BBC – Future – Will we ever colonize an asteroid?

The science fiction series The Expanse is set in 200 years in the future: humans have established colonies on the Moon and Mars, and have begun to colonize the asteroid belt.

There are powerful reasons why we might want to colonize the asteroid belt, but the predominant one is mining. Unlike Earth, where precious metals tend to be buried underground, there is an abundance of metals such as gold and palladium on the surface of asteroids. But they could also be used as an advanced scientific research post.

The Asteroid Belt orbits the Sun between Mars and Jupiter, and is believed to be the rest of a planet. While the Asteroid Belt is the main source of asteroids, asteroids can be found throughout the Solar System and come in three basic types; stony, carbonaceous and metallic. They vary in size from hundreds of meters to the size of a small house.

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Companies such as Planetary Resources and Deep Space Industries are already investing in asteroid mining and could begin extraction in 2025. However, creating a settlement on an asteroid is much more complicated than simply exploiting one.

One of the main challenges will be the amount of radiation that will hit the colonies. There will be solar radiation, Jupiter's radiation belt and more of the cosmic rays. "Cosmic rays are high-energy particles, mainly protons or high-energy nuclei, they cross you and do you bad things," explains Martin Elvis of the Harvard-Smithsonian Center for Astrophysics. On Earth, our atmosphere absorbs the most dangerous rays, and a space colony would need a similar shield. "A thick layer of water or ice could be used [for protection] but it would have to be several thicknesses."

In addition to radiation, long-term exposure to zero or microgravity is harmful to the human body. "The astronauts in the ISS have to exercise for two hours every day with resistance machines and still end up with health problems because they live in zero gravity for so long," says astrophysicist Martin Elvis, an badistant professor at the State University of North Carolina. Any long-term asteroid settlement would need some form of artificial gravity to mitigate this effect, possibly by rotating the entire structure.

By the time you have managed to go beyond the orbit of Mars and enter the territory of Jupiter and Saturn, then you have to build very large collection areas to use solar energy – Alastair Reynolds, astronomer

It would also need some form of power generation. Most probes and satellites depend on solar panels for energy, but this may not be as effective for an asteroid colony. "As you move away from the Sun, you have the Law of the Inverse Square" coming into force.If you are twice as far from the Sun, then you have a quarter of the energy coming from a certain area of ​​collector panels. solar, "says science fiction author and former astronomer Alastair Reynolds. When you get beyond the orbit of Mars and into the territory of Jupiter and Saturn, then you have to build large collection areas to use solar energy, but I do not see that as a major problem. "

The ideal type of Asteroid to sediment would be carbonaceous, since they are often 10% water. "Water is quite common in space, since it is [made] of the most common elements in the universe," says Elvis. it can decompose into oxygen and hydrogen, allowing it to breathe oxygen. "The asteroid would also need to be at least 100 meters thick to provide sufficient protection against radiation.

Settlements could be buried beneath the surface of an asteroid, that would provide protection against radiation, however, extracting and excavating an asteroid is more difficult than it seems. "A lot of what we consider as asteroids are piles of debris organized You're very lax, they do not have any intrinsic structural integrity, they're not giant rocks, "Reynolds explains. "They are more than huge bubbles or gravel joined by their own gravity."

This lack of material coherence will also mean that any attempt to rotate the asteroid – to artificially generate gravity within the asteroid – would subject it to additional forces and risk its disintegration. Therefore, some mechanism will be required to improve the durability of the asteroid. "I would have to empty it without damaging the structural integrity and then turn it while making sure that the spin does not exert too much pressure on the remaining structure," says Mack.

One suggestion is to create a metal mesh or cage that surrounds the asteroid to prevent its disintegration. This is not as prohibitive as it seems, since the asteroid belt has a large number of metal asteroids with the necessary materials that could be used.

It could take months to get back and forth, so if you have an emergency, you'll have to deal with that on the asteroid – Martin Elvis, astrophysicist

Many of the challenges faced by asteroid settlements are similar to those at the base proposed lunar. Apart from gravity, the only other important difference is distance. The Moon and the ISS are comparatively close. The Moon is only 225,623 miles (361,000 km) away at its closest point, and the ISS is just inside the Earth's atmosphere. On the other hand, the asteroid belt is approximately 160 million miles (256 million km) away.

Any asteroid settlement should be a closed and self-sustaining ecosystem, since the support of the Earth will be extremely limited. "It can take months to arrive and return, so if you have an emergency, you will have to deal with it on the asteroid, you will need a lot of people, not only will it come out and have a replicator [Star Trek]," says Elvis. Even sending a message to Earth could take an hour.

The construction of a settlement on an asteroid appears to be technically feasible, but it entails significant engineering challenges. Instead, it is much more likely that asteroids can be remotely extracted by automatic systems and drones. One option to support this could be to build a base on Mars, which could be used to coordinate asteroid mining systems.

"Both Mars and the Moon are more hospitable in terms of gravity, as well as radiation protection when using existing underground tunnels," says Mack. There are already half a dozen satellites that you can use for communications and the environment has been carefully studied.

There are some asteroids that travel in elliptical orbits around the Sun, with their trajectory approaching Earth and Mars. These can be hollowed out and used as a form of transport, while protecting astronauts from radiation and reducing the need for fuel. "We already know of a dozen or more asteroids that would be easy to push into these orbits with advanced technologies within a few years," says Elvis.

There is also a proposal to build a spaceport on Phobos, which is a moon of Mars, and some consider it was once an asteroid. This spaceport could be used as a waypoint to settle later on Mars.

While planets are the preferred location for manned bases, due to their gravity and atmospheric protection, we could colonize an asteroid. However, they would not be particularly comfortable places to live. The benefits will have to overcome the enormous challenges by far.

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