Colonization of Mars

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Many people^{[citation needed]} defend space colonization as a desirable and perhaps inevitable step in the future of humanity. Mars is the focus of much speculation and serious study about possible colonies. It is the second easiest planet to reach from Earth in terms of energy (delta V) requirements, but a trip there would require several months in space (with current technology, about 6-7 months).

Space colonization edit

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Contents 1 Similarity to Earth 2 Differences 3 Habitability 3.1 Terraforming of Mars 4 Radiation 5 Communication 6 Unmanned Precursors 7 Possible locations for colonies 7.1 Polar regions 7.2 Midlands 7.3 Valles Marineris 7.4 Martian Moons 8 Concerns 9 See also 10 Notes 11 References 12 External links

[edit] Similarity to Earth

While Earth is most like neighboring Venus in bulk composition, Mars' similarities to Earth are ultimately more compelling when considering colonization. These include:

• the Martian day (or sol) is very close to Earth's. A Mars solar day is 24 hours 39 minutes 35.244 seconds.^[1] See timekeeping on Mars.
• Mars has a surface area that is 28.4% of Earth's, only slightly less than the amount of dry land on Earth (which is 29.2% of Earth's surface).
• Mars has an axial tilt of 25.19°, compared with Earth's 23.44°. As a result, Mars has seasons much like Earth, though they last nearly twice as long because the Martian year is about 1.88 Earth years. The Martian north pole points at Cygnus, not Ursa Minor.
• Mars has an atmosphere. While very thin (about 0.7% of Earth's atmosphere), it provides some protection from solar and cosmic radiation and has been used successfully for aerobraking of spacecraft.
• Recent observations by NASA's Mars Exploration Rovers and ESA's Mars Express confirm the presence of water on Mars. Mars appears to have significant quantities of all the elements necessary to support Earth-based life.

[edit] Differences

There are differences, of course, between Earth and Mars:

• The surface gravity on Mars is only one third that of Earth. It is not known if this level is high enough to prevent the health problems associated with weightlessness.
• Mars is much colder than Earth, with a mean surface temperature of -63°C and a low of -140°C.
• There are no standing bodies of liquid water on the surface of Mars.
• Because Mars is farther from the Sun, the level of solar energy reaching the surface (the solar constant) is only about half of what reaches the Earth or the Moon.
• Mars' orbit is more eccentric than Earth's, exacerbating temperature and solar constant variations.
• The atmospheric pressure on Mars is much too low for humans to survive without pressure suits; habitable structures on Mars will need to be constructed with pressure vessels similar to spacecraft, capable of containing a pressure between a third and a whole bar.
• The Martian atmosphere consists mainly of carbon dioxide. However the partial pressure of CO₂ at the surface of Mars is some 52 times higher than on Earth, possibly allowing Mars to support plant life.
• Mars has no magnetosphere to deflect solar winds.

[edit] Habitability

Physiologically, Mars's atmosphere may be considered a vacuum. An unprotected human being would lose consciousness in about 20 seconds and would not survive more than a minute or so on the surface of Mars without a space suit.

Still, conditions on Mars are much closer to habitability than the extremely hot and cold temperatures on Mercury, the furnace-hot surface of Venus, or the cryogenic cold of the outer planets. Only the cloudtops of Venus are closer in terms of habitability to Earth than Mars is. There are natural settings on Earth where humans have explored that match most conditions on Mars. The highest altitude reached by a manned balloon ascent, a record set in May, 1961, was 34,668 meters (113,740 feet) The pressure at that altitude is about the same as on the surface of Mars.^{[citation needed]} Extreme cold in the Arctic and Antarctic match all but the most extreme temperatures on Mars.

[edit] Terraforming of Mars

Main article: Terraforming of Mars

Some groups have speculated, Mars might one day be transformed so as to allow a wide variety of living things, including humans, to survive unaided on Mars' surface.^[2] The practicality of terraforming is still unclear, and its ethics are also disputed.

