On the Long-term Weathering of Airless Body Surfaces by the Heavy Minor Ions of the Solar Wind: Inputs from Ion Observations and SRIM Simulations

Abstract

Abstract The importance of solar wind minor ions heavier than alpha particles in weathering airless body surfaces is an open debate. The fundamental question at stake is whether the variety of different minor ion species, their high masses, and their high charge states may overcome their low densities in the solar wind to enable them to significantly contribute to ion weathering processes. Here, long-term effects that develop on geological timescales are investigated. To do so, the long-term averaged energy spectrum of thermal and suprathermal solar wind ions is estimated by compiling and contrasting ion measurements gathered by the Advanced Composition Explorer (ACE), Wind, Solar TErrestrial RElations Observatory (STEREO), ARTEMIS, and Mars Atmosphere and Volatile Evolution (MAVEN) missions. The long-term ion environment is then convolved with Stopping and Range of Ions in Matter simulations. Combining these data and models, we find that solar wind minor ions significantly alter airless body surfaces, as they contribute to 8%–14% of the total sputtering and create 20%–50% of atomic displacements at depths greater than 100 nm. The new approach presented in this article therefore confirms that solar wind minor ions play an important role in the ion weathering of airless surfaces throughout the solar system.