Europa is the fourth largest moon of Jupiter, and the sixth largest moon in the Solar System. It is an interesting object for human colonization, but we have to overcome a couple of problems before we can attempt that.
Europa is slightly smaller than the Moon of the Earth, its diameter being about 3 100 kilometres. The mass of Europa is about 1 percent of the mass of the Earth. The gravity on Europa is about 13 percent of the gravity on the Earth, and we don’t have knowledge if this is large enough for long term stays.
Structurally, Europa is a lot like the inner planets, and it consists mostly of silicate rocks. Most likely it also has a core, which consists mostly of iron. In addition to rocks, it has been estimated that Europa has a huge ocean, possibly over 100 kilometres deep. The crust of the Europa would be the frozen surface of this ocean. Europa has a magnetic field, which is created in interaction with the magnetic field of Jupiter.
Orbit and rotation
Europa orbits Jupiter at an approximate distance of 671 000 kilometres. One orbit around Jupiter takes Europa around three and a half days. Europa is tidally locked to Jupiter, so the same side of Europa always faces Jupiter.
Because Europa orbits quite close to Jupiter, it is under heavy radiation caused by the radiation belts of Jupiter. This causes problems for colonization, as the settlers should be always heavily protected from radiation.
The surface of Europa consists almost solely of ice. The surface is relatively new, being only tens or hundreds of millions years old. There are no large craters. The shade of the soil varies widely because of variable composition of the ice and the other elements mixed with it. Europa is one of the smoothest objects in the Solar System.
Europa has a thin atmosphere, that consists almost solely out of oxygen. Unlike on Earth, the oxygen on Europe doesn’t stem from photosynthesis, but from heavy radiation. The atmosphere is so thin, that the people can not be outside without protective gear and oxygen masks.
Europa is a cold object because of the distance from the Sun. The average temperature is only about -170 °C. The coldest temperatures are around -220 °C, and the warmest temperatures are only about -150 °C. This causes problems for human colonziation, but the cold temperatures can be circumvented.
Traveling to Europa takes about the same time than traveling to Jupiter or to its other moons. For example, according to NASA, a round-trip to an other moon, Callisto, could be done in around four years. With advances in spacecraft technology, the trip could probably be done even faster.
Cold temperatures and high amounts of radiation cause challenges for habitats. Humans can protect from both, but they would hamper the collection of resources from Europa. According to one suggestion, we could first build a surface base. After that, we could try to find a suitable permanent location for an underground base, which would be located near the subsurface ocean. Ice would provide protection from radiation and the temperatures would be more suitable for habitats.
It could be also possible to build habitats in the subsurface ocean. Currently, humans can live in submarines for months very independently. Building these submarines will be challenging, though, unless the resources for them are brought from the Earth.
One problem for colonization would be the possible life that could be found from Europa. Because the temperatures in the sea are suitable for life, and the moon has all the necessary elements for life, the oceans could already harbour life. Therefore, colonizing the oceans would be ethically questionable, but might also pose dangers for the colonizers.
Because of the large distance from the Sun, using solar power would be challenging. We could use fission nuclear reactors, and the fuel for them could be brought from the Earth. If we are able to make fusion reactors work, the fuel from them could be brought from Jupiter.
Communication delays is very similar than to Jupiter and its other moons. At the optimal position, messages would be delivered in about half an hour. With the longest delay, it would take almost an hour for the messages to be delivered. There are times, when the communications would be hampered because Jupiter or the Sun would be between Europa and the Earth.
Europa has a lot of important resources for life, such as hydrogen and oxygen. The other resources on Europa are not well known, as we have been mostly able to observe the ice covering the planet. Its possible, that there are valuable resources under its surface, but harvesting them can be quite tricky.
There has been quite a lot of speculation about whether terraform would be an object we could terraform. Its not one of the easiest targets, but it could become possible in the future. There are problems caused by the radiation, cold temperatures and by the lack of atmosphere.
Protecting the moon from the radiation belts of Jupiter can be challenging. It would require that we create an artificial magnetic field, or that we could start the internal process in the core, that would create a magnetosphere. We do not have technology for either of these solutions. Therefore, humans could not survive on Europa without protection, but some small insects might be able to.
We could try to create an atmosphere on Europa by making oxygen and hydrogen from water. In addition to oxygen, the atmosphere would need buffer gas, such as nitrogen. We could also use heavier gases, such as argon on neon as a buffer gas. Because of the small gravity of Europa, there is a danger that the atmosphere would disappear in to the space.
Europa should also be warmed to make it hospitable for life. The best option would be to create a greenhouse effect. Strong greenhouse gases, such as ammonia and methane could be brought to Europa. Sulfur hexafluoride, a strong greenhouse gas, could also be used.
If we were able to create a suitable atmosphere and temperatures, there would still be additional problems. Because Europa has a lot of water, the whole moon could be covered by a huge ocean. Therefore, we would need to create artificial continents and islands, or try to remove the excess water. Hydrogen, that is an element in the water, could be transported to Venus to help with its terraforming process.
Europa is an object that has spurred a lot of interest. However, Europa is a challenging object for colonization. Its located quite far, it experiences strong radiation and temperatures are not suitable for humans.
We could start bases on Europa, but supporting long term habitats could be very hard, as the resources on the ocean floor can be hard to harvest. Europe could, like the other large moons, be a waypoint for exploring gas giants and remote locations in the Solar System.
Terraforming of Europa has also been discussed widely, but there are better prospects for terraforming. With technological advancements, it could become possible, but its unlikely that this is going to happen in a long while.