Mining Asteroids

Rare Platinum Nugget
U.S. Geological Survey/photo by Chip Clark, Smithsonian

If you drive a car, chances are that it uses a catalytic converter to remove toxic compounds and reduce pollution from fuel exhaust. In order to do this, the catalytic converter uses platinum or its cousin palladium, often in combination with other precious metals such as rhodium and gold.

The metals in the platinum group (platinum, palladium, rhodium, ruthenium, iridium and osmium) have important industrial, medical and scientific applications. They are expensive, however, because their supply in the earth's crust is limited.

In contrast, some asteroids, known as M-type (M for metal), contain rich quantities of platinum and other precious metals, including gold, distributed throughout.  If such asteroids could be reached, mining those asteroids could produce a valuable payload for a returning spacecraft. Before ruling this out as economically infeasible, consider this:

Our solar system contains millions of asteroids. Most of these orbit the sun in a belt between Mars and Jupiter, but there are also near-Earth asteroids (NEAs) with orbital paths either near to or crossing the orbital path of our planet. Fifty years ago, there were fewer than 70 known NEAs. As of February 1, 2014, the IAU Minor Planet Center has cataloged over 10,000 near-Earth objects that are at least 1 meter in diameter. If one or more M-type asteroids could be captured and brought into orbit around the moon, it could be reached for mining by relatively short-haul space travel.

As tantalizing as this prospect may be, asteroids contain another substance that may prove to be even more valuable than platinum or gold. That substance is water, the stuff of life comprising 50-65% of the human body. We cannot exist for long without water. This means that, to exist for long periods in space, humans must have a source of water in space.

Water - The Stuff of Life
Photo by Tim McCabe, USDA NRCS

This is why the first asteroids to be mined are most likely to be C-type (C for carbonaceous) rather than M-type. With a water content ranging up to 20% (though ~10% appears to be more common), these asteroids could provide water to support moon bases or space platforms that would make further exploration and commercial uses of space viable. In addition, volatile compounds found in such asteroids could be used to create fuel, as could hydrogen and oxygen derived from water. This, together with solar energy, could make possible the use of materials found in asteroids to build structures in places beyond our earth. Carbon and organic materials found in asteroids might even be used to grow food. Habitats in space could become nearly or completely self-sustaining.

The future is hard to predict, but baring catastrophic setbacks (perhaps of our own making), human exploration and travel beyond the moon seems inevitable. Asteroid mining may help to pave the way.