Building a Marsbase is a challenge several orders of magnitude greater than building a Moonbase, which I explored in a earlier blog post last month. Any human colony there would face elevated levels of radiation, a lack of available energy sources, muscle atrophy and bone density loss, and charged Martian dust. In addition, the distance between Mars and Earth makes travel difficult, and only a narrow window of time exists when missions to Mars can take place.
The first challenge for a settlement on Mars is finding a supply of air and water. Luckily, Mars has deposits of ice at the poles which can be harvested for water. As a result, the best location for a colony, like on the Moon, is at the poles. Hydrogen and oxygen can also be obtained by electrolysis of water. These gases can then be used as rocket fuel for more expedition, while the oxygen can be used as part of the air inside of the Martian habitats.
In order to avoid a situation similar to Apollo 1, the air should not be entirely composed of oxygen, as given ideal conditions, this could turn into a station-wide fire, destroying the base. As a result, an inert gas, such as nitrogen, is needed. Unlike on Earth, the atmosphere of Mars is only 2.7% nitrogen, and the atmosphere itself is 0.006 times as dense as on Earth, making obtaining nitrogen significantly harder. Initially, the colonists will have to bring liquid nitrogen with them to make their habitats, but this supply will slowly run out due to leakage, airlocks, and other mechanisms. Eventually, colonists will need to be able to find a source of nitrogen.
A full survey of Martian minerals has not been done yet, and so it is unknown how much nitrates there are in the Martian soil, but if they are present in reasonable quantities, then nitrogen can be obtained. Alternatively, nitrogen can be collected from the atmosphere by the same mechanism as on Earth, where air gathered is cooled to -200 degrees Celsius, and then the liquids obtained are separated by fractional distillation. This process would be much less efficient than on Earth, but could still be a viable way of obtaining nitrogen. In order to increase the yield, argon, another inert gas found in similar quantities to nitrogen in the Martian atmosphere, can also be used in the habitat atmosphere (because it's inert, it doesn't have an effect on the body, and as long as a sufficient percentage of the habitat atmosphere is oxygen, the colonists should feel no ill effects).
The next problem the colonists will face is an energy shortage. Since Mars is 1.5 AU away from the Sun (1.5 times as far away as the Earth), the light intensity is lower, meaning that solar panels are only 40% as efficient as on Earth (since the area of a sphere is proportional to the square of its radius, if the radius is increased by 1.5, the area is increased by 2.25, so the light intensity is only 1/2.25 that of Earth's, or roughly 40%). This means that much more solar panels will be needed to get the same energy input. Unfortunately, dust storms occur, with small localised dust storms happening frequently, and massive dust storms covering almost all of the planet occurring occasionally. These global dust storms can last for months, with Global Dust Storm(GDS) 2018 peaking in July and dwindling back to normal after two months. Such dust storms would render solar panels useless, meaning that the colonists would need to find another energy source to tide them over during this period, and maybe permanently.
Geothermal and wind power are not an option, as Mars' core cooled billions of years ago, and the atmosphere is not dense enough to push turbine blades. As life does not exist on Mars, no fossil fuels can be found there. This leaves nuclear energy as the only viable option. Unfortunately, uranium does not exist in high enough quantities to be used as fuel on Mars, so it would need to be imported from Earth. Luckily, uranium has a very high energy density, so this shouldn't be a big problem, as long as it's adequately shielded during transport. As a popular webcomic put it:
Mars has faced the same problem as the Moon; it was too small for its core to retain heat, and therefore it cooled, leading to a dramatic reduction in the size of the magnetic field, which exposed the Martian atmosphere to the solar wind, removing almost all of it, and further exposing the ground to radiation. Colonists unshielded on the surface would experience 22 millirads of radiation per day, or 8 rads per year. This should not be a significant problem for colonists, but still may increase cancer risk, among other effects. In order to prevent this, habitats could be shielded by covering them in a very thick layer of the Martian regolith, which should reduce the dose felt inside to normal levels.
While the effects of reduced gravity on Mars would not be as severe as those felt on the ISS or on the Moon, they would still lead to muscle atrophy and bone density loss over time, even with exercise. This would lead to significant health problems for colonists over a long time, and much worse problems for humans who were born and raised on Mars. This problem could be rectified in the future by building a rapidly spinning habitat, similar to a Stanford torus, where the edges are oriented such that the resultant force due to gravity and the change in direction is perpendicular to the surface. In this environment, people could live in 1g, and would not suffer the effects of low gravity. However, this is still very far off, and so the colonists would have to cope with low gravity, for now at least.
Much of the building of the colony would have to be done using robots, for the simple reason that electrostatically-charged dust would stick to everything that ventured out no the Martian surface. For that reason, it is more effective to have robots remain outside and do most of the function, while the humans remain inside. If they went outside, on return they would deposit the dust inside the airlock. This is especially problematic as Martian soil is roughly 0.6% perchlorate ions by mass, which prevent proper operation of the thyroid gland, leading to iodine deficiency which would cause goitres, neurodevelopmental problems, and stunted growth.
Mars also has some promise for mineral exploitation, though this would be only of help in building the colony and rockets, and not in transporting back to Earth (due to the high cost of transportation, the minerals wouldn't be economically competitive). Also problematic is that the highest concentrations of useful elements are found in flood basalts, which occur as a result of volcanic activity. One such flood basalt, the Tharsis volcanic plateau, is so massive that it has caused extensive fracturing of the lithosphere. Unfortunately, it is located near the equator, away from a good source of water, so extraction could prove difficult. This could be partially solved by extracting water from gypsum, as found in the Meridiani Planum, on the equator. Closer to the poles, iron can be easily gathered from meteorites and from the soil. The soil is also rich in aluminium and titanium, useful for building, and magnesium, which could be used to grow plants. Nitrates harvested from the soil could also be used to grow plants, along with artificial lighting.
Overall, a Marsbase would face significant challenges without much economic reward. As a result, the first Marsbase is likely to be established not through economic need, but from a desire to be the first to permanently colonise Mars. Mars may also aid the long-term survival of the human race, in the event of a cataclysmic event on Earth. For a plan on how to terraform Mars using mostly current human technology, why not read my previous blog post on the matter.
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