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Detecting Sub-Micron Space Weathering Effects in Lunar Grains with Synchrotron Infrared Nanospectroscopy
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  • Kainen L. Utt,
  • Ryan C. Ogliore,
  • Hans A. Bechtel,
  • Jeffrey Gillis-Davis,
  • Bradley L. Jolliff
Kainen L. Utt
Laboratory for Space Sciences, Department of Physics, Washington University in St. Louis, Laboratory for Space Sciences, Department of Physics, Washington University in St. Louis

Corresponding Author:[email protected]

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Ryan C. Ogliore
Laboratory for Space Sciences, Department of Physics, Washington University in St. Louis, Laboratory for Space Sciences, Department of Physics, Washington University in St. Louis
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Hans A. Bechtel
Advanced Light Source Division, Lawrence Berkeley National Laboratory, Advanced Light Source Division, Lawrence Berkeley National Laboratory
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Jeffrey Gillis-Davis
Washington University, St. Louis, Washington University, St. Louis
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Bradley L. Jolliff
Dept. Earth and Planetary Sciences, Dept. Earth and Planetary Sciences
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Abstract

Space weathering processes induce changes to the physical, chemical, and optical properties of space-exposed soil grains. For the Moon, space weathering causes reddening, darkening, and diminished contrast in reflectance spectra over visible and near-infrared wavelengths. The physical and chemical changes responsible for these optical effects occur on scales below the diffraction limit of traditional far-field spectroscopic techniques. Recently developed super-resolution spectroscopic techniques provide an opportunity to understand better the optical effects of space weathering on the sub-micrometer length scale. This paper uses synchrotron infrared nanospectroscopy to examine depth-profile samples from two mature lunar soils in the mid-infrared, 1500–700 cm-1 (6.7–14.3 μm). Our findings are broadly consistent with prior bulk observations and theoretical models of space weathered spectra of lunar materials. These results provide a direct spatial link between the physical/chemical changes in space-exposed grain surfaces and spectral changes of space-weathered bodies.
Sep 2021Published in Journal of Geophysical Research: Planets volume 126 issue 9. 10.1029/2021JE006921