[edit] Radiation

Mars has no global geomagnetic field comparable to Earth's. Combined with a thin atmosphere, this permits a significant amount of ionizing radiation to reach the Martian surface. The Mars Odyssey spacecraft carried an instrument, the Mars Radiation Environment Experiment (MARIE), to measure the dangers to humans. MARIE found that radiation levels in orbit above Mars are 2.5 times higher than at the International Space Station. Average doses were about 22 millirads per day (220 micrograys per day or 0.8 gray per year).^{[citation needed]} A three year exposure to such levels would be close to the safety limits currently adopted by NASA. Levels at the Martian surface would be somewhat lower and might vary significantly at different locations depending on altitude and local magnetic fields.

Occasional solar proton events (SPEs) produce much higher doses. Astronauts on Mars could be warned of SPEs by sensors closer to the Sun and presumably take shelter during these events.^[3] Some SPEs were observed by MARIE that were not seen by sensors near Earth due to the fact SPEs are directional. This would imply that a network of spacecraft in orbit around the Sun might be needed to ensure all SPEs threatening Mars were detected.^{[citation needed]}

Much remains to be learned about space radiation. In 2003, NASA's Lyndon B. Johnson Space Center opened a facility, the NASA Space Radiation Laboratory, at Brookhaven National Laboratory that employs particle accelerators to simulate space radiation. The facility will study its effects on living organisms along with shielding techniques.^[4]

There is some evidence that this kind of low level, chronic radiation is not quite as dangerous as once thought; and that radiation hormesis occurs.^[5] The general consensus among those that have studied the issues is that radiation levels, with the exception of the SPEs, that would be experienced on the surface of Mars, and whilst journeying there, are certainly a concern, but are not thought to prevent a trip from being made with current technology^[6].

[edit] Communication

Communications with Earth are relatively straightforward during the half-sol when the Earth is above the Martian horizon. NASA and ESA included communications relay equipment in several of the Mars orbiters, so Mars already has communications satellites. While these will eventually wear out, additional orbiters with communication relay capability are likely to be launched before any colonization expeditions are mounted.

The round trip communication delay due to the speed of light ranges from about 6.5 minutes at closest approach to 44 minutes at superior conjunction. Real-time conversation with Earth, such as telephone or instant messaging, is not possible, but other means of communication, such as e-mail and voice mail pose no difficulty. NASA has found that direct communication can be blocked for about two weeks every synodic period, around the time of superior conjunction when the Sun is directly between Mars and Earth.^[7] It should be remembered that the vast majority of exploration and colonization of Earth was conducted without the benefit of real-time communication with "home". Also a satellite at, say, either of the Earth-Sun L4/L5 Lagrange points could serve as a relay during this period.

Ordinary two-way radios or even cell phones will work well over line of sight distances and their range can be extended using radio repeaters on high ground or towers. Mars has an ionosphere that might be used to reflect radio communications between points farther apart on the Martian surface, somewhat like short wave communication on Earth. The peak plasma frequency in the Martian ionosphere is about 1 MHz (at about 150 km),^[8] suggesting that would be the maximum usable frequency for such communications. ^[9]

In any case, a constellation of communications satellites, perhaps including a Lagrangian point satellite located to avoid difficulties during superior conjunction, would be a minor expense in the context of a full-blown Mars colonization program.

[edit] Unmanned Precursors

The path to a manned Mars colony will be prepared by unmanned systems, such as the Mars Exploration Rovers Spirit and Opportunity. These systems will help locate resources, such as ground water or ice, that will help a colony to grow and thrive. The lifetimes of these systems will be measured in years and even decades, and as capital assets they will be owned and operated not only by governments but by commercial concerns, similar to Communications satellites. As such they will pioneer not only the development of the land of Mars, but also the laws regarding ownership and control. These unmanned systems also have a reduced cost versus early manned operations and have less political risk.

It will be possible to have unmanned systems lay the groundwork for early manned landings and bases. The production of various consumables will include fuel, oxiders, water, and construction materials. Establishing power, communications, shelter, heating, and manufacting basics can be begun with unmanned systems, if only as a prelude to manned operations.

