Investigating The Moon's Atmosphere

WASHINGTON, D.C. -- An intensive effort is underway to determine the composition of the Moon's tenuous atmosphere. Although conventional wisdom says the Moon is devoid of atmosphere, and in layman's terms this may be close enough to the truth, the space just above the lunar surface is not a total vacuum. The Apollo program identified helium and argon atoms there, and Earth-based observations added sodium and potassium ions to the list in 1988.

Extensive searches for additional atmospheric components have been made from the lunar surface, from orbital spacecraft, and from Earth, but only about 10 percent of the density of the lunar atmosphere can be attributed to the four directly observed elements. Scientists believe that the Moon's regolith, or surface layer, is a significant source of the atmospheric sodium. They are therefore seeking to learn which other atoms the regolith may release and whether they form part of the Moon's atmosphere.

Geophysical Research Letters, a publication of the American Geophysical Union, is publishing new findings on the composition of the lunar atmosphere by a group of scientists headed by Drs. Urs A. Mall and Erhard Kirsch of the Max Planck Institute for Aeronomy in Katlenburg-Lindau, Germany.

Titled "Direct Observation of Lunar Pick-up Ions near the Moon," the GRL paper describes observations of the lunar atmosphere by the Suprathermal Ion Spectrometer (STICS) instrument aboard the WIND spacecraft. STICS has identified ions of several elements, including oxygen, silicon, and aluminum, but only in small amounts. The quality and quantity of STICS measurements will increase considerably in November 1998, when WIND will spend an extended period of time near the Moon.

In addition to the Max Planck Institute, researchers on this study are based at the Institute for Geophysics and Meteorology of the University of Cologne, Germany; the Institute for Physical Science and Technology of the University of Maryland, College Park; and the Institute for the Study of Earth, Oceans, and Space of the University of New Hampshire, Durham.

Editors: A copy of the Mall, et. al., paper, including contact information for the authors, is available on request. It has not yet been scheduled for a specific issue of GRL, but is not under embargo.