Colonization of Mars
Overview
The colonization of Mars by humans is the focus of speculation and serious study because the surface conditions and availability of water on Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

 make it arguably the most hospitable planet in the solar system other than Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

. The Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 has been proposed as the first location for human colonization, but Mars has a thin atmosphere, giving it the potential capacity to host human and other organic life.
Encyclopedia
The colonization of Mars by humans is the focus of speculation and serious study because the surface conditions and availability of water on Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

 make it arguably the most hospitable planet in the solar system other than Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

. The Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 has been proposed as the first location for human colonization, but Mars has a thin atmosphere, giving it the potential capacity to host human and other organic life. Both the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 and Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

, as potential colonization sites, have the disadvantages of cost and risk associated with landing down deep gravity wells
Gravity well
A gravity well or gravitational well is a conceptual model of the gravitational field surrounding a body in space. The more massive the body the deeper and more extensive the gravity well associated with it. The Sun has a far-reaching and deep gravity well. Asteroids and small moons have much...

, which may make asteroids
Asteroid mining
Asteroid mining refers to the possibility of exploiting raw materials from asteroids and planetoids in space, including near-Earth objects. Minerals and volatiles could be mined from an asteroid or spent comet to provide space construction material , to extract water and oxygen to sustain the lives...

 another option for early expansion of humans into the solar system
Space colonization
Space colonization is the concept of permanent human habitation outside of Earth. Although hypothetical at the present time, there are many proposals and speculations about the first space colony...

.

Relative similarity to Earth

The Earth is much like its "sister planet" Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

 in bulk composition, size and surface gravity but Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

' similarities to Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 are 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. (See timekeeping on Mars
    Timekeeping on Mars
    Various schemes have been used or proposed to keep track of time and date on the planet Mars independently of Earth time and calendars.Mars has an axial tilt and a rotation period similar to those of Earth. Thus it experiences seasons of spring, summer, autumn and winter much like Earth, and its...

    .)
  • 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
    Axial tilt
    In astronomy, axial tilt is the angle between an object's rotational axis, and a line perpendicular to its orbital plane...

     of 25.19°, compared with Earth's 23.44°. As a result, Mars has season
    Season
    A season is a division of the year, marked by changes in weather, ecology, and hours of daylight.Seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earth's axis relative to the plane of revolution...

    s 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
    Cygnus (constellation)
    Cygnus is a northern constellation lying on the plane of the Milky Way. Its name is the Latinized Hellenic word for swan. One of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross...

    , not Ursa Minor
    Ursa Minor
    Ursa Minor , also known as the Little Bear, is a constellation in the northern sky. Like the Great Bear, the tail of the Little Bear may also be seen as the handle of a ladle, whence the name Little Dipper...

    .
  • Mars has an atmosphere. Although it is very thin (about 0.7% of Earth's atmosphere
    Earth's atmosphere
    The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

    ) it provides some protection from solar and cosmic radiation and has been used successfully for aerobraking
    Aerobraking
    Aerobraking is a spaceflight maneuver that reduces the high point of an elliptical orbit by flying the vehicle through the atmosphere at the low point of the orbit . The resulting drag slows the spacecraft...

     of spacecraft.
  • Recent observations by NASA
    NASA
    The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

    's Mars Exploration Rover
    Mars Exploration Rover
    NASA's Mars Exploration Rover Mission is an ongoing robotic space mission involving two rovers, Spirit and Opportunity, exploring the planet Mars...

    s, ESA's Mars Express
    Mars Express
    Mars Express is a space exploration mission being conducted by the European Space Agency . The Mars Express mission is exploring the planet Mars, and is the first planetary mission attempted by the agency. "Express" originally referred to the speed and efficiency with which the spacecraft was...

     and NASA's Phoenix Lander confirm the presence of water
    Water
    Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

     ice on Mars. Mars appears to have significant quantities of all the elements
    Chemical element
    A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...

     necessary to support Earth-based life.

Differences from Earth

  • The surface gravity
    Surface gravity
    The surface gravity, g, of an astronomical or other object is the gravitational acceleration experienced at its surface. The surface gravity may be thought of as the acceleration due to gravity experienced by a hypothetical test particle which is very close to the object's surface and which, in...

