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Detecting Sputtering and Irradiation Products of Low- and Mid-Energy Electrons on H₂O and CO₂ Ices Relevant to Icy Solar System Bodies

Presentation #109.06 in the session “Icy Satellites: Surface and Above”.

Published onOct 26, 2020
Detecting Sputtering and Irradiation Products of Low- and Mid-Energy Electrons on H₂O and CO₂ Ices Relevant to Icy Solar System Bodies

Despite electrons being a major constituent of the ionospheres, magnetospheres, and plasmas surrounding airless planetary bodies and their satellites, much of the past work investigating sputtering products on icy bodies via space weathering processes has disregarded contributions from electrons. This is largely due to the assumption that electron energy flux distributions around these bodies are dominated by > 1 keV electrons, which have low sputtering efficiencies. However, the Cassini spacecraft observed significant lower energy electron (<1 keV) fluxes at Dione and Rhea, and recent experiments have reported higher sputtering efficiencies for lower energy electrons, indicating that their importance may have been overlooked. Preliminary sputtering experiments on water ice utilizing these low- and mid-energy electrons have produced a myriad of products observed in Cassini measurements around Saturn’s moons and rings (e.g. neutral and charged H2, O2, and water clusters), the production of which has been previously attributed to UV or ion irradiation alone. In this work, H2O and CO2 ices are irradiated with 12.5 eV–2 keV electrons and yields of positively charged sputtering products as well as their kinetic energy distributions are measured via Residual Gas Analysis (RGA) and Secondary Ion Mass Spectrometry (SIMS). In addition, IR spectra are collected before and after irradiation to track chemical changes in the surface and bulk of the ices. These experiments seek to establish what positively charged species are expected to form via electron sputtering desorption on the icy surfaces of Jovian satellites, rings, and outer solar system objects as well as how low- and mid-energy electrons can alter these surfaces, aiding in the analysis of past and future surface and exosphere data of icy solar system bodies.


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