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Title: Limits to the lunar atmosphere

Abstract

The presence of sodium and potassium on the Moon implies that other more abundant species should be present. Volatile molecules like H{sub 2}O are significantly more abundant than sodium in any of the proposed external atmospheric sources. Source mechanisms which derive atoms from the surface should favor abundant elements in the regolith. It is therefore puzzling that the Apollo ultraviolet spectrometer experiment set limits on the density of oxygen of N{sub O} < 5 {times} 10{sup 2} cm{sup {minus}3}, and that the Apollo Lunar Atmospheric Composition Experiment data imply N{sub O} < 50 cm{sup {minus}3} above the subsolar point. These limits are surprisingly small relative to the measured value for sodium. A simple consideration of sources and sinks predicts significantly greater densities of oxygen. It is possible but doubtful that the Apollo measurements occur ed during an epoch in which source rates were small. A preferential loss process for oxygen on the darkside of the Moon is considered in which ionization by electron capture in surface collisions leads to escape through acceleration in the local electric field. Cold trapping in permanently shadowed regions as a net sink is considered and discounted, but the episodic nature of cometary insertion may allowmore » formation of ice layers which act as a stablized source of OH. On the basis of an assumed meteoroid impact source, the authors predict a possible emission brightness of {approximately} 50 R in the OH(A {minus} X)(0,0) band above the lunar bright limb. A very uncertain small comet source of H{sub 2}O could raise this value by more than two orders of magnitude.« less

Authors:
 [1];  [2]
  1. National Aeronautics and Space Administration, Washington, D.C. (USA)
  2. Univ. of Arizona, Tucson (USA)
Publication Date:
OSTI Identifier:
6160815
Resource Type:
Journal Article
Journal Name:
Journal of Geophysical Research; (United States)
Additional Journal Information:
Journal Volume: 96:A2; Journal ID: ISSN 0148-0227
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; MOON; SATELLITE ATMOSPHERES; APOLLO PROJECT; CHEMICAL COMPOSITION; IONIZATION; LIMITING VALUES; METEOROIDS; ORIGIN; OVERBURDEN; POTASSIUM; SODIUM; VOLATILE MATTER; WATER; ALKALI METALS; ATMOSPHERES; ELEMENTS; HYDROGEN COMPOUNDS; MATTER; METALS; OXYGEN COMPOUNDS; SATELLITES; 660000* - Physics- (1992-)

Citation Formats

Morgan, T H, and Shemansky, D E. Limits to the lunar atmosphere. United States: N. p., 1991. Web. doi:10.1029/90JA02127.
Morgan, T H, & Shemansky, D E. Limits to the lunar atmosphere. United States. https://doi.org/10.1029/90JA02127
Morgan, T H, and Shemansky, D E. 1991. "Limits to the lunar atmosphere". United States. https://doi.org/10.1029/90JA02127.
@article{osti_6160815,
title = {Limits to the lunar atmosphere},
author = {Morgan, T H and Shemansky, D E},
abstractNote = {The presence of sodium and potassium on the Moon implies that other more abundant species should be present. Volatile molecules like H{sub 2}O are significantly more abundant than sodium in any of the proposed external atmospheric sources. Source mechanisms which derive atoms from the surface should favor abundant elements in the regolith. It is therefore puzzling that the Apollo ultraviolet spectrometer experiment set limits on the density of oxygen of N{sub O} < 5 {times} 10{sup 2} cm{sup {minus}3}, and that the Apollo Lunar Atmospheric Composition Experiment data imply N{sub O} < 50 cm{sup {minus}3} above the subsolar point. These limits are surprisingly small relative to the measured value for sodium. A simple consideration of sources and sinks predicts significantly greater densities of oxygen. It is possible but doubtful that the Apollo measurements occur ed during an epoch in which source rates were small. A preferential loss process for oxygen on the darkside of the Moon is considered in which ionization by electron capture in surface collisions leads to escape through acceleration in the local electric field. Cold trapping in permanently shadowed regions as a net sink is considered and discounted, but the episodic nature of cometary insertion may allow formation of ice layers which act as a stablized source of OH. On the basis of an assumed meteoroid impact source, the authors predict a possible emission brightness of {approximately} 50 R in the OH(A {minus} X)(0,0) band above the lunar bright limb. A very uncertain small comet source of H{sub 2}O could raise this value by more than two orders of magnitude.},
doi = {10.1029/90JA02127},
url = {https://www.osti.gov/biblio/6160815}, journal = {Journal of Geophysical Research; (United States)},
issn = {0148-0227},
number = ,
volume = 96:A2,
place = {United States},
year = {Fri Feb 01 00:00:00 EST 1991},
month = {Fri Feb 01 00:00:00 EST 1991}
}