Journal article
Understanding temporal and spatial variability of the lunar helium atmosphere using simultaneous observations from LRO, LADEE, and ARTEMIS
Icarus (New York, N.Y. 1962), Vol.273, pp.45-52
07/15/2016
DOI: 10.1016/j.icarus.2015.09.011
Abstract
Simultaneous measurements of helium in the exosphere of the Moon are made from the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) and the Lunar Atmosphere and Dust Environment Explorer (LADEE) Neutral Mass Spectrometer (NMS) through the entire 5-month span of the LADEE mission. In addition, the ARTEMIS mission monitored the solar wind alpha particle flux to the Moon. Modeling the lunar helium exosphere, we relate the LAMP polar observations to the LADEE equatorial observations. Further, using the ARTEMIS alpha flux in the Monte Carlo model reproduces the temporal variations in helium density. Comparing the LAMP data to the LADEE data shows excellent agreement. Comparing those with the ARTEMIS data reveals that the solar wind alpha flux is the primary driver to variability in the helium exosphere throughout the LADEE mission. Using a decay time for exospheric helium of 5 days, we determine that the solar wind contributes 64 +/- 5% of the helium to the lunar exosphere. The remaining 36 +/- 5% is presumed to come from outgassing of radiogenic helium from the interior of the Moon. Furthermore, the model reproduces the measurements if 63 +/- 6% of the incident alpha particles are converted to thermalized helium atoms through the interaction between the alphas and the lunar surface. However, these values are dependent on both inferred source rates from LAMP and LADEE observations and on the assumed time constant of the exospheric decay rate. (C) 2015 Elsevier Inc. All rights reserved.
Details
- Title: Subtitle
- Understanding temporal and spatial variability of the lunar helium atmosphere using simultaneous observations from LRO, LADEE, and ARTEMIS
- Creators
- Dana M. Hurley - Johns Hopkins University Applied Physics LaboratoryJason C. Cook - Southwest Research InstituteMehdi Benna - Goddard Space Flight CenterJasper S. Halekas - University of IowaPaul D. Feldman - Johns Hopkins UniversityKurt D. Retherford - Southwest Research InstituteR. Richard Hodges - University of Colorado BoulderCesare Grava - Southwest Research InstitutePaul Mahaffy - Goddard Space Flight CenterG. Randall Gladstone - Southwest Research InstituteThomas Greathouse - Southwest Research InstituteDavid E. Kaufmann - Southwest Research InstituteRichard C. Elphic - Ames Research CenterS. Alan Stern - Southwest Research Institute
- Resource Type
- Journal article
- Publication Details
- Icarus (New York, N.Y. 1962), Vol.273, pp.45-52
- Publisher
- Elsevier
- DOI
- 10.1016/j.icarus.2015.09.011
- ISSN
- 0019-1035
- eISSN
- 1090-2643
- Number of pages
- 8
- Grant note
- NNX13AO70G / NASA through LADEE Guest Investigator Program NNG05EC87C / NASA through LRO LAMP mission NASA through ARTEMIS mission NASA through the LADEE mission
- Language
- English
- Date published
- 07/15/2016
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984428681102771
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