Lunar composition from Apollo orbital measurements

Abstract

An X-ray spectrometer carried in the Service Module of the Apollo 15 and 16 spacecraft were employed for compositional mapping of the lunar surface. The surface measurements involved observations of the intensity and characteristic energy distribution of the fluorescent X-rays produced by the interaction of the solar X-rays with the lunar surface as well as naturally occurring gamma-rays and cosmic ray produced gamma-rays. A large scale compositional map of approximately twenty percent of the lunar surface was obtained for the first time. It was possible to demonstrate differences between the highlands and the mare and to learn something about the composition of the moon's hidden side. Results obtained from the X-ray experiment and the gamma-ray experiment are consistent with those obtained from lunar sample analysis.