^1,2,3C. J. Gimar et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009304]
¹Department of Physics and Astronomy, Univeristy of Texas at San Antonio, San Antonio, TX, USA
²Center for Laboratory Astrophysics and Space Science Experiments (CLASSE), Space Science Division, Southwest Research Institute, San Antonio, TX, USA
³Space Science Division, Southwest Research Institute, San Antonio, TX, USA
Published by arrangement with John Wiley & Sons

Building on our previous studies of the far-ultraviolet (FUV) reflectance of Apollo soil 10084 and lunar soil simulants JSC-1A and LMS-1 (Gimar et al., 2022, https://doi.org/10.1029/2022je007508; Raut et al., 2018, https://doi.org/10.1029/2018je005567), we present new FUV results for Apollo soils 68501 and 71061. Heavily weathered soils (68501, 10084)–enriched in submicroscopic Fe, agglutinates, and sub-micron scale roughness as revealed by our electron microscopy investigations–are darker in the FUV and predominantly backscatter incident light. In contrast, the relatively less weathered subsurface 71061 soil is approximately twice as bright, exhibits forward scattering, and presents a steeper blue spectral slope between 130 and 160 nm compared to the weathered soils. Differences in either primary composition or mineralogy appear to have little to no effect on the FUV albedo or scattering behavior of these soils since the reflectance of high-Ti mare 10084 and low-Ti highland 68501 are nearly indistinguishable within error. Further investigation of additional Apollo-era soils across various maturity indices is needed to fully characterize the influence of space weathering on lunar soil FUV spectrophotometric response.