BOB HIRSHON (host):
The surprising origin of Mercury. I’m Bob Hirshon and this is Science Update.
Mercury is a tiny planet with a huge iron core compared with the other inner planets. Patrick Peplowski is a research scientist at the Johns Hopkins Applied Physics Laboratory:
PATRICK PEPLOWSKI (Johns Hopkins Applied Physics Laboratory):
And this is a bit of a puzzling challenge, because you have to ask yourself what formation process could have made Mercury have such a different composition than the other terrestrial planets?
It was thought that Mercury started out like the other planets, and then a catastrophe—maybe a meteor impact– stripped away its outer layers. But a discovery made by the MESSENGER spacecraft, reported in the journal Science, has blasted that theory out of the sky. MESSENGER’s Gamma Ray Spectrometer found large amounts of potassium on Mercury—an element that wouldn’t survive that catastrophic scenario. The scientists now suspect the planet formed from material similar to that found in iron-rich meteors. But why Mercury formed so differently from the other rocky planets is a mystery. I’m Bob Hirshon, for AAAS, the science society.