Synodic and Semiannual Oscillations of Argon-40 in the Lunar Exosphere

The neutral mass spectrometer on the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft collected a trove of exospheric data, including a set of high-quality measurements of radiogenic Ar-40 over a period of 142 days. Data synthesis studies, using well-established exosphere simulation...

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Bibliographic Details
Published in:Geophysical research letters 2016-01, Vol.43 (1), p.22-27
Main Authors: Hodges, R. Richard, Jr, Mahaffy, Paul R.
Format: Article
Language:English
Subjects:
Adsorption
Argon
argon‐40
Atmosphere
Atmospheric chemistry
Atmospheric particulates
Cold traps
Desorption
Dust
Dust control
Dust storms
Electric power distribution
Exosphere
Geomorphology
LADEE
Lunar And Planetary Science And Exploration
Lunar atmosphere
Lunar craft
Lunar dust
Lunar exosphere
Lunar exploration
Lunar regolith
Lunar spacecraft
Lunar surface
Mass
Moon
Oscillations
Poles
Properties
Regolith
Semiannual oscillation
Simulation
Sorption
Spacecraft
Traps
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Summary:The neutral mass spectrometer on the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft collected a trove of exospheric data, including a set of high-quality measurements of radiogenic Ar-40 over a period of 142 days. Data synthesis studies, using well-established exosphere simulation tools, show that the LADEE argon data are consistent with an exosphere-regolith interaction that is dominated by adsorption and that the desorption process generates the Armand distribution of exit velocities. The synthesis work has uncovered an apparent semiannual oscillation of argon that is consistent with temporal sequestration in the seasonal cold traps created at the poles by the obliquity of the Moon. In addition, the LADEE data provide new insight into the pristine nature of lunar regolith, its spatially varying sorption properties, and the influence of sorption processes on the synodic oscillation of the argon exosphere.
ISSN:0094-8276
1944-8007
DOI:10.1002/2015GL067293