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New findings expand Apollo observations of lunar atmosphere

Date:
July 16, 2012
Source:
American Geophysical Union
Summary:
In December 1972 the astronauts of Apollo 17 -- the last manned mission to the moon -- deployed the Lunar Atmospheric Composition Experiment (LACE), a spectrometer designed to measure and characterize the thin lunar atmosphere. Forty years later, researchers built upon those initial measurements, providing the first remotely-sensed measurement of the Moon's gaseous environment from lunar orbit.
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In December 1972 the astronauts of Apollo 17 -- the last manned mission to the moon -- deployed the Lunar Atmospheric Composition Experiment (LACE), a spectrometer designed to measure and characterize the thin lunar atmosphere. Forty years later, Stern et al. built upon those initial measurements, providing the first remotely-sensed measurement of the Moon's gaseous environment from lunar orbit.

Using the Lyman Alpha Mapping Project's (LAMP's) far ultraviolet spectrograph aboard the Lunar Reconnaissance Orbiter, the authors determined the atmospheric concentration of helium.

By angling LAMP's sensors towards the lunar limb and comparing those observations against measurements of the interstellar background, the authors were able to estimate the helium concentration of the near-surface lunar environment. They calculate a density of 7,000 atoms per cubic centimeter at 120 degrees Kelvin (-244 degrees Fahrenheit), the assumed atmospheric temperature. The previous LACE observations ranged between 10,000 -- 20,000 and 50,000 atoms per cubic centimeter depending on the time of day, increasing at nighttime and decreasing during the day. The nighttime decrease occurs because the atmosphere cools and contracts, yielding an increased density.

The authors suggest that the next steps should involve looking for spatial or temporal variations in lunar atmospheric helium. Such observations could help to determine whether the helium is produced locally by radioactive decay of lunar material or if it is formed from trapped and neutralized solar wind.


Story Source:

The above story is based on materials provided by American Geophysical Union. Note: Materials may be edited for content and length.


Journal Reference:

  1. S. A. Stern, K. D. Retherford, C. C. C. Tsang, P. D. Feldman, W. Pryor, G. R. Gladstone. Lunar atmospheric helium detections by the LAMP UV spectrograph on the Lunar Reconnaissance Orbiter. Geophysical Research Letters, 2012; 39 (12) DOI: 10.1029/2012GL051797

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American Geophysical Union. "New findings expand Apollo observations of lunar atmosphere." ScienceDaily. ScienceDaily, 16 July 2012. <www.sciencedaily.com/releases/2012/07/120716214411.htm>.
American Geophysical Union. (2012, July 16). New findings expand Apollo observations of lunar atmosphere. ScienceDaily. Retrieved May 27, 2015 from www.sciencedaily.com/releases/2012/07/120716214411.htm
American Geophysical Union. "New findings expand Apollo observations of lunar atmosphere." ScienceDaily. www.sciencedaily.com/releases/2012/07/120716214411.htm (accessed May 27, 2015).

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