Colonization of Mars
The colonization of Mars refers to the proposed establishment of permanent human settlements on the planet Mars.
It is the focus of serious study as Mars has been viewed as one of the primary candidates for permanent and extensive human colonization, because it is the most hospitable planet in the Solar System other than Earth, given its proximity and surface conditions which are similar to Earth relative to the other solar planets, such as the availability of frozen ground water. While the Moon due to its close proximity has been proposed as the first location for human colonization, lunar gravity is only 16% that of Earth's while Martian gravity is a more substantial 38%. There is more water present on Mars than the Moon, and Mars has a thin atmosphere. These factors give Mars a greater potential capacity to host organic life and human colonization.
Permanent human habitation on a planetary body other than the Earth is one of science fiction's most prevalent themes. As technology has advanced, and concerns about the future of humanity on Earth have increased, the argument that space colonization is an achievable and worthwhile goal has gained momentum.
Relative similarity to Earth
- The Martian day (or sol) is very close in duration to Earth's. A solar day on Mars is 24 hours 39 minutes 35.244 seconds. (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 half the radius of Earth and only one-tenth the mass. This means that it has a smaller volume (~15%) and lower average density than Earth.
- 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 currently points at Cygnus, not Ursa Minor.
- Mars has an atmosphere. Although it is 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, ESA's Mars Express and NASA's Phoenix Lander confirm the presence of water ice on Mars.
Differences from Earth
- While there are kinds of micro-organisms that survive in a great variety of environmental conditions, including some Martian conditions, plants and animals generally cannot survive the ambient conditions on the surface of Mars.
- The surface gravity on Mars is 38% of that on Earth. It is not known if this is enough to prevent the health problems associated with weightlessness.
- Mars is much colder than Earth, with a mean surface temperature between 186–268 K (−87 °C to −5 °C). The lowest temperature ever recorded on Earth was −89.2 °C, in Antarctica.
- There are no standing bodies of liquid water on the surface of Mars.
- Because Mars is further from the Sun, the amount of solar energy reaching the upper atmosphere (the solar constant) is less than half of what reaches the Earth's upper atmosphere or the Moon's surface. However, the solar energy that reaches the surface of Mars is not impeded by a thick atmosphere and magnetosphere like on Earth.
- Mars' orbit is more eccentric than Earth's, exacerbating temperature and solar constant variations.
- The atmospheric pressure on Mars is ~6 mbar, far below the Armstrong Limit (61.8 mbar) at which people cannot survive without pressure suits. Since terraforming cannot be expected as a near-term solution, habitable structures on Mars would 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. Because of this, even with the reduced atmospheric pressure, the partial pressure of CO2 at the surface of Mars is some 15 times higher than on Earth. It also has significant levels of carbon monoxide.
- Mars has a very weak magnetosphere, so it deflects solar winds poorly.
Conditions for human habitation
Based on scientific evidence, collected by satellites and the NASA Rovers, conditions are not “hospitable” to humans or life as we know it. Antarctica has temperatures that are comparable, though Mars is colder, but other environmental circumstances are very unlike those of Earth, in fact would be deadly to most life as we know it. These include greatly reduced air pressure, an atmosphere that’s 95% carbon dioxide, almost no oxygen (compared to Earth’s 21% oxygen and almost no carbon dioxide), reduced gravity, and no liquid water (although amounts of frozen water have been detected). Despite this, some consider Mars to be “habitable,” but only if life support measures were taken. People would need to live in artificial environments. Man might one day step foot on Mars and scout around, but it’s unknown if man could ever adapt to living on Mars as a permanent resident.
It may be possible to terraform Mars to allow a wide variety of living things, including humans, to survive unaided on Mars' surface.
In April 2012, it was reported that some lichen and cyanobacteria survived and showed remarkable adaptation capacity for photosynthesis after 34 days in simulated Martian conditions in the Mars Simulation Laboratory (MSL) maintained by the German Aerospace Center (DLR).
