In the fifties science fiction classic, The Day the Earth Stood Still, the alien visitor Klaatu is hiding out among humans after an attempt at peaceful first contact goes awry. He shows his young friend Billy a pocket full of diamonds, explaining that, in the place where he comes from, they are common stones. Could there really be a planet where diamonds are commonplace?
According to a study by University of Colorado geologist Kevin Cannon, the answer may be ‘yes’. Cannon studied data from NASA’s Messenger spacecraft, that orbited the planet Mercury for four years, and showed that its crust is rich in graphite. Graphite is familiar as the lead in pencils, and is a form of the element carbon. Cannon showed that when graphite is shocked by meteorite impacts, it is compressed into another form of carbon: diamond. Impacts would have produced about sixteen quadrillion tons of diamonds over Mercury’s history. Since diamonds reflect infrared light in a distinctive way, these diamond deposits could be detected by infrared sensors on future spacecraft orbiting the planet.
Geologists study other planets to improve our knowledge, and ultimately understand Earth better. It isn’t currently feasible to return diamonds from Mercury to Earth for sale. But, what if this doesn’t remain true in the future? The United Nations Outer Space Treaty says that the resources of other planets are the common heritage of mankind. This treaty has already been criticized by the supporters of private space companies. Klaatu, the fictional alien that came to Earth to warn humans against spreading greed and violence beyond their home world, might not be pleased.