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Dix Planetary Science Seminar

Tuesday, April 14, 2020
4:00pm to 5:00pm
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Online Event
Water on the Moon and the new Smallsat Mission Lunar Trailbl
Bethany Ehlmann, Professor, Planetary Science, Caltech,
  • Internal Event

Abstract: Water on the Moon was one of the most exciting discoveries of the late 2000's. Measured Apollo lunar glasses indicate magmas enriched in water; OH and potentially H2O were detected on the sunlit surface of the Moon by shortwave-infrared spectrometers; and the LCROSS mission impact into a permanently shadowed region (PSR) detected H2O ice, confirming inferences from a variety of remote sensing measurements and modeling. However, key questions remain. Some PSRs have water ice, while others show detections in some datasets and not others. M3 provided the best spatially-resolved (70-280 m/pixel) coverage for OH/water detection; however, because the discovery of water on the sunlit Moon was not expected, M3 was not optimized to rigorously quantify its abundance. M3's 3-μm cutoff wavelength results in ambiguities in the strength, shape, and exact position of the absorption band, which are critical for quantifying the abundance and form of hydrated species.Discrepancies exist between different thermal correction techniques, leading to conflicting results about whether the species is H2O or OH, where it is concentrated, its abundance and whether it migrates over the course of the lunar day. Lunar Trailblazer is a pioneering NASA SIMPLEx smallsat mission for understanding the Moon's water and water cycle. Selected in June 2019, the ESPA Grande ridealong Lunar Trailblazer spacecraft carries two instruments -- JPL's High-resolution Volatiles and Minerals Moon Mapper (HVM3) shortwave infrared imaging spectrometer and the UK-contributed, University of Oxford/STFC RAL Space-built Lunar Thermal Mapper (LTM) infrared multispectral imager -- that will simultaneously measure composition, temperature, and thermophysical properties from a ~100-km lunar polar orbit. Identification and characterization of water and its forms is critical knowledge as lunar exploration moves forward. This presentation will describe the key questions and mission-level design to characterize the Moon's water and geology.

For more information, please contact Shreyas Vissapragada by email at [email protected].