User:Robertinventor/Colonization of Mars - concerns

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Concerns
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