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Temperatures near the lunar poles and their correlation with hydrogen predicted by LEND
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  • Philipp Gläser,
  • Anton Sanin,
  • Jean-Pierre Williams,
  • Igor Mitrofanov,
  • Jürgen Oberst
Philipp Gläser
Technische Universität Berlin

Corresponding Author:[email protected]

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Anton Sanin
Institute for Space Research of Russian Academy of Sciences
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Jean-Pierre Williams
University of California Los Angles
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Igor Mitrofanov
Institute for Space Research of Russian Academy of Sciences
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Jürgen Oberst
Technische Universität Berlin, Institute of Geodesy and Geoinformation Science
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Abstract

The lunar polar regions offer permanently shadowed regions (PSRs) representing the only regions which are cold enough for water ice to accumulate on the surface. The Lunar Exploration Neutron Detector (LEND) aboard the Lunar Reconnaissance Orbiter (LRO) has mapped the polar regions for their hydrogen abundance which possibly resides there in the form of water ice. Neutron Suppression Regions (NSRs) are regions of excessive hydrogen concentrations and were previously identified using LEND data. At each pole we applied thermal modeling at three NSRs and one unclassified region to evaluate the correlation between hydrogen concentrations and temperatures. Our thermal model delivers temperature estimates for the surface and for 29 layers in the sub-surface down to 2 m depth. As anticipated, we find the three south polar NSRs which are coincident with PSRs in agreement with locations of hydrogen abundance and their respective (near-)surface temperatures. Water ice is suspected to be present in the upper ≈19 cm layer of regolith. The three north polar NSRs however lie in non-PSR areas and are counter-intuitive as such that most surfaces reach temperatures that are too high for water ice to exist. However, we found that these areas offer ideal conditions for ice pumping and suggest water ice to depths down to ≈35-65 cm. These depths are observable by LEND and can, at least in part, explain the existence and shape of the observed hydrogen signal. Although we can substantiate the anticipated correlation between hydrogen abundance and temperature the converse argument cannot be made.
Sep 2021Published in Journal of Geophysical Research: Planets volume 126 issue 9. 10.1029/2020JE006598