     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 of −63 °C and a low of −140 °C. The lowest temperature ever recorded on Earth
    Extremes on Earth
    This article describes extreme locations on Earth. Entries listed in bold are Earth-wide extremes.-Extreme elevations and temperatures per continent:This article describes extreme locations on Earth. Entries listed in bold are Earth-wide extremes....

     was −89.2 °C, in Antarctica.
  • There are no standing bodies of liquid water on the surface of Mars.
  • Because Mars is farther from the Sun
    Sun
    The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

    , the amount of solar energy reaching the upper atmosphere (the solar constant
    Solar constant
    The solar constant, a measure of flux density, is the amount of incoming solar electromagnetic radiation per unit area that would be incident on a plane perpendicular to the rays, at a distance of one astronomical unit...

    ) is less than half of what reaches the Earth's upper atmosphere or the Moon
    Moon
    The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

    's surface. However, the solar energy that reaches the surface of Mars is not impeded by a thick atmosphere 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
    Armstrong Limit
    The Armstrong limit, often called Armstrong's line, is the altitude that produces an atmospheric pressure so low that water boils at the normal temperature of the human body: 37 °C . It is named after Harry George Armstrong, who founded the U.S. Air Force’s Department of Space Medicine in...

     (61.8 mbar) at which people can survive without pressure suits. Since terraforming
    Terraforming of 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...

     cannot be expected as a near-term solution, habitable structures on Mars would need to be constructed with pressure vessel
    Pressure vessel
    A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...

    s similar to spacecraft, capable of containing a pressure between a third and a whole bar.
  • The Martian atmosphere consists mainly of carbon dioxide
    Carbon dioxide
    Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

    . Because of this, even with the reduced atmospheric pressure, the partial pressure
    Partial pressure
    In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture....

     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
    Magnetosphere
    A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...

    , so it deflects solar wind
    Solar wind
    The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...

    s poorly.

Habitability

Conditions on the surface of Mars are much closer to habitability than the surface of any other known planet or moon, as seen by the extremely hot and cold temperatures on Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...

, the furnace-hot surface of Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

, or the cryogenic cold of the outer planets and their moons. Only the cloud tops 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
High altitude balloon
High-altitude balloons are unmanned balloons, usually filled with helium or hydrogen that are released into the stratosphere, generally reaching between ....

 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. Extreme cold in the Arctic and Antarctic
Antarctic
The Antarctic is the region around the Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica and the ice shelves, waters and island territories in the Southern Ocean situated south of the Antarctic Convergence...

 match all but the most extreme temperatures on Mars.

Terraforming

It may be possible to terraform Mars to allow a wide variety of living things, including humans, to survive unaided on Mars' surface.

Radiation

Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

 has no global magnetic field comparable to Earth's geomagnetic field. Combined with a thin atmosphere, this permits a significant amount of ionizing radiation
Ionizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...

 to reach the Martian surface. The Mars Odyssey
2001 Mars Odyssey
2001 Mars Odyssey is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectrometers and electronic imagers to hunt for evidence of past or...

 spacecraft carried an instrument, the Mars Radiation Environment Experiment
Mars Radiation Environment Experiment
The Martian Radiation Experiment, or MARIE was designed to measure the radiation environment of Mars using an energetic particle spectrometer as part of the science mission of the 2001 Mars Odyssey spacecraft...

 (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
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...

. Average doses were about 22 millirads
Rad (unit)
The rad is a unit of absorbed radiation dose. The rad was first proposed in 1918 as "that quantity of X rays which when absorbed will cause the destruction of the malignant mammalian cells in question..." It was defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by...

 per day (220 micrograys
Gray (unit)
The gray is the SI unit of absorbed radiation dose of ionizing radiation , and is defined as the absorption of one joule of ionizing radiation by one kilogram of matter ....

 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.

Occasional solar proton event
Solar proton event
A Solar proton event occurs when protons emitted by the Sun become accelerated to very high energies either close to the Sun during a solar flare or in interplanetary space by the shocks associated with coronal mass ejections. These high energy protons cause several effects. They can penetrate the...

s (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
Lyndon B. Johnson Space Center
The Lyndon B. Johnson Space Center is the National Aeronautics and Space Administration's center for human spaceflight training, research and flight control. The center consists of a complex of 100 buildings constructed on 1,620 acres in Houston, Texas, USA...

 opened a facility, the NASA Space Radiation Laboratory, at Brookhaven National Laboratory
Brookhaven National Laboratory
Brookhaven National Laboratory , is a United States national laboratory located in Upton, New York on Long Island, and was formally established in 1947 at the site of Camp Upton, a former U.S. Army base...

 that employs particle accelerator
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...

s to simulate space radiation. The facility will study its effects on living organisms along with shielding techniques. There is some evidence that this kind of low level, chronic radiation is not quite as dangerous as once thought; and that radiation hormesis
Radiation hormesis
Radiation hormesis is the hypothesis that low doses of ionizing radiation are beneficial, stimulating the activation of repair mechanisms that protect against disease, that are not activated in absence of ionizing radiation...

 occurs. The 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 while journeying there, are certainly a concern, but are not thought to prevent a trip from being made with current technology.

