Mercury‘s polar deposits – origin and evolution
Final Report Abstract
In the course of this study existing software was updated to derive surface and subsurface temperatures for near-polar regions on Mercury. A digital representation of the north polar topography was created using laser altimeter data obtained by the MESSENGER spacecraft. For the topography of the south pole a digital terrain model based on stereo images was used. The terrain models were then synthetically illuminated by simulating the orbit and rotation of Mercury around the Sun. Temperature was inferred using the resulting illumination maps. The north polar temperature map was compiled for the first time using a DTM derived from the complete set of MLA tracks. During this project the very first temperature map of the south pole was derived. With the help of the illumination maps permanently shadowed regions (PSRs) could be identified. Based on the maximum surface temperature maps, areas that are always colder than 110 K could be identified. It is here, where water-ice can survive on the surface over long timescales. Last, radar observation maps were compiled which show locations with radar-bright features, which is indicative of water-ice. An additional map was created showing which parts of the poles were observed how many times by past Arecibo radar observations. The maps, i.e. the illumination, temperature and radar observation maps were fused to find locations where they agree and where they differ. It was found that there seems to be a bias in the radar observation maps rendering several craters as free of radar-bright features who might as well contain such features. Another finding was that the extent of the PSR in Prokofiev crater derived from the MLA DTM is physically plausible and the 'radar-only' area outside of the PSR can be explained by the cold sub-surface temperatures of the near-surface regolith. PSRs located below 86°N were found to be generally too hot to contain surface ice. Effective self-heating in the respective host craters was found to be responsible. Further, temperatures at 10 - 20 cm depth typically allow for water ice to be stable. This finding agrees well with previous conclusions that water ice is buried at such depths.
Publications
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Temperatures Near the Lunar Poles and Their Correlation With Hydrogen Predicted by LEND. Journal of Geophysical Research: Planets, 126(9).
Gläser, Philipp; Sanin, Anton; Williams, Jean‐Pierre; Mitrofanov, Igor & Oberst, Jürgen
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Aspects of thermal modeling using digital terrain models. Astronomy & Astrophysics, 664, A152.
Gläser, P.
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Modeling solar illumination and surface temperatures at the lunar poles, Conference ICTS on Lunar Gravitational-Wave Detection
Gläser, P.
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Modeling the thermal environment of Mercury’s north pole using MLA. Implications for locations of water ice. Icarus, 391, 115349.
Gläser, Philipp & Oberst, Jürgen
