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.
Lunar composition from Apollo orbital measurements
ConclusionThe Apollo 15 and 16 missions have been among the most successful of the Apollo missions in terms of scientific yield. The orbital experiments worked particularly well, furnishing information about the moon as well as data about the galaxy. The X-ray and gamma-ray experiments enabled us to map a relatively large part of the moon geochemically. These experiments clearly demonstrated that the moon's crust is chemically differentiated and the highlands feldspathic in character. Historically we were able to learn something about the moon's hidden face. The gamma-ray measurements showed an as yet unexplained asymmetry in the distribution of the radioactive elements K, Th and U. The alpha experiment showed an interesting increase in alpha emission in the region of Aristarchus which may perhaps indicate a still active region on the moon. Finally the galactic measurements provide some information on the behavior of Sco X-1 and Cyg X-1 on a longer time scale than had previously been observed.
Chemical analysis experiment for the Surveyor lunar mission.
An experiment has been designed to determine the chemical composition of the lunar surface on the Surveyor soft-landing science missions to the moon. The instrument utilizes the characteristic spectrums of backward-scattered α particles and protons from (α, p) reactions to establish the elements present in a sample. The instrument can determine the amounts of most elements present in rocks with a sensitivity and accuracy of about 1 atomic %. Satisfactory analyses of a variety of terrestrial samples have been obtained.