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Gamma Rays Can Show Us Which Asteroids Are Worth Mining

Old prospector, meet the technology that could replace you.
A two inch europium-doped strontium iodide crystal grown in the Burger Lab for use in new generation of gamma-ray spectrometers. Image: Burger Lab/Fisk University

Gamma rays are more associated with the Incredible Hulk and black holes than asteroids, but that could change thanks to research just published in SPIE Newsroom. A team from NASA JPL, Vanderbilt, Fisk, and Planetary Science Institute demonstrated the ability for a gamma ray detector to find precious resources like gold, platinum, and rare earth metals by watching cosmic rays smash into an asteroid body.


An instrument built to take advantage of this ability could one day be common on space probes, and used to find what's going on compositionally under the surface of an asteroid, planet, or moon. Such technology might also enable upstart asteroid mining companies to separate hefty asteroids full of precious minerals from the common debris of the solar system's formation.

Gamma rays, by and large, take the form of cosmic rays—powerful cosmic bursts created from the ripping apart of an atomic nuclei. They have a high frequency which makes them penetrate deeply into whatever they strike. And while the thick metal of some asteroids can protect the insides from the burst, when the surface is bombarded with cosmic rays, it gives off an invisible (to our eyes) shower of atoms, neutrons, and gamma rays with each hit.

The detector created by the team can analyze the spectra of the atomic decay given off by these collisions. Different elements give off different wavelengths of light, with different frequencies of decay particles pointing to different elements.

The team identified a recently discovered compound, europium-doped strontium iodide, as a good candidate for their detector, but cautioned that "extensive testing" is still required to demonstrate that an instrument made with such a compound could withstand the rigors of spaceflight. However, while not quite as good as previous gamma ray spectrometers, it works at warmer temperatures and at a smaller size, making it especially suited to use on spacecraft according to a press release from Vanderbilt University.

With asteroid mining just over the horizon, and congress passing an attempted circumvention of legal hurdles to space mining, it may be something we'll see in the next ten years, opening up space not just to exploration, but also to commercial exploitation. Planetary Resources, an asteroid mining company that launched a test probe earlier this summer, wants to have full scale mining by 2025.