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Modeling the influence of small-scale topography on surficial temperatures at the LCROSS impact site

Presentation #405.02 in the session Moon: Surface and Atmosphere.

Published onOct 20, 2022
Modeling the influence of small-scale topography on surficial temperatures at the LCROSS impact site

A major problem when assessing the potential stability of lunar volatiles from orbit is the limited resolution of the existing temperature data from the Diviner Lunar Radiometer, which averages over variability at small scales. It has previously been found that surface roughness on sunlit terrain at scales down to 10 cm creates “micro cold traps” – unresolved features that expand the Moon’s cold trapping area by 10-20%. Here, we expand this work into the Moon’s polar permanently-shadowed regions (PSRs) by applying illumination and thermal models to 1 metre-per-pixel rough terrain created by upscaling 240 metre-per-pixel digital elevation models (DEMs) produced by the Lunar Orbiter Laser Altimeter (LOLA). We specifically focus on the Lunar Crater Observation and Sensing Satellite (LCROSS) impact site as an opportunity to connect the observed volatile abundances in the impact plume with the modeled subpixel temperatures.

We find that small-scale roughness features create a highly-heterogeneous thermal environment that covers a wide range of temperatures, supporting the idea that temperature measurements made by Diviner are not representative of surface temperatures on human scales. Our modeled surficial cold-trapping areas are inconsistent with LCROSS abundances, suggesting a sub-surficial origin for the observed volatiles. Additionally, we investigate the seasonality of subpixel temperatures, finding that much of the LCROSS impact site experiences extended periods of extremely low temperatures, with nearly the entire Diviner/LOLA pixel remaining below 35 K for at least half of each year.

[1] Hayne, P.O., Aharonson, O., & Schörghofer, N. Micro cold traps on the Moon. Nat Astron 5, 169–175 (2021).

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