Mars has no global magnetic field comparable to Earth's geomagnetic field. 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 0.08 gray per year.) 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. Building living quarters underground (possibly in lava tubes that are already present) would significantly lower the colonists' exposure to radiation.
Occasional solar proton events (SPEs) produce much higher doses. Some SPEs were observed by MARIE that were not seen by sensors near Earth due to the fact that SPEs are directional, making it difficult to warn astronauts on Mars early enough.
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 studies its effects on living organisms along with shielding techniques. Initially, there was some evidence that this kind of low level, chronic radiation is not quite as dangerous as once thought; and that radiation hormesis occurs. In 2006 it was determined that protons from cosmic radiation actually cause twice as much serious damage to DNA as previously expected, exposing astronauts to grave risks of cancer and other diseases. Because of radiation, the summary report of the Review of U.S. Human Space Flight Plans Committee released on 2009 reported that "Mars is not an easy place to visit with existing technology and without a substantial investment of resources." NASA is exploring alternative technologies such as "deflector" shields of plasma to protect astronauts and spacecraft from radiation.
Mars requires less energy per unit mass (delta V) to reach from Earth than any planet except Venus. Using a Hohmann transfer orbit, a trip to Mars requires approximately nine months in space. Modified transfer trajectories that cut the travel time down to seven or six months in space are possible with incrementally higher amounts of energy and fuel compared to a Hohmann transfer orbit, and are in standard use for robotic Mars missions. Shortening the travel time below about six months requires higher delta-v and an exponentially increasing amount of fuel, and is not feasible with chemical rockets, but would be perfectly feasible with advanced spacecraft propulsion technologies, some of which have already been tested, such as VASIMR, and nuclear rockets. In the former case, a trip time of forty days could be attainable, and in the latter, a trip time down to about two weeks. Another possibility is constant-acceleration technologies such as space-proven solar sails and ion drives which permit passage times at close approaches on the order of several weeks.
During the journey the astronauts are subject to radiation, which requires a means to protect them. Cosmic radiation and solar wind cause DNA damage, which increases the risk of cancer significantly. The effect of long term travel in interplanetary space is unknown, but scientists estimate an added risk of between 1% and 19%, most likely 3.4%, for men to die of cancer because of the radiation during the journey to Mars and back to Earth. For women the probability is higher due to their larger glandular tissues.
Landing on Mars
Mars has a gravity 0.38 times that of the Earth and the density of its atmosphere is 1% of that on Earth. The relatively strong gravity and the presence of aerodynamic effects makes it difficult to land heavy, crewed spacecraft with thrusters only, as was done with the Apollo moon landings, yet the atmosphere is too thin for aerodynamic effects to be of much help in braking and landing a large vehicle. Landing piloted missions on Mars will require braking and landing systems different from anything used to land crewed spacecraft on the Moon or robotic missions on Mars.
If one assumes carbon nanotube construction material will be available with a strength of 130 GPa then a space elevator could be built to land people and material on Mars. A space elevator on Phobos has also been proposed.
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 one-way communication delay due to the speed of light ranges from about 3 minutes at closest approach (approximated by perihelion of Mars minus aphelion of Earth) to 22 minutes at the largest possible superior conjunction (approximated by aphelion of Mars plus aphelion of Earth). Real-time communication, such as telephone conversations or Internet Relay Chat, between Earth and Mars would be highly impractical due to the long time lags involved. 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, although the actual duration of the communications blackout varies from mission to mission depending on various factors - such as the amount of link margin designed into the communications system, and the minimum data rate that is acceptable from a mission standpoint. In reality most missions at Mars have had communications blackout periods of the order of a month.
