E. Eller

TL;DR: The results indicate the existence of a differential lunar highland crust, probably feldspathic, related to the plagioclase-rich materials previously found in the samples from Apollo 11, Apollo 12, Apollo 14, Apollo 15, and Luna 16.

TL;DR: 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 to confirm the idea that the moon has a widespread differentiated crust (the highlands).

TL;DR: The Apollo 16 X-ray fluorescence experiment was similar to that flown aboard Apollo 15 as discussed by the authors except for some minor modifications the Apollo 16 experiment was the same as the Apollo 15 experiment.

TL;DR: The X-ray fluorescence spectrometer carried in the SIM bay of the command service module was employed principally for compositional mapping of the lunar surface while in lunar orbit, and secondarily, for Xray astronomical observations during the trans-earth coast as mentioned in this paper.

TL;DR: A number of experiments carried in orbit on the Apollo 15 and 16 spacecraft were used in the compositional mapping of the lunar surface as discussed by the authors, which involved measurements of secondary (fluorescent) X-rays, gamma rays, and alpha particle emissions.