Interplanetary spaceflight

Mars requires less energy per unit mass (delta V) to reach from Earth than any planet except Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

. Using a Hohmann transfer orbit
Hohmann transfer orbit
In orbital mechanics, the Hohmann transfer orbit is an elliptical orbit used to transfer between two circular orbits, typically both in the same plane....

, 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
Delta-v
In astrodynamics a Δv or delta-v is a scalar which takes units of speed. It is a measure of the amount of "effort" that is needed to change from one trajectory to another by making an orbital maneuver....

 and an exponentially increasing amount of fuel, and is not feasible with chemical rockets, but would be perfectly feasible with advanced spacecraft propulsion
Spacecraft propulsion
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the...

 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 sail
Solar sail
Solar sails are a form of spacecraft propulsion using the radiation pressure of light from a star or laser to push enormous ultra-thin mirrors to high speeds....

s and ion drives which permit passage times at close approaches on the order of several weeks. Both of these propulsion systems have been deployed and could readily obtain a constant acceleration of 0.1 g
G-force
The g-force associated with an object is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces acting on an object free to move. The accelerations that are not produced by gravity are termed proper accelerations, and...

.

During the journey the astronauts are subject to radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

, which requires a means to protect them. Cosmic radiation and solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...

 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 male persons 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
Space elevator
A space elevator, also known as a geostationary orbital tether or a beanstalk, is a proposed non-rocket spacelaunch structure...

 could be built to land men and material on Mars.
A space elevator on Phobos has also been proposed.

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 satellite
Communications satellite
A communications satellite is an artificial satellite stationed in space for the purpose of telecommunications...

s. 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
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...

 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
Internet Relay Chat
Internet Relay Chat is a protocol for real-time Internet text messaging or synchronous conferencing. It is mainly designed for group communication in discussion forums, called channels, but also allows one-to-one communication via private message as well as chat and data transfer, including file...

, 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
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 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 / 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 asteroids, which could pose a severe risk to any satellite.

Recent work by the University of Strathclyde
University of Strathclyde
The University of Strathclyde , Glasgow, Scotland, is Glasgow's second university by age, founded in 1796, and receiving its Royal Charter in 1964 as the UK's first technological university...

's Advanced Space Concepts Laboratory, in collaboration with the European Space Agency
European Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...

, 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.

Robotic precursors

The path to a human colony could be prepared by robotic
Robotic spacecraft
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...

 systems such as the Mars Exploration Rover
Mars Exploration Rover
NASA's Mars Exploration Rover Mission is an ongoing robotic space mission involving two rovers, Spirit and Opportunity, exploring the planet Mars...

s Spirit and Opportunity. 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.

Early human missions

Early human missions to Mars, such as those being tentatively planned by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

, 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
Mars Direct
Mars Direct is a proposal for a manned mission to Mars. Proponents of the scheme have claimed it to be both cost-effective and that it can be conducted with current technology. It was originally detailed in a research paper by NASA engineers Robert Zubrin and David Baker in 1990, and later expanded...

 plan, advocated by Robert Zubrin
Robert Zubrin
Robert Zubrin is an American aerospace engineer and author, best known for his advocacy of the manned exploration of Mars. He was the driving force behind Mars Direct—a proposal intended to produce significant reductions in the cost and complexity of such a mission...

. The Mars Society
Mars Society
The Mars Society is an international space advocacy non-profit organization dedicated to promoting the human exploration and settlement of the planet Mars. It was founded by Robert Zubrin and others in 1998 and attracted the support of notable science fiction writers and filmmakers, including Kim...

 has established the Mars Analogue Research Station Programme at sites Devon Island
Devon Island
Devon Island , claimed to be the largest uninhabited island on Earth, is located in Baffin Bay, Qikiqtaaluk Region, Nunavut, Canada. It is one of the larger members of the Canadian Arctic Archipelago, the second-largest of the Queen Elizabeth Islands, Canada's sixth largest island, and the 27th...

 in Canada and in Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

, 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.

