Composition and physics of the lunar atmosphere.The existence in the lunar atmosphere of helium, neon, argon, and possibly molecular hydrogen has been confirmed by the Apollo 17 mass spectrometer. The observed helium concentrations and distribution agree closely with model predictions for a non-condensable gas based on a solar wind source, thermal escape and a Monte Carlo random walk calculated longitudinal distribution. Heavier gases are lost by photoionization and subsequent sweeping away by the solar wind electric field. The observed nighttime neon concentration of 80,000 molecules per cu cm is consistent with expected amounts. Argon, however, is adsorbed on the lunar surface late at night when the surface temperature is lowest. It shows the expected predawn enhancement exhibited by condensable gases released into the atmosphere at the sunrise terminator. Hydrogen appears to exist in the molecular rather than atomic state. Its observed concentration is less than a factor of 3 higher than that predicted by a model similar to that used for helium.
Document ID
19730051171
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Hoffman, J. H.
Hodges, R. R., Jr.
Johnson, F. S. (Texas, University Dallas, Tex., United States)
Evans , D. E. (NASA Johnson Space Center Houston, Tex., United States)
Date Acquired
August 7, 2013
Publication Date
May 1, 1973
Subject Category
Space Sciences
Meeting Information
Meeting: Plenary Meeting on The near ultraviolet spectrum of early type stars obtained with S 59