Microscopy and Microanalysis | 2021
STEM-EELS-EDS Analysis of Space Weathering Features of ANGSA Lunar Soil Samples
Abstract
Introduction: Space weathering refers to processes that alter the surfaces of airless bodies exposed to the harsh environment of outer space. On the Moon, solar wind irradiation and micrometeorite bombardment are the dominant space weathering processes. These processes alter the surfaces of individual regolith grains, often producing thin (< 200 nm) amorphous rims that can be enriched in vesicles, nanophase metallic iron inclusions (npFe 0 ), or a combination of these [1-3]. The roles of exposure history, mineral composition, and crystal structure in the formation of amorphous rims are not well constrained. To address these gaps in understanding, lunar soil samples were analyzed with scanning transmission electron microscopy (STEM), energy dispersive spectroscopy (EDS), and electron energy loss spectroscopy (EELS) to evaluate the systematic differences in rim characteristics as a function of exposure history and mineralogy at the individual grain scale. These efforts are part of the Apollo Next Generation Sample Analysis (ANGSA) initiative examining special samples returned during the Apollo Program that have been stored under unique conditions and remain unexamined.