Economics

As with early colonies in the New World
New World
The New World is one of the names used for the Western Hemisphere, specifically America and sometimes Oceania . The term originated in the late 15th century, when America had been recently discovered by European explorers, expanding the geographical horizon of the people of the European middle...

, 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.

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
Phobos (moon)
Phobos is the larger and closer of the two natural satellites of Mars. Both moons were discovered in 1877. With a mean radius of , Phobos is 7.24 times as massive as Deimos...

 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
Ore resources on Mars
Mars may contain valuable ores that will be very useful to future colonists. The abundance of volcanic features together with widespread cratering are strong evidence for a variety of ores.- How deposits are made :...

 currently known to be available is reduced iron in the form of nickel-iron meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...

s. 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
Manure
Manure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil...

 and other fertilizers will be valued highly in any Martian
Martian
As an adjective, the term martian is used to describe anything pertaining to the planet Mars.However, a Martian is more usually a hypothetical or fictional native inhabitant of the planet Mars. Historically, life on Mars has often been hypothesized, although there is currently no solid evidence of...

 civilization until the planet changes enough chemically to support growing vegetation on its own.

Solar power
Solar power
Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available...

 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.

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.

Heating requirements could be lowered if the colonists use domes to trap solar heat, especially for greenhouse
Greenhouse
A greenhouse is a building in which plants are grown. These structures range in size from small sheds to very large buildings...

s.

Possible locations for colonies

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

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 latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

s as well, making the poles less compelling as a colony locale. Like Earth, Mars sees a midnight sun
Midnight sun
The midnight sun is a natural phenomenon occurring in summer months at latitudes north and nearby to the south of the Arctic Circle, and south and nearby to the north of the Antarctic Circle where the sun remains visible at the local midnight. Given fair weather, the sun is visible for a continuous...

 at the poles during local summer and polar night
Polar night
The polar night occurs when the night lasts for more than 24 hours. This occurs only inside the polar circles. The opposite phenomenon, the polar day, or midnight sun, occurs when the sun stays above the horizon for more than 24 hours.-Description:...

 during local winter.

Equatorial regions

Mars Odyssey found what appear to be natural caves near the volcano Arsia Mons. It has been speculated that colonists could benefit from the shelter that these or similar structures could provide from radiation and micrometeroids. Geothermal energy is also suspected in the equatorial regions.

Midlands

The exploration of Mars' surface is still underway. The two Mars Exploration Rover
Mars Exploration Rover
NASA's Mars Exploration Rover Mission is an ongoing robotic space mission involving two rovers, Spirit and Opportunity, exploring the planet Mars...

s, 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, seasonal variations in climate become greater with distance from the equator.

Valles Marineris

Valles Marineris
Valles Marineris
Valles Marineris is a system of canyons that runs along the Martian surface east of the Tharsis region...

, the "Grand Canyon
Grand Canyon
The Grand Canyon is a steep-sided canyon carved by the Colorado River in the United States in the state of Arizona. It is largely contained within the Grand Canyon National Park, the 15th national park in the United States...

" 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
KPA
KPA may refer to:* Kenya Ports Authority* Kiln phosphoric acid, a dry process to produce phosphoric acid at high temperature in a kiln* Kilopascal , a unit of pressure* Known-plaintext attack, a method of cryptanalysis* Korean People's Army...

 vs 0.7 kPa. River channels lead to the canyon, indicating it was once flooded.

Lava tubes

Several lava tube
Lava tube
Lava tubes are natural conduits through which lava travels beneath the surface of a lava flow, expelled by a volcano during an eruption. They can be actively draining lava from a source, or can be extinct, meaning the lava flow has ceased and the rock has cooled and left a long, cave-like...

 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.

Advocacy

Making Mars colonization a reality is advocated by several groups with different reasons and proposals. One of the oldest is the Mars Society
Mars Society
The Mars Society is an international space advocacy non-profit organization dedicated to promoting the human exploration and settlement of the planet Mars. It was founded by Robert Zubrin and others in 1998 and attracted the support of notable science fiction writers and filmmakers, including Kim...

. 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. Another group is MarsDrive
MarsDrive
MarsDrive, founded in 2005, is an international non-profit space organization with a worldwide membership and branches across North America, Europe and Australasia...

, which is dedicated to private initiatives for the exploration and settlement of Mars.

