Colonization of Mars
The colonization of Mars is the proposed process of establishing permanent human settlements on the planet Mars. While most colonization concepts focus on settling, colonization is a broader ethical concept. International space law has limited colonization, and national space programs have avoided it, instead focusing on human mission to Mars for exploring the planet. The settlement of Mars would require the migration of humans to the planet, the establishment of a permanent human presence, and the exploitation of local resources.
Despite the absence of crewed missions to Mars, there have been successful robotic missions to the planet. Public space agencies have explored colonization concepts, but have primarily focused on further robotic exploration of Mars and the possibility of crewed landings. Some space advocacy groups, such as the Mars Society and the National Space Society, as well as some private organizations, such as SpaceX, have promoted the idea of colonization. The prospect of settling Mars has been a recurrent theme in science fiction literature, cinema, and the arts.
Challenges to settlement include the intense ionizing radiation that impacts the Martian surface, and the fine, toxic dust that covers the planet. Mars has an atmosphere, but it is unbreathable and thin. Surface temperatures fluctuate widely, between. While Mars has underground water and other resources, conditions do not favor power production using wind and solar; similarly, the planet has few resources for nuclear power. Mars's orbit is the third closest to Earth's orbit, though far enough from Earth that the distance would present a serious obstacle to the movement of materiel and settlers. Justifications and motivations for colonizing Mars include technological curiosity, the opportunity to conduct in-depth observational research, the possibility that the settlement of other planets could decrease the probability of human extinction, the interest in establishing a colony independent of Earth, and the potential benefits of economic exploitation of the planet's resources.
Background
Terminology
of Mars differs from the crewed Mars exploration missions currently pursued by public space agencies, as they aim to land humans for exploration.The terminology used to refer a potential human presence on Mars has been scrutinized since at least the 2010s, with space colonization in general since 1977, as by Carl Sagan, who preferred to refer to settlements in space as cities instead of colonies because of the implied colonialism; the US State Department had already made clear to avoid the use of the term because of the colonialist meaning. Today, "settlement" is preferred out of similar reasons, trying to avoid the broad sociopolitical connotations of colonization.
Today, the term is most prominently used by Robert Zubrin and the SpaceX Mars colonization program, with the term Occupy Mars also being used, aspiring for an independent Mars colony, despite limiting international space law.
Mission concepts
Landers and rovers have successfully explored the surface of Mars and delivered information about conditions on the ground. The first successful lander, the Viking 1 lander, touched down on the planet in 1976.Crewed missions to Mars have been proposed, but no person has attempted to travel to the planet, and there have been no return missions. Most of the human mission concepts as currently conceived by national governmental space programs would not be direct precursors to colonization. Programs such as those being tentatively planned by NASA, Roscosmos, and ESA are intended solely as exploration missions, with the establishment of a permanent base possible but not yet the main goal. Colonization requires the establishment of permanent habitats that have the potential for self-expansion and self-sustenance. Two early proposals for building habitats on Mars are the Mars Direct and the Semi-Direct concepts, advocated by Robert Zubrin, an advocate of the colonization of Mars.
At the February 2017 World Government Summit, the United Arab Emirates announced a plan to establish a settlement on Mars by 2117, led by the Mohammed bin Rashid Space Centre.
Comparisons between Earth and Mars
Gravity and size
The surface gravity of Mars is just 38% that of Earth. Although microgravity is known to cause health problems such as muscle loss and bone demineralization, it is not known if Martian gravity would have a similar effect. The Mars Gravity Biosatellite was a proposed project designed to learn more about what effect Mars's lower surface gravity would have on humans, but it was cancelled due to a lack of funding.Mars has a surface area that is 28.4% of Earth's, which is only slightly less than the amount of dry land on Earth. Mars has half the radius of Earth and one-tenth the mass. This means that it has a smaller volume and lower average density than Earth.
Magnetosphere
Due to the lack of a magnetosphere, solar particle events and cosmic rays can easily reach the Martian surface.Atmosphere
on Mars is far below the Armstrong limit at which people can 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 30 and 100 kPa. The atmosphere is also toxic as most of it consists of carbon dioxide.This thin atmosphere does not filter out ultraviolet sunlight, which causes instability in the molecular bonds between atoms. For example, ammonia is not stable in the Martian atmosphere and breaks down after a few hours. Also due to the thinness of the atmosphere, the temperature difference between day and night is much larger than on Earth, typically around 70 °C. However, the day/night temperature variation is much lower during dust storms when little light gets through to the surface even during the day, and instead warms the middle atmosphere.
