Lunar and Planetary Institute

Apollo 17 Mission

Science Experiments - Ultraviolet Spectrometer

The Ultraviolet Spectrometer Experiment was performed on Apollo 17 to measure the density and composition of the tenuous lunar atmosphere by observing how the atmosphere scattered solar ultraviolet radiation. This experiment was sensitive to the presence of atomic and molecular hydrogen, atomic oxygen, atomic nitrogen, carbon, carbon monoxide, carbon dioxide, and xenon. Molecular hydrogen was detected at an abundance of 6000 atoms per cubic centimeter. All other species were not detected at the limits of the instrument's capability. The spectrometer could not detect helium, neon, and argon, all of which are also thought to be present in the lunar atmosphere.

Transient brightening events of the crater Aristarchus as seen on Earth have led to suggestions that outgassing sometimes occurs there, but no such release of gas was seen with this spectrometer. A transient atmosphere was detected after the Lunar Module completed its descent, but this disappeared within a few hours as the rocket exhaust gases dissipated. During the return back to Earth, the UV spectrometer was used to study a number of astronomical targets, including Earth, the Milky Way Galaxy, and selected stars.