A satellite at either of the Earth-Sun L4/L5 Lagrange points could serve as a relay during this period to solve the problem; even a constellation of communications satellites would be a minor expense in the context of a full colonization program. However, the size and power of the equipment needed for these distances make the L4 and L5 locations unrealistic for relay stations, and the inherent stability of these regions, while beneficial in terms of station-keeping, also attracts dust and asteroids, which could pose a risk. Despite that concern, the STEREO probes passed through the L4 and L5 regions without damage in late 2009.
Recent work by the University of Strathclyde's Advanced Space Concepts Laboratory, in collaboration with the European Space Agency, has suggested an alternative relay architecture based on highly non-Keplerian orbits. These are a special kind of orbit produced when continuous low-thrust propulsion, such as that produced from an ion engine or solar sail, modifies the natural trajectory of a spacecraft. Such an orbit would enable continuous communications during solar conjunction by allowing a relay spacecraft to "hover" above Mars, out of the orbital plane of the two planets. Such a relay avoids the problems of satellites stationed at either L4 or L5 by being significantly closer to the surface of Mars while still maintaining continuous communication between the two planets.
The path to a human colony could be prepared by robotic systems such as the Mars Exploration Rovers Spirit, Opportunity and Curiosity. These systems could help locate resources, such as ground water or ice, that would help a colony grow and thrive. The lifetimes of these systems would be measured in years and even decades, and as recent developments in commercial spaceflight have shown, it may be that these systems will involve private as well as government ownership. These robotic systems also have a reduced cost compared with early crewed operations, and have less political risk.
Wired systems might lay the groundwork for early crewed landings and bases, by producing various consumables including fuel, oxidizers, water, and construction materials. Establishing power, communications, shelter, heating, and manufacturing basics can begin with robotic systems, if only as a prelude to crewed operations.
Mars Surveyor 2001 Lander MIP (Mars ISPP Precursor) was to demonstrate manufacture of oxygen from the atmosphere of Mars, and test solar cell technologies and methods of mitigating the effect of Martian dust on the power systems.
Early human missions
In 1952, Wernher von Braun described in his book Das Marsprojekt that a fleet of 10 spaceships could be built using 1000 three-stage rockets. These could bring a population of 70 people to Mars.
Early real-life human missions to Mars however, such as those being tentatively planned by NASA, FKA and ESA would not be direct precursors to colonization. They are intended solely as exploration missions, as the Apollo missions to the Moon were not planned to be sites of a permanent base.
Colonization requires the establishment of permanent bases that have potential for self-expansion. A famous proposal for building such bases is the Mars Direct and the Mars Semi-Direct plan, advocated by Robert Zubrin.
The Mars Society has established the Mars Analogue Research Station Programme at sites Devon Island in Canada and in Utah, United States, to experiment with different plans for human operations on Mars, based on Mars Direct. Modern Martian architecture concepts often include facilities to produce oxygen and propellant on the surface of the planet.
As with early colonies in the New World, economics would be a crucial aspect to a colony's success. The reduced gravity well of Mars and its position in the solar system may facilitate Mars-Earth trade and provide the rationalization for continued settlement of the planet. Given its size and resources, this might eventually be a place to grow food and produce equipment that would be used by miners in the asteroid belt.
Mars' reduced gravity together with its rotation rate makes it possible for the construction of a space elevator with today's materials, although the low orbit of Phobos could present engineering challenges. If constructed, the elevator could transport minerals and other natural resources extracted from the planet.
A major economic problem is the enormous up-front investment required to establish the colony and perhaps also terraform the planet.
Some early Mars colonies might specialize in developing local resources for Martian consumption, such as water and/or ice. Local resources can also be used in infrastructure construction. One source of Martian ore currently known to be available is reduced iron in the form of nickel-iron meteorites. Iron in this form is more easily extracted than from the iron oxides that cover the planet.
Another main inter-Martian trade good during early colonization could be manure. Assuming that life doesn't exist on Mars, the soil is going to be very poor for growing plants, so manure and other fertilizers will be valued highly in any Martian civilization until the planet changes enough chemically to support growing vegetation on its own.
