Apollo 16 Geochemical X-ray Fluorescence Experiment: Preliminary Report
The lunar surface was mapped with respect to magnesium, aluminum, and silicon as aluminum/ silicon and magnesium/ silicon intensity ratios along the projected ground tracks swept out by the orbiting Apollo 16 spacecraft. The results confirm the observations made during the Apollo 15 flight and provide new data for a number of features not covered before. The data are consistent with the idea that the moon has a widespread differentiated crust (the highlands). The aluminum/ silicon and magnesium/ silicon concentration ratios correspond to those for anorthositic gabbros through gabbroic anorthosites or feldspathic basalts. The x-ray results suggest the occurrence of this premare crust or material similar to it at the Descartes landing site.
Chemical Analysis of the Moon at the Surveyor VI Landing Site: Preliminary Results
The alpha-scattering experiment aboard soft-landing Surveyor VI has provided a chemical analysis of the surface of the moon in Sinus Medii. The preliminary results indicate that, within experimental errors, the composition is the same as that found by Surveyor V in Mare Tranquillitatis. This finding suggests that large portions of the lunar maria resemble basalt in composition.
Chemical analysis of surfaces using alpha particles
The chemical analysis of surfaces using α-particle interactions has been investigated. Simple instruments incorporating Cm242 α sources and semiconductor silicon detectors are described. The characteristic energy spectrums of α particles scattered at large angles from thick targets of different elements have been determined. The relative intensities of scattering by different elements have been established. They show large enhancement due to nuclear effects over Rutherford scattering for elements lighter than sodium. The production of protons from (α, p) reactions in certain elements increases the sensitivity of the method for these elements. The theoretical basis for the quantitative interpretation of scattering spectrums from complex materials is developed. The technique appears to be suitable for instrumented space missions.