Evaluation of the thorium and uranium contents of Martian surface rock - A new interpretation of Mars-5 gamma-spectroscopy measurements
Abstract
The thorium and uranium contents of the volcanic and ancient terra formations of Mars are evaluated on the basis of Mars-5 space probe measurements of gamma radiation from the Martian surface. Gamma-ray data for two partially overlapping territories containing different proportions of the major Martian geological formations were analyzed under the assumptions that the data represent composition differences between volcanic and terra formations, or between native and weathered rock. In the first case, it is found that the thorium and uranium contents of the volcanic Martian rocks (5 + or - 2.5 and 1.1 + or - 0.8 ppm, respectively) are similar to those of many typical terrestrial and lunar basalts, while those of the terra formations (0.7 + or 0.35 and 0.2 + or - 0.14 ppm, respectively) resemble the anorthosite-norite-troctolite series of the lunar highlands and not terrestrial continental granites. In the second case, the results obtained indicate the lack of any relation between weathering and radionuclide contents, although substantial uncertainties remain and the separation of original radioactive and daughter elements by weathering may lead to errors in gamma-ray determinations of thorium and uranium contents.
- Publication:
-
Geokhimiia
- Pub Date:
- January 1981
- Bibcode:
- 1981Geokh.......10B
- Keywords:
-
- Abundance;
- Gamma Ray Spectrometers;
- Mars Surface;
- Mars 5 Spacecraft;
- Thorium;
- Uranium;
- Geomorphology;
- Lunar Rocks;
- Magnesium Sulfates;
- Spectrophotometry;
- Volcanology;
- Weathering