[edit] Possible locations for colonies

Mars can be considered in broad regions for discussion of possible colony sites.

[edit] Polar regions

Mars' north and south poles once attracted great interest as colony sites because seasonally-varying polar ice caps have long been observed by telescope from Earth. Mars Odyssey found the largest concentration of water near the north pole, but also showed that water likely exists in lower latitudes as well, making the poles less compelling as a colony locale. Like Earth, Mars sees a midnight sun at the poles during local summer and polar night during local winter.

[edit] Midlands

The exploration of Mars' surface is still underway. The two Mars Exploration Rovers, Spirit and Opportunity, have encountered very different soil and rock characteristics. This suggests that the Martian landscape is quite varied and the ideal location for a colony would be better determined when more data becomes available. As on Earth, the further one goes from the equator, the greater the seasonal climate variation one encounters.

[edit] Valles Marineris

Valles Marineris, the "Grand Canyon" of Mars, is over 3,000 km long and averages 8 km deep. Atmospheric pressure at the bottom would be some 25% higher than the surface average, 0.9 kPa vs 0.7 kPa. The canyon runs roughly east-west, so shadows from its walls should not interfere too badly with solar power collection. River channels lead from the canyon, indicating it was once flooded.

[edit] Martian Moons

Whilst not strictly part of Mars itself, the moons are attractive for some kind of presence. The delta-v from the moons to an Earth return trajectory is low, and the moons may possess rocket propellant such as water ice in the rock. If so, they could act as refuelling points for vehicles returning to Earth, and would be economically viable to periodically return propellant and other material to cis lunar space. This could help pay for Martian surface settlement.

[edit] Concerns

Besides the general criticism of human colonization of space (see space colonization for a discussion), there are specific concerns about a colony on Mars:

• The question of whether life once existed or exists now on Mars has not been settled, raising concerns about possible contamination of the planet with Earth life. See Life on Mars.
• Radiation levels for trips to and from Mars are very high, quite significantly increasing the risk of cancer, and if child bearing age groups were sent this could possibly create birth defects.
• Critics of human exploration of Mars argue that the planet might be more economically explored by robots.
• Advocates of a return to the Moon say the Moon is a more logical first location for a first planetary colony, perhaps using it as a staging area for future manned missions to Mars, despite the Moon's extreme poverty in several of the key elements required for life, most notably hydrogen, nitrogen and carbon (50 - 100 ppm).^[10]
• It is unknown whether Martian gravity can support human life in the long term (all experience is at either 1g or zero gravity). Space medicine researchers have theorized on whether the health benefits of gravity rise slowly or quickly between weightlessness and full Earth gravity. The Mars Gravity Biosatellite experiment is due to become the first experiment testing the effects of partial gravity, artificially generated at 0.38 g to match Mars gravity, on mammal life, specifically on mice, throughout the life cycle from conception to death.^[11]
• Mars' escape velocity is 5 km/s, which, though less than half that for Earth, is reasonably high compared to the Moon's 2.38 km/s or the negligible escape velocity of most asteroids.^[12] This could make physical export trade from Mars to other planets and habitats less viable economically.

[edit] See also

• Exploration of Mars
• Mars
• Mars Direct
• MarsDrive
• Mars Analogue Research Station Programme
• Mars in fiction
• Mars Society
• NASA's Vision for Space Exploration
• Red Colony
• Solar system
• Space colonization in popular culture
• Terraforming
• The Case for Mars

[edit] Notes

[edit] References

• Frank Crossman and Robert Zubrin, editors, On to Mars: Colonizing a New World. Apogee Books Space Series, 2002, ISBN 1-896522-90-4.
• Robert Zubrin, The Case for Mars: The Plan to Settle the Red Planet and Why We Must, Simon & Schuster/Touchstone, 1996, ISBN 0-684-83550-9

[edit] External links

• The Planetary Society
• Red Colony web site
• MarsDrive Consortium
• 4Frontiers Corporation
• Mars Foundation
• Mars Society
• Google Mars
• TLU Mission to Mars