Mercury is the planet closest to our Sun, which resembles a lot our own Moon. Because of the closeness of the Sun, conditions on Mercury are challenging, but not impossible. Quite a little research has been done about Mercury, so we have to speculate a lot when thinking about colonizing the planet.
Mercury is a small planet, and its mass is only 5.5 percent of the mass of the Earth. The diameter of Mercury is around 4 900 kilometres, which is about 40 % of the diameter of the Earth. Gravity on surface of Mercury is about 38 % of the gravity on Earth, which is about the same than gravity on Mars.
Even though Mercury is a small planet, it is quite heavy when compared to its size. Mercury has a huge, liquid, which is surrounded by a silicate mantle. On top of the mantle, Mercury has a silicate crust, which has been estimated to be hundreds of kilometres high. Because of the liquid inner core, Mercury has a magnetic field, which has a strength of about 1 % of the magnetic field on Earth.
Orbit and rotation
Mercury is the closest planet orbiting the Sun. One year on Mercury lasts around 88 days, so the year is a lot shorter than on Earth. Mercury rotates around its axle slowly, synchronously with the orbital period. For every two orbits around the sun, the planet rotates around its axle three times, essentially making one Mercury day last for two years.
We still don’t know geology of Mercury very well. When observed, it resembles our Moon a lot. Mercury hasn’t probably been geologically active for a long time, which has resulted in a surface covered with craters. There are some signs of volcanoes existing at some point in history.
In the polar regions, there are areas where frozen water might be found. When colonizing Mercury, these water ice resources might come very useful. Because of the dark areas in the craters, it’s possible for frozen water to exist.
Mercury does not have a detectable atmosphere. The planet is simply too hot and small to preserve an atmosphere. There are some gases, such as hydrogen, oxygen and helium, but the amounts are insignificant when thinking about the colonization. These gases have probably drifted to Mercury with solar wind, which also eventually drifts them away.
Not having an atmosphere might also be positive thing for colonizers. Because there is no medium for the heat to transfer, the whole planet isn’t unbearably hot. Therefore, there are colder areas in shadier places.
Because Mercury doesn’t have an atmosphere, there really isn’t a climate, if we’re exact. The temperatures on Mercury can rise as high as 400 °C on day time, and can go as low as -150 °C on night. The changes follow the phases of the day. The temperatures measured at night are one of the coldest in inner planets, even though Mercury is the closest planet to the Sun.
There are interesting areas in the polar regions, where temperatures are quite stable. Temperatures in these areas are often around -100 °C. These areas might be interesting for colonizers, as it is easier to work with coldness than extreme hotness.
Traveling to Mercury requires quite a lot of energy. Because the planet is located close to the Sun, a lot of energy is required to orbit around Mercury, and not enter the Suns orbit. This is also a reason why Mercury hasn’t been explored that much.
Traveling to Mercury takes quite a while. For example, it took over six years for the MESSENGER probe to travel to Mercury, and the amount of energy required was quite large. The first colonizers should be well-equipped and trained to survive without external support, because sending it would be expensive and time consuming. Because of the travel time, the spacecraft should be well protected from the radiation.
The best location for habitats would probably be the polar regions. They are cold areas, but at least the temperatures wouldn’t be too hot. The bases could be built partially underground, which would help with temperature control and would also protect the settlers from space radiation. The bases would probably have a great resemblance with the planned moon bases.
Polar regions also have frozen ice, which is essential for human life. The ice is located in deep craters, where it could be harvested. Craters may also contain other useful substances, that can’t be found anywhere else on Mercury.
Even though closeness to the Sun causes problems, its also useful. All required energy could be harvested from solar panels. Solar power on Mercury is about six times more efficient than solar power on Earth.
Polar regions on Mercury might have high places, where the Sun never goes below the horizon. This would allow energy collection without the need to store it. We’re not exactly sure yet, if these high places exist. Finding these places would be important, as storing energy for long nights for Mercury could be extremely expensive.
Even though Mercury is located relatively close to Earth, communications are still far from instant. When the planets are on the closest position, messages will be delivered in about four minutes. At the longest distance, it takes about twelve minutes for the messages to be delivered. There are times when the Sun is between the planets, and at those times, communication wouldn’t be possible without use of satellites.
The composition of Mercury isn’t well known, but it is estimated that the soil contains at least iron, magnesium and silicon. Some sources suggest that Mercury might also have large resources of helium-3, which might be used to fuel fusion reactors in the future.
One important resource is the solar energy humans can collect on Mercury. It has been suggested, that Mercury could be used to build solar sails, and we could send them to other parts of Solar System from there.
With current technology, terraforming Mercury wouldn’t be possible, but it might happen in the future. Because there are more potential planets for terraforming in the Solar System, exact plans haven’t been made yet.
First, we should protect Mercury from strong solar winds, as the weak magnetosphere can’t protect the planet well enough. Solar winds would blow the built atmosphere away very quickly. The protection could be done with shades that would be inserted between Mercury and the Sun.
Because Mercury only has traces of gases required for life, these should be imported from elsewhere. They could be brought from gas giants, or from Venus, but with current technology this is not possible, or would be too expensive, at least.
If we were able to create an atmosphere, the slow rotation of Mercury would pose an additional problem. Even though the atmosphere would make the temperatures more stable, days would still be unbearably hot and nights unbearably cold. Ideally, we could make the planet rotate faster, but this requires huge amount of energy, and might not ever be possible. We could build solar shades and mirrors, and control the day-night cycle that way. Earth-like days would also help humans and plants to feel like home.
With current technology, terraforming Mercury is not possible. Also, because Mercury doesn’t have any resources that we couldn’t find from anywhere else, it might be economically very unfeasible. If the human population keeps growing, terraforming Mercury might become something that we can consider in the future.
The planet closest to the Sun, Mercury, is an interesting object for colonization. Mercury already has water ice and solar energy is readily available. The gravity is relatively strong, which would make it suitable for humans.
Lack of atmosphere and challenging temperatures are a problem. Because the magnetic field of the planet is quite weak, space radiation might pose a problem for the colonizers and for the terraforming efforts. Because it takes time to travel to Mercury, the first colonizers should be able to survive independently for a long time.
Mercury is an interesting object, but with these challenges, it probably won’t be one of the first objects we will be colonizing. In the distant future, however, colonizing Mercury might become reality.