Soil grains on the surfaces of airless planetary bodies such as the Moon and asteroids are continuously being modified by their exposure to interplanetary space. These surface materials experience micrometeorite bombardment and irradiation by energetic particles from the solar wind, a phenomenon collectively known as space weathering. Such interactions change the chemical and microstructural characteristics of soil grains and, as a result, their optical properties which we can measure with remote sensing spacecraft. In order to understand the nature of space weathering processes on airless planetary surfaces, I combine nanoscale analyses of returned samples with experimental simulations of space weathering in the laboratory. I will present my work using various techniques to simulate micrometeorite impacts and solar wind irradiation of both returned samples and analog materials. I will present results from a novel technique to simulate micrometeoroid impacts using in situ heating inside the transmission electron microscope (TEM). I will also describe the results of new laser and ion irradiation experiments of carbonaceous meteorites which simulate space weathering on the surfaces of organic-rich asteroids. I will explore the microstructural and chemical signatures of space weathering in these samples and their relationship to changes in optical properties of the material. Finally, I will put these experimental results in the context of ongoing planetary science sample return missions, including NASA OSIRIS-REx and JAXA Hayabusa2.
Speaker: Michelle Thompson, Purdue University
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