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An Experimental and Numerical Approach to Ion Sputtering of Rock Forming Minerals

Presentation #106.04D in the session Mercury (Oral Presentation)

Published onOct 23, 2023
An Experimental and Numerical Approach to Ion Sputtering of Rock Forming Minerals

Solar wind ion sputtering is a space weathering process that consistently provides high-energy particles to the exospheres of exposed bodies in space such as asteroids, moons, and planets like Mercury. Sputtering data for industrial applications have so far been explored for monoatomic species (metals, semiconductors), and some salts. Data from advanced ion sputtering simulation programs such as SDTrimSP that are based on the Binary Collision Approximation (BCA) are commonly used to compare with laboratory results. For space weathering, insulating samples significantly increase the complexity of the investigated system. Laboratory data for minerals and soils are therefore required to verify the ability of BCA programs to reproduce the sputtering behavior of planetary surfaces.

To address this problem, custom made mineral pellets were produced [1], irradiated with ion species and energies relevant for solar wind ion sputtering, and their sputter yields quantified [2]. Furthermore, a new model approach was proposed [3] that achieved unprecedented agreement with available experimental data under incidence angles of 45° and 60°. The model is solely based on fundamental mineral properties and thereby does not require any manual adjustments of simulation parameters [e.g., 4] to achieve realistic mineral densities and does not depend on computationally intensive determination of species-specific surface binding energies [e.g., 5]. In Biber et al. [2] we also successfully quantified the effect of surface roughness on the ion sputter yield by comparing sputter yields from the mineral pellets with yields from smooth thin films.

The follow-up to the new, validated sputter model will be a sputtering database (SpuBase) that includes sputter data for 21 major rock forming minerals for incidence angles ranging from 0° to 86°. The mineral-specific results are combined in SpuBase to chemically represent any soil being irradiated by hydrogen and helium ions with corresponding average solar wind energies. Future experimental data will be used to validate the modeled data. In the meantime, we aim to provide state-of-the-art yields for exosphere models for the Moon, Mercury, and other rocky airless bodies in space.

[1] Jäggi, N., et al. (2021). Icarus, 365, 114492.

[2] Biber, H., et al. (2022). Planet. Sci. J., 3, 271.

[3] Jäggi, N., et al. (2023). Planet Sci J., 4:86, 15.

[4] Szabo, P.S., et al. (2020). Astrophys. J., 891(1), 100.

[5] Morrissey, L. S., et al. (2022). Astrophys J. Lett., 925(1), L6.

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