Concerns

Besides the general criticism of human colonization of space (see space colonization
Space colonization
Space colonization is the concept of permanent human habitation outside of Earth. Although hypothetical at the present time, there are many proposals and speculations about the first space colony...

), 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.
  • 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
    Life on Mars
    Scientists have long speculated about the possibility of life on Mars owing to the planet's proximity and similarity to Earth. Fictional Martians have been a recurring feature of popular entertainment of the 20th and 21st centuries, but it remains an open question whether life currently exists on...

    .
  • 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 practice for future manned missions to Mars. However, in several ways experience gained on the moon would not be applicable to the task of colonizing Mars. The moon has no atmosphere, no analogous geology
    Geology
    Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...

     and a much greater temperature range and rotational period. These differences mean that Mars has more in common with Earth than Earth has with the Moon. Antarctica or desert areas of Earth provide much better training grounds at vastly lesser cost. Also, the Moon is extremely poor in several of the key elements required for life, most notably hydrogen, nitrogen and carbon (50 – 100 ppm), and has only 47.2% of the delta-v requirement for launching to orbit that Mars has.
  • 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
    Mars Gravity Biosatellite
    The Mars Gravity Biosatellite was a project initiated in 2001 by the Mars Society and volunteer students and staff of MIT to build a spacecraft to study the effects of Mars-level gravity on mammals. On 24 June 2009, a status report was released declaring the end of this program, due to lack of...

     experiment was due to become the first experiment testing the effects of partial gravity, artificially generated at 0.38 g
    G-force
    The g-force associated with an object is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces acting on an object free to move. The accelerations that are not produced by gravity are termed proper accelerations, and...

     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
    Escape velocity
    In physics, escape velocity is the speed at which the kinetic energy plus the gravitational potential energy of an object is zero gravitational potential energy is negative since gravity is an attractive force and the potential is defined to be zero at infinity...

     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. 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.
  • Mars has dust storms which can reduce solar power. The largest of these storms can cover much of the planet.

In fiction

A few instances in fiction provide detailed descriptions of Mars colonization. They include:
  • Aria
    ARIA (manga)
    is a utopian science fantasy manga by Kozue Amano. The series was originally titled when it was published by Enix in the magazine Monthly Stencil, being retitled when it moved to Mag Garden's magazine Comic Blade. Aqua was serialized in Stencil from 2001 to 2002 and collected in two tankōbon volumes...

    by Kozue Amano
    Kozue Amano
    is a female Japanese manga artist. She is widely known as the creator of Aria, which proved to be a best-selling hit, and was adapted into an anime television series consisting of 3 seasons and an OVA....

  • Axis
    Axis (novel)
    Axis is a science fiction novel by author Robert Charles Wilson, published in 2007. It is a direct sequel to Wilson's Hugo Award-winning Spin, published two years earlier. The novel was a finalist for the 2008 John W...

    by Robert Charles Wilson
    Robert Charles Wilson
    Robert Charles Wilson is an American-Canadian science fiction author.Wilson was born in the United States in California, but grew up near Toronto, Ontario. Apart from another short period in the early 1970s spent in Whittier, California, he has lived most of his life in Canada, and in 2007 he...

  • Icehenge
    Icehenge
    Icehenge is a science fiction novel by Kim Stanley Robinson.Though it was published almost ten years before Kim Stanley Robinson's acclaimed Mars trilogy and takes place in a different version of the future, Icehenge contains elements that should be familiar to readers of the Mars series...

    (1985), the Mars trilogy
    Mars trilogy
    The Mars trilogy is a series of award-winning science fiction novels by Kim Stanley Robinson that chronicles the settlement and terraforming of the planet Mars through the intensely personal and detailed viewpoints of a wide variety of characters spanning almost two centuries...

     (Red Mars, Green Mars, Blue Mars, 1992–1996), and The Martians
    Mars trilogy
    The Mars trilogy is a series of award-winning science fiction novels by Kim Stanley Robinson that chronicles the settlement and terraforming of the planet Mars through the intensely personal and detailed viewpoints of a wide variety of characters spanning almost two centuries...

    (1999) by Kim Stanley Robinson
    Kim Stanley Robinson
    Kim Stanley Robinson is an American science fiction writer known for his award-winning Mars trilogy. His work delves into ecological and sociological themes regularly, and many of his novels appear to be the direct result of his own scientific fascinations, such as the fifteen years of research...


