We are not close to mining asteroids, but the idea is intriguing enough to cause some serious study of the potential. The idea is simple enough – our solar system is full of chunks of rock with valuable minerals. If we could make it economically viable to mine even a tiny percentage of these asteroids the potential would be immense, a game changer for many types of resources. How valuable are asteroids?

The range of potential value is extreme, but at the high end we have a large metal rich asteroid like 16 Psyche in the asteroid belt. Astronomers estimate that the iron in 16 Psyche alone is worth about $10,000 quadrillion on today’s market. By comparison the world’s current economic output is just over $100 trillion, so that’s 100,000 times the world’s annual economic output. Of course, the cost of extraction would be high and the market value would likely be dramatically affected by such a resource, but it shows the dramatic potential of mining asteroids. Some asteroids are rich in platinum-group metals or rare earths, which would be even more valuable. But even the more common carbonaceous asteroids would likely have minerals worth quadrillions.

Again, these figures are likely not the actual monetary value that would be profited from mining asteroids, but they indicate that it is very likely economically viable to do so. I am reminded of the fact that aluminum was more expensive than gold in the 19th century. Then a process for extracting and refining aluminum from dirt was found, and now it is worth about $1.30 a pound. Still the aluminum industry is worth about $300 billion today. Mining asteroids would have a similar effect on many industries.

There are two basic uses for the material mined from asteroids. The first is to provide resources for space exploration and settlement itself. It is really expensive to get things into space, and getting out of Earth’s gravity well is the vast majority of the cost. Once in Earth’s orbit, you are most of the way there (in terms of energy costs) to pretty much anywhere in the inner solar system. So extracting resources away from Earth would potentially be extremely cost-effective. The more local the better, but even mining an asteroid for material to be used on the Moon is a huge advantage over blasting material off the Earth.

Further, many asteroids, and especially comets, have water-rich minerals or frozen volatiles. Having a steady water supply is essential if we want humans to live in space. Hydrogen from water is also potentially a source of fuel (not energy, just a way of storing energy in hydrogen).

The second use is to bring valuable minerals back to Earth. For this purpose we would want to target asteroids that are already close to Earth, and even come close to our orbit. We could even potentially alter the orbit of such asteroids to keep them in an Earth-lunar orbit, or to rest near a Lagrangian point (a “valley” in the combined gravitational fields of multiple objects that keep objects in place). We could then mine them at our leisure.

Further, if we identify an asteroid whos orbit might intersect with Earth, and therefore pose a threat of strike, we could deal with it by simply mining it out of existence. Therefore we get a double benefit – we get the minerals and we eliminate a potential threat to the Earth.

Right now we are mostly studying asteroids (and mostly from studying meteorites) to determine their composition, how to identify their composition, and determine the composition of specific asteroids that might be a target for future mining. To kickstart an asteroid mining industry we would likely want to pick the lowest-hanging fruit first – which means the easiest to mine, close to Earth, and chock full of highly valuable metals. Even still, this would require a massive investment with a very long horizon before returns are realized.

But once we get a toe-hold in this industry, the potential value is so extreme it will likely take off. We need to develop the technology for mining in low gravity environments, and develop cost-effective methods for returning the ore to Earth or perhaps even refining it in space for delivery to the Moon or Mars. Technological progress over the last two decades, specifically with reusable rockets dramatically lowering the cost of getting into space, makes mining asteroids more feasible, but further technological progress is still required.

It is easy to imagine that in a few hundred years something like the Belters of The Expanse might become a reality – people living permanently in the asteroid belt, mining it for its resources. It’s also possible that the industry would be entirely robotic – why put frail humans into the harsh environment of space unless they are absolutely necessary. Robotics and AI advances have also been extensive in the last decade, and it would certainly be more cost-effective to extract resources without having the added expense of keeping people alive in space. Belters, in other words, are likely to be robots.