He bulge revealed: He and CO2 diurnal and seasonal variations in the upper atmosphere of Mars as detected by MAVEN NGIMS
AffiliationUniv Arizona, Lunar & Planetary Lab
Univ Arizona, Dept Planetary Sci
MetadataShow full item record
PublisherAMER GEOPHYSICAL UNION
CitationHe bulge revealed: He and CO2 diurnal and seasonal variations in the upper atmosphere of Mars as detected by MAVEN NGIMS 2017 Journal of Geophysical Research: Space Physics
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AbstractAnalysis of the Neutral Gas and Ion Mass Spectrometer (NGIMS) on the Mars Atmosphere Volatiles and EvolutioN (MAVEN) spacecraft closed source data from all orbits with good pointing revealed an enhanced Helium [He] density on the nightside orbits and a depressed He density on the dayside by about a factor of 10-20. He was also found to be larger in the polar regions than in the equatorial regions. The northern polar winter nightside He bulge was approximately twice that of the northern polar summer nightside bulge. The first 6 weeks of the MAVEN prime mission had periapsis at high latitudes on the nightside during northern winter, followed by the midlatitudes on the dayside moving to low latitudes on the nightside returning to the high latitudes during northern summer. In this study we examined the NGIMS data not only in the different latitudes but sorted by solar longitude (Ls) in order to separate the diurnal or local solar time (LST) effects from the seasonal effects. The Mars Global Ionosphere-Thermosphere Model (M-GITM) has predicted the formation of a He bulge in the upper atmosphere of Mars on the nightside early morning hours (Ls =2-5h) with more He collecting around the poles. Taking a slice at constant altitude across all orbits indicates corresponding variations in He and CO2 with respect to LST and Ls and a diurnal and seasonal dependence.
Note6 month embargo; First published: 23 February 2017
VersionFinal published version
SponsorsNASA through the Mars Exploration Program