Far-UV Investigation of Lunar Space Weathering and Regolith Surface Properties with LRO-LAMP

As solar wind ions and micrometeorites bombard the lunar surface, they act to alter the physical properties of the regolith in a process called space weathering. Understanding the effects of space weathering is essential for interpreting the datasets returned by lunar remote sensing missions, as the observable surface layer is continuously affected by weathering from the space environment. In this study, we analyze data from the Lunar Reconnaissance Orbiter Lyman Alpha Mapping Project (LAMP) in the context of space weathering in order to characterize the effects of space weathering on the lunar surface in the far-ultraviolet (FUV). We find that regions of the lunar surface that are highly exposed to the solar wind (e.g., the equator-facing wall of South Pole crater Amundsen) display signatures of weathering in the form of high Lyman-α albedos and blue spectral slopes. Conversely, regions that are in permanent shadow are less weathered and show signatures of high porosity compared with nearby illuminated regions. We also compare the LAMP spectral slopes and FUV band ratios of a number of young rayed craters, finding that the ratios and spectral slopes decrease as exposure age increases. This result is attributed to submicroscopic iron, a by-product of the space weathering process. Finally, we perform a correction to LAMP spectral slope and band ratio maps in order remove the effects of space weathering. This correction results in new data products that will enable accurate studies of mineral composition to be made with LAMP.