PIA14348: K/Th in the Inner Solar System

K/Th in the Inner Solar System


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.

Date Presented: June 16, 2011, at a NASA press conference
Instrument: Gamma-Ray and Neutron Spectrometer (GRNS)

Background Info:

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.

These images are from MESSENGER, a NASA Discovery mission to conduct the first orbital study of the innermost planet, Mercury. For information regarding the use of images, see the MESSENGER image use policy .

Cataloging Keywords:

Name Value Additional Values
Target Mercury Mars, Venus
Target Type Planet
Instrument Host MESSENGER
Host Type Orbiter
Instrument Gamma Ray and Neutron Spectrometer (GRNS)
Extra Keywords Color, Impact, Moon, Radio, Thermal
Acquisition Date
Release Date 2011-06-16
Date in Caption 2011-06-16
Image Credit NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Source photojournal.jpl.nasa.gov/catalog/PIA14348
Identifier PIA14348