  • First Landing
    First Landing
    First Landing is a 2002 science fiction novel by Robert Zubrin that tells the story of the first manned space expedition to Mars. Zubrin is the head of the Mars Society, an organization lobbying the real world NASA to send astronauts to Mars...

    (2002) by Robert Zubrin
    Robert Zubrin
    Robert Zubrin is an American aerospace engineer and author, best known for his advocacy of the manned exploration of Mars. He was the driving force behind Mars Direct—a proposal intended to produce significant reductions in the cost and complexity of such a mission...


  • Man Plus
    Man Plus
    Man Plus is a 1976 science fiction novel by Frederik Pohl. It won the Nebula Award for Best Novel in 1976, was nominated for the Hugo and Campbell Awards, and placed third in the annual Locus Poll in 1977. Pohl teamed up with Thomas T. Thomas to write a sequel, Mars Plus, published in 1994.-Plot...

    (1976) by Frederik Pohl
    Frederik Pohl
    Frederik George Pohl, Jr. is an American science fiction writer, editor and fan, with a career spanning over seventy years — from his first published work, "Elegy to a Dead Planet: Luna" , to his most recent novel, All the Lives He Led .He won the National Book Award in 1980 for his novel Jem...

  • We Can Remember It for You Wholesale
    We Can Remember It for You Wholesale
    "We Can Remember It for You Wholesale" is a novelette by Philip K. Dick first published in The Magazine of Fantasy & Science Fiction in April 1966. It features a classic meshing of reality, false memory and real memory...

    (1990), by Philip K. Dick
    Philip K. Dick
    Philip Kindred Dick was an American novelist, short story writer and essayist whose published work is almost entirely in the science fiction genre. Dick explored sociological, political and metaphysical themes in novels dominated by monopolistic corporations, authoritarian governments and altered...

  • Mars (1992) and Return to Mars
    Return to Mars
    Return to Mars is a science fiction novel by Ben Bova. This novel is part of the Grand Tour series of novels. It was first published in 1999 and is a sequel to Ben Bova's novel Mars.-Plot summary:...

    (1999), by Ben Bova
    Ben Bova
    Benjamin William Bova is an American science-fiction author and editor. He is the recipient of six Hugo Awards for Best Professional Editor for his work at Analog Science Fiction in the 1970's.-Personal life:...

  • Climbing Olympus (1994), by Kevin J. Anderson
    Kevin J. Anderson
    Kevin J. Anderson is an American science fiction author with over forty bestsellers. He has written spin-off novels for Star Wars, StarCraft, Titan A.E., and The X-Files, and with Brian Herbert is the co-author of the Dune prequels...

  • Red Faction
    Red Faction
    Red Faction is a first-person shooter video game developed by Volition, Inc. and published by THQ. It was released for the PlayStation 2, Microsoft Windows and Mac in 2001. A version for the Nokia N-Gage was developed by Monkeystone Games. The game was also re-developed as a top-down shooter for...

    (2001), developed by Volition
    Volition
    Volition may refer to:*Volition , the cognitive process by which an individual decides on and commits to a particular course of action...

    , published by THQ
    THQ
    THQ Inc. is an American developer and publisher of video games. Founded in 1989 in the United States, the company develops products for video game consoles, handheld game systems, as well as for personal computers and wireless devices...

  • The Platform (2011) by James Garvey
  • "The Destruction of Faena" (1974) by Alexander Kazantsev
    Alexander Kazantsev
    Alexander Petrovitch Kazantsev was a popular Soviet science fiction writer and ufologist.-Biography:Born in Akmolinsk, Imperial Russia . He graduated from Tomsk Polytechnic University, and worked in Soviet Research institute of Electromechanics. Kazantsev was a member of Soviet delegation at the...

  • "The Martian Chronicles
    The Martian Chronicles
    The Martian Chronicles is a 1950 science fiction short story collection by Ray Bradbury that chronicles the colonization of Mars by humans fleeing from a troubled and eventually atomically devastated Earth, and the conflict between aboriginal Martians and the new colonists...

    " (1950) by Ray Bradbury
    Ray Bradbury
    Ray Douglas Bradbury is an American fantasy, horror, science fiction, and mystery writer. Best known for his dystopian novel Fahrenheit 451 and for the science fiction stories gathered together as The Martian Chronicles and The Illustrated Man , Bradbury is one of the most celebrated among 20th...


Further reading


External links

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