Water and climate
is scarce, with rovers Spirit and Opportunity finding less than in Earth's driest desert.The climate is much colder than Earth, with mean surface temperatures between . The lowest temperature ever recorded on Earth was 184 K in Antarctica.
Because Mars is about 52% farther from the Sun than is the Earth, the amount of solar energy entering its upper atmosphere per unit area is around 43.3% of what reaches the Earth's upper atmosphere. However, due to the much thinner atmosphere, a higher fraction of the solar energy reaches the surface as radiation. The maximum solar irradiance on Mars is about 590 W/m2 compared to about 1000 W/m2 at the Earth's surface; optimal conditions on the Martian equator can be compared to those on Devon Island in the Canadian Arctic in June. Mars's orbit is more eccentric than Earth's, increasing temperature and solar constant variations over the course of the Martian year. Mars has no rain and virtually no clouds, so although cold, it is permanently sunny. This means solar panels can always operate at maximum efficiency on dust-free days.
Global dust storms are common throughout the year and can cover the entire planet for weeks, blocking sunlight from reaching the surface. This has been observed to cause temperature drops of 4 °C for several months after the storm. In contrast, the only comparable events on Earth are infrequent large volcanic eruptions such as the Krakatoa event which threw large amounts of ash into the atmosphere in 1883, causing a global temperature drop of around 1 °C. These dust storms would affect electricity production from solar panels for long periods, and interfere with communications with Earth.
Temperature and seasons
Mars has an axial tilt of 25.19°, similar to Earth's 23.44°. As a result, Mars has seasons much like Earth, though on average they last nearly twice as long because the Martian year is about 1.88 Earth years. Mars's temperature regime is more similar to Earth's than to any other planet's in the Solar System. While generally colder than Earth, Mars can have Earth-like temperatures in some areas and at certain times.Soil
The Martian soil is toxic due to relatively high concentrations of chlorine and associated compounds, such as perchlorates, which are hazardous to all known forms of life, even though some halotolerant microorganisms might be able to cope with enhanced perchlorate concentrations by drawing on physiological adaptations similar to those observed in the yeast Debaryomyces hansenii exposed in lab experiments to increasing NaClO4 concentrations.The presence of perchlorates may form a key component of solid rocket propellant, combining with other materials via resonant acoustic mixing.
Survivability
Plants and animals cannot survive the ambient conditions on the surface of Mars. However, some extremophile organisms that survive in hostile conditions on Earth have endured periods of exposure to environments that approximate some of the conditions found on Mars.Length of day
The Martian day is close in duration to Earth's. A solar day on Mars is 24 hours, 39 minutes and 35.244 seconds.Conditions for human habitation
Conditions on the surface of Mars are closer to the conditions on Earth in terms of temperature and sunlight than on any other planet or moon, except for the cloud tops of Venus. However, the surface is not hospitable to humans or most known life forms due to the radiation, greatly reduced air pressure, and an atmosphere with only 0.16% oxygen.In 2012, it was reported that some lichen and cyanobacteria survived and showed remarkable adaptation capacity for photosynthesis after 34 days in experiments that partially simulated Martian conditions in the Mars Simulation Laboratory maintained by the German Aerospace Center. Some scientists think that cyanobacteria could play a role in the development of self-sustainable crewed outposts on Mars. They propose that cyanobacteria could be used directly for various applications, including the production of food, fuel and oxygen, but also indirectly: products from their culture could support the growth of other organisms, opening the way to a wide range of life-support biological processes based on Martian resources.
Humans have explored parts of Earth that match some conditions on Mars. Based on NASA rover data, temperatures on Mars are similar to those in Antarctica. The atmospheric pressure at the highest altitudes reached by piloted balloon ascents is similar to that on the surface of Mars. However, the pilots were not exposed to the extremely low pressure, as it would have killed them, but were seated in a pressurized capsule.
Human survival on Mars would require living in artificial Mars habitats with complex life-support systems. One key aspect of this would be water processing systems. Being made mainly of water, a human being would die in a matter of days without it. Even a 5–8% decrease in total body water causes fatigue and dizziness, and with a 10% decrease comes physical and mental impairment. A person in the UK uses 70–140 litres of water per day on average. Through experience and training, astronauts on the International Space Station have shown it is possible to use far less, and that around 70% of what is used can be recycled using the ISS water recovery systems. Similar systems would be needed on Mars but would need to be much more efficient, since regular robotic deliveries of water to Mars would be prohibitively expensive. Potential access to on-site water via drilling has been investigated by NASA.