There’s platinum in them thar’ asteroids!
Private corporations are getting into the asteroid business – literally! The most established and best funded member of this small field is Planetary Resources, which has announced a detailed, multi-step plan to locate asteroids that are rich in either water (frozen as ice, or chemically bound in clay-like minerals) or precious metals (like gold and platinum) and mine those resources for use in space or on Earth. One of their first steps will be to build and orbit small space telescopes that will hunt for good candidates for mining. Planetary Resources recently completed a very successful Kickstarter campaign to fund the development of a small space telescope for discovering good asteroid mining targets, and is working with the Adler’s Zooniverse citizen science program to develop an “Asteroid Zoo” to help find near-Earth asteroids.
Planetary Resources’ most dramatic claim is that a single, hypothetical, “platinum rich” 500-meter (1,640 foot) wide asteroid would contain around 174 times the world’s annual output of platinum, or about 22,000 metric tons. At platinum’s current price of $1,450 per troy ounce, this would amount to an astronomical fortune of around $1 trillion! That’s an awesome prize, but there are major challenges facing the eager asteroid prospector. First, the richest concentrations of platinum are found in iron meteorites, which come from metallic asteroids; but most iron meteorites contain less than 50 parts per million of platinum. That’s a few times richer than in ores from Earth mines. However, unlike the platinum found on Earth, which is concentrated in specific minerals, asteroid platinum is essentially evenly distributed throughout the metallic component of an asteroid (and to a lesser degree in the rocky component). Thus, it is not possible to enrich the platinum ore on an asteroid using a simple mechanical process as it’s done in a mine on Earth. Instead, a more complicated procedure would be required, such as chemically dissolving the host metal and rock and precipitating out the platinum, or subjecting the raw material to repeated cycles of melting and recrystallization, separating out the precious metals. Since mining of any kind has never been attempted in space before, much less these experimental refining processes, it’s unclear how difficult or even how possible it will be to enrich asteroid ores before returning them to Earth.
That means that asteroid miners might have to retrieve not just a small amount of refined platinum, but rather a huge mass of raw asteroid material to be refined back on Earth. That will require a lot more fuel, tremendously increasing costs, and probably necessitating making your own rocket fuel in space rather than launching it off the Earth. In principle, one can make rocket fuel from water by splitting it into hydrogen and oxygen. This means that even if your final goal is mining platinum from an asteroid, you’ll probably have to start with mining water in space. That’s where the asteroid mining development really has to be focused for the foreseeable future… but that’s a story for another blog post!
Written by Dr. Mark Hammergren, astronomer at the Adler Planetarium.