One of the biggest challenges for any spacecraft to overcome is Earth's gravity. As a result, leaving Earth requires a huge amount of fuel. This could be solved by building a base on the Moon, which has a much weaker gravity, thereby facilitating cheaper travel to other objects in the Solar System. The Moon could act as a staging post from which the human colonisation of the Solar System could be achieved, opening the way to vast mineral riches and potentially other homes for humans.
The most promising location for a Moonbase is on a crater rim at the lunar South Pole, such as that of Shackelton Crater, which lies directly over the axis of the Moon. This is because this region receives sunlight year-round, allowing for a constant supply of solar energy. In contrast, a Moonbase elsewhere would have to cope with the half-month long lunar night, during which time energy might run out. Moreover, the crater rim shields the interior of the crater from sunlight throughout the year, cooling it enough that ice is present. Early colonists could extract this water for use, and by attempting to recycle water as much as possible, could prolong its use.
The Moon's reduced gravity does have downsides for the long-term health of the colonists; as on the ISS, the astronauts will have to exercise for several hours a day in order to remain healthy. Even with exercise, astronauts on the ISS often face severe loss of bone density and have intensive therapy after returning back to Earth. As a result, the colonists may not be able to remain on the Moon for years at a time and may have to return after just a year.
After formation, the Moon was believed to have a strong magnetic field of approximately 110 microteslas (stronger than Earth's current magnetic field, which ranges between 30 microteslas at the equator to 60 microteslas at the poles). However, the Moon has a radius approximately 3.7x smaller than Earth's, and therefore its much smaller core cooled more quickly, to the point of solidification around 3.5 billion years ago. This means that the Moon is no longer shielded from cosmic radiation.
The largest source of cosmic radiation on the Moon is from the Sun. The Sun emits a vast quantity of charged particles (mostly protons and electrons), which are deflected by Earth's magnetic field. On bodies that lack an atmosphere, like the Moon and Mars, the solar wind interacts with their atmosphere, slowly removing it. The particles most prone to loss are ions, which are accelerated by the magnetic field of the solar wind away from the surface and into space. As a result, the Moon has an atmospheric pressure of roughly 3*10^-15 atm, or approximately 3 quadrillionths that of Earth's. Due to the lack of a magnetic field or atmosphere, the astronauts will be subject to much higher doses of radiation than on Earth. This leads to an increased risk of cancer, and potential radiation poisoning (check out my blog post on radiation poisoning for more details). As a result, more advanced spacesuits will need to be created, as these astronauts may be exposed to high levels of radiation for years on end. Lunar habitats will also need to be appropriately shielded, to ensure the safety of the astronauts.
The ice on the lunar south pole is important for more than just drinking and growing crops. Currently, rocket fuel is mostly composed of liquid hydrogen and oxygen. This can be easily obtained by electrolysis of water, allowing the Moonbase to create its own fuel, another step towards self-sufficiency. This would allow it to send rockets out to other planets for a fraction of the cost on Earth. This is especially important as rockets sent from Earth are incredibly inefficient; almost all of the weight of the rocket is made up of propellant and boosters designed to allow the rocket to leave Earth's gravity, meaning that a tiny cargo requires a massive investment of materials to be sent to space. In contrast, the Moon's gravity is much lower, so much less fuel is needed for each tonne of cargo, allowing smaller and cheaper rockets to be built.
Helium-3 is much more prevalent on the Moon than on Earth. Currently, the reserves available to us are very small, with some estimates stating that the quantity of helium-3 in the United States is only about half a tonne. As a result, there has not been much research into fusion involving helium-3, but it could either be fused with deuterium, resulting in the creating of helium-4 and a proton, which is much easier to contain (using a magnetic field) than the neutrons created by tritium fusion, which collide with the walls of the reactor, damaging parts and causing them to need to be replaced. Alternately, fusion using helium-3 entirely could be achieved, which would negate the need for deuterium to be brought from Earth, again making the colony more self-sufficient. This would partially remove the need for complete reliance on solar power, allowing colonists to spread out across the Moon, away from the south pole.
The most probable reason as of now for lunar exploration is not scientific discovery, but the potential exploitation of mineral resources on the Moon. With the ongoing privatisation of the space race, it is likely that the first Moonbase to be created will not be created by a country, but by a company. These companies will be eager to begin the extraction of mineral resources in order to make a profit on their sizeable investment. Pyroclase feldspar, the most common mineral on the Moon, contains aluminium, which would be very important in creating a base on the Moon. Iron and titanium can also be mined, from the mineral ilmenite, which is 5-8% titanium, again helping with building a Moonbase and rockets for interplanetary exploration. Unfortunately, ilmenite is concentrated in the flood basalts of the north, and so extraction would be challenging, with another fuel source apart from solar power, such as fusion, being necessary for exploration there. Silicon and calcium are present in pyroclase feldspar and could be used to create solar panels, allowing the colony to expand by itself. Using the silicon and oxygen found in pyroclase feldspar, glass could easily be created. This could then be mixed with the lunar regolith to create a form of concrete called "lunarcrete", again useful for building materials. Due to the lower gravity, asteroid mining could be facilitated, potentially earning these companies trillions of dollars from extracting elements in short supply. Gold, lead, phosphorus and many others are beginning to run out, and asteroid mining may be a short-term solution to this shortage before a more permanent solution can be found.
The mining of space resources is also being legalised in many countries. In 2015 the International Institute of Space Law declared that "the use of space resources is permitted". This was soon followed by a law in the US that legalised space mining, allowing many private space exploration companies to mine, such as SpaceX and BlueOrigin. This, along with laws passed in many other countries, makes space mining a possibility in the near future.
Overall, building a Moonbase is possible with current technology, and slight improvements in technology, such as fusion, would enable colonies to be set up across the Moon's surface. Moreover, such as base would make the creation of bases further afield easier, such as on Mars. Next time, I'll be covering the viability of hydrogen-powered cars, a prospect for the not-so-far future.
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