompletely understood. The Mars Radiation Environment Experiment (MARIE) was launched in 2001 in order to collect more data. Estimates are that humans unshielded in interplanetary space would receive annually roughly 400 to 900 milli-Sieverts (mSv) (compared to 2.4 mSv on Earth) and that a Mars mission (12 months in flight and 18 months on Mars) might expose shielded astronauts to ~500 to 1000 mSv.[14] These doses approach the 1 to 4 Sv career limits advised by the National Council on Radiation Protection and Measurements for Low Earth orbit activities.

In fiction

  • Total Recall, an American science fiction film from 1990; an example of popular culture speculation regarding the terraforming of Mars.
  • Red Faction trilogy, a science fiction trilogy of video games, takes place on a terraformed version 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.
  • Ilium/Olympos, a science fiction duology of novels by Dan Simmons which revolves around events staged on a far-future terraformed Mars.

See also

References

External links


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