A new technology will allow scientists and astro-miners to tell the glitter from the gold when studying the surface of asteroids, planets, and moons.
Researchers from Vanderbilt and Fisk Universities, both in Tennessee, have developed a new and improved gamma-ray spectrometer that is capable of detecting the different elements that make up a certain object, using very little power and without having to be cooled down to absolute zero.
Objects in space are constantly being bombarded by cosmic rays, high-energy particles that move at extremely high speeds. When cosmic rays hit the surface of asteroids, they smash apart the atoms in the top layers and produce lots of different particles and gamma-rays, an extremely energetic type of light.
A gamma-ray spectrometer registers the different intensities and wavelengths of the gamma-rays emitted, and scientists can interpret them as the signatures of different elements such as oxygen, iron, rare-earth minerals, and so on.
“Space missions to the Moon, Mars, Mercury and the asteroid Vesta among others have included low-resolution spectrometers, but it has taken months of observation time and great expense to map their elemental surface compositions from orbit,” said Professor of Astronomy Keivan Stassun from Vanderbilt University, co-author of the study, in a statement. “With our proposed system it should be possible to measure sub-surface elemental abundances accurately, and to do it much more cheaply because our sensors weigh less and require less power to operate. That is good news for commercial ventures where cost, power and launch weight are all at a premium.”
The technological breakthrough is due to the recent discovery of a new material: europium-doped strontium iodide (SrI2). This is a transparent crystal that gives off flashes of visible light when exposed to gamma-rays. The crystal makes for a very efficient detector as the light emitted by the crystal can be easily recorded and related back to the gamma-ray that caused it. Traditional methods use germanium crystals, which pulsate proportionally to the energy captured from the gamma rays.
But while using germanium is more precise, it only works if the crystal is kept at a very low temperature and thus requires bulky cryogenic machinery and a lot of electricity. The new detector instead is light, small and consumes very little power so it has the potential to be included in orbiters and landers in future space missions.
The technical details of this discovery are reported in a paper published in the Journal of Astronomical Telescopes, Instruments and Systems.
The space mining industry has grown considerably in the last few years, and with technological developments such as this and legal protection in the United States, commercial missions to asteroids are starting to look more and more plausible.
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