June 16, 2011, at a NASA press conference
Gamma-Ray and Neutron Spectrometer (GRNS)
This figure shows the ratio by weight of potassium to thorium for the terrestrial planets and Moon, plotted versus distance from the Sun. Because K is a volatile element and Th a refractory one, this ratio is a sensitive measure of thermal processes that fractionate elements by volatility. For example, the ratio for the Moon (360) is much lower than that for Earth (3000), reflecting volatile loss during the Moon's formation by a giant impact. The ratio for Mercury (~6000), determined by GRNS
, is comparable to that of Venus, Earth, and Mars, indicating that Mercury is not highly depleted in volatile elements, ruling out some models for its formation and early history.
The MESSENGER spacecraft is the first ever to orbit the planet Mercury, and the spacecraft's seven scientific instruments and radio science investigation
are unraveling the history and evolution of the Solar System's innermost planet. Visit the Why Mercury?
section of this website to learn more about the key science questions that the MESSENGER mission is addressing.
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
For information regarding the use of MESSENGER images, see the image use policy.