Solar power is a candidate for power for a Martian colony. Solar insolation (the amount of solar radiation that reaches Mars) is about 42% of that on Earth, since Mars is about 52% farther from the Sun and insolation falls off as the square of distance. But the thin atmosphere would allow almost all of that energy to reach the surface as compared to Earth, where the atmosphere absorbs roughly a quarter of the solar radiation. Sunlight on the surface of Mars would be much like a moderately cloudy day on Earth.
Nuclear power is also a good candidate, since the fuel is very dense for cheap transportation from Earth. Nuclear power also produces heat, which would be extremely valuable to a Mars colony.
Possible locations for settlements
Broad regions of Mars can be considered for possible settlement sites.
Mars' north and south poles once attracted great interest as settlement 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 settlement locale. Like Earth, Mars sees a midnight sun at the poles during local summer and polar night during local winter.
Mars Odyssey found what appear to be natural caves near the volcano Arsia Mons. It has been speculated that settlers could benefit from the shelter that these or similar structures could provide from radiation and micrometeoroids. Geothermal energy is also suspected in the equatorial regions.
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 settlement would be better determined when more data becomes available. As on Earth, seasonal variations in climate become greater with distance from the equator.
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. River channels lead to the canyon, indicating it was once flooded.
Several lava tube skylights on Mars have been located. Earth based examples indicate that some should have lengthy passages offering complete protection from radiation and be relatively easy to seal using on site materials, especially in small subsections.
Making Mars colonization a reality is advocated by several groups with different reasons and proposals. One of the oldest is the Mars Society. They promote a NASA program to accomplish human exploration of Mars and have set up Mars analog research stations in Canada and the United States. Also are MarsDrive, which is dedicated to private initiatives for the exploration and settlement of Mars, and, Mars to Stay, which advocates recycling emergency return vehicles into permanent settlements as soon as initial explorers determine permanent habitation is possible. An initiative that went public in June 2012 is Mars One. Its aim is to establish a fully operational permanent human colony on Mars by 2023.
Besides the general criticism of human colonization of space (see space colonization), there are specific concerns about a colony on Mars:
- Mars has a gravity 0.38 times that of the Earth and a density of the atmosphere of 1% that on Earth. The stronger gravity than the Moon and the presence of aerodynamic effects makes it more difficult to land heavy, crewed spacecraft with thrusters only, yet the atmosphere is also too thin to get very much use out of aerodynamic effects for braking and landing. Landing piloted missions on Mars will require a braking and landing system different from anything used to land crewed spacecraft on the Moon or robotic missions on Mars.
- Mars is currently a category IV destination under COSPAR, which means that any mission to the surface must be rated to keep it free from contamination by living organisms, in case of a hard landing. It seems unlikely that COSPAR and the Outer Space Treaty can be changed to permit a landing on Mars surface until a lot more is known about the planet than we do now. If ever it does, the legal process will surely be a long one. See also: Legal Protection of Earth and Mars from forward and backward contamination
- 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. Even if Mars is lifeless, it is generally agreed that a manned mission to Mars would inevitably introduce many Earth micro-organisms to the planet. Recent research has shown that at least some of these organisms can remain viable on the surface of Mars, and that there may be habitats on Mars where they could reproduce. If this happens, it will make it impossible to study a biologically pristine Mars. These concerns are addressed in the planetary protection policy of the Committee on Space Research which is largely followed by NASA. It is impossible for a manned landing on Mars to comply with the current policy. See also Contamination concerns for surface missions to Mars
- The atmosphere of Mars is essentially equivalent to a vacuum on Earth (see Atmosphere of Mars). It still requires use of space-suits, especially designed for Mars.
