[P-PS09] Lunar Science and Exploration

[PPS09-07] Temperature dependence of the dielectric constant on the lunar surface: Insights from Mini-RF and Diviner observations

*Chenhao Sun¹, Hideaki Miyamoto¹, Makito Kobayashi¹ (1.The University of Tokyo)

Keywords:lunar surface, dielectric constant, temperature dependence, Mini-RF, Diviner

Studying the water ice on the lunar surface is crucial not only for unraveling the evolution of the Moon and Earth but also for securing the resources to make future long-term exploration missions sustainable. Various observations have suggested that the water ice exists on the lunar surface, but the abundance and accumulation of water ice up to the depth of a few meters, which would be a target for future in-situ resource utilization, is not yet revealed in detail. Radar observation is an effective way to understand subsurface structures at this depth in terms of the dielectric constant, whose controlling factors include chemical composition, packing density, and the water/ice content. Recently, laboratory measurements have shown that the dielectric constant of lunar regolith simulants also depends on the temperature, which has never been evaluated from remote-sensing data. Here we estimate the dielectric constant from the Miniature Radio Frequency (Mini-RF) data on a lunar crater floor in the north polar region at two different local times (i.e., different surface temperatures). We calculate the dielectric constant by using the inversion method and obtain the surface bolometric brightness temperature from the Diviner Lunar Radiometer Experiment (Diviner) data. We confirm that the dielectric constant of the lunar regolith exhibits temperature dependence in the lunar environment, which agrees with the experimental result. This outcome reveals that the temperature dependence of the dielectric constant should be considered when interpreting radar observations of the Moon and other celestial bodies with large surface temperature differences.