- The Martian atmosphere is very cold by a standard of human habitability, with an average temperature of −55 °C (−67 °F) and large day-to-night temperature swings of typically 60-80°C (see Climate of Mars)
- 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. One theory is that sleeping chambers built inside centrifuges would minimize the health problems. The Mars Gravity Biosatellite experiment was 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. However, in 2009 the Biosatellite project was cancelled due to lack of funds.
- Mars' escape velocity is 5 km/s, which, though less than half that for Earth (11.2 km/s), is reasonably high compared to the Moon's 2.38 km/s or the negligible escape velocity of most asteroids and orbital colonies. This could make physical export trade from Mars to other planets and habitats less viable economically.
- There is likely to be little economic return from the colonization of Mars while Lunar and Near Earth Asteroid industry is likely to be exporting to Earth.
- The answer time between Mars and Earth is from about 8 minutes to more than 24 minutes.
- Solar power on Mars is limited.
- It is much lower than on Earth (about 44% of the intensity on Earth) due to its greater distance from the sun.
- Mars has dust storms which can reduce solar power. The largest of these storms can cover much of the planet and quite commonly last for months.
- Although a solar furnace on Mars could have a focus as large and as hot as a solar furnace on Earth, for the same size and temperature focus the mirror or lens would need to have about 1.5 times as great an aperture and be 1.5 times as far from the focal point.
- Mars has some disadvantages for growing plants compared with some other locations for space colonies. Since the storms can last for over a month and block out most of the light, artificial light would need to be supplied to keep the plants alive during the storms. Habitats also have to be heated because of night time lows that can reach below -80 °C. The habitats still have to be pressurised like any other space habitat because the atmosphere is a near vacuum (less than 1% of Earth's). They have to be oxygenated because plants need oxygen for their roots. Only lichens and extremophiles can possibly grow on the surface of Mars unassisted.
One possible approach that solves many of these issues is to develop an orbital colony around Mars initially, instead of a surface colony. This would permit humans to explore the surface of Mars in real time using telepresence, for less cost and more science return. For instance, astronauts would have remote access wherever there are remotely controlled devices on Mars. They could supervise several missions. Automatic functions would continue when direct control is not needed. An orbital colony could make use of local resources. Deimos, for instance, might hold carbon and water ice. Determining what material is available from Deimos and Phobos is a high priority for humanity's progress in outer space. See Exploration of the surface from orbit, via telerobotics and telepresence
A few instances in fiction provide detailed descriptions of Mars colonization. They include:
- Aria by Kozue Amano
- Axis by Robert Charles Wilson
- Icehenge (1985), the Mars trilogy (Red Mars, Green Mars, Blue Mars, 1992–1996), and The Martians (1999) by Kim Stanley Robinson
- First Landing (2002) by Robert Zubrin
- Man Plus (1976) by Frederik Pohl
- "We Can Remember It for You Wholesale" (1966), by Philip K. Dick
- Mars (1992) and Return to Mars (1999), by Ben Bova
- Climbing Olympus (1994), by Kevin J. Anderson
- Red Faction (2001), developed by Volition, published by THQ
- The Platform (2011) by James Garvey
- "The Destruction of Faena" (1974) by Alexander Kazantsev
- The Martian Chronicles (1950) by Ray Bradbury
- Exploration of Mars
- Human outpost (artificially created controlled human habitat)
- In-Situ Resource Utilization
- List of manned Mars mission plans in the 20th century
- Manned mission to Mars
- Mars Direct
- Mars Desert Research Station
- Mars One
- Mars Society
- Mars to Stay
- Inspiration Mars
- NASA's Vision for Space Exploration
- Terraforming of Mars
- Solar System
- Space architecture
- Space weather
- The Case for Mars
- Water on Mars
- Atmosphere of Mars
- Climate of Mars
- Criticism of the Space Shuttle program#Retrospect
- Michael D. Griffin#Long-term vision for space
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- Mars Society
- The Planetary Society: Mars Millennium Project
- 4Frontiers Corporation
- The Mars Foundation