Environmental Effects on Space Weathered Lizardite Grains*

Small airless bodies in our Solar System are continually bombarded by ions from solar wind and micrometeorites through a process referred to as space weathering. When studying asteroids with remote sensing techniques or analyzing samples from successful sample return missions (eg. OSIRIS-REx, Hayabusa2), it is vital to understand the role of space weathering.

This study follows up on Cantando et al.'s 2008 investigation of discrepancies in the magnesium abundance found in various studies on space weathered olivine samples. Using X-Ray Photoelectron Spectroscopy (XPS), the group determined that ion-irradiated olivine was susceptible to magnesium depletion when exposed to H₂O. Here, we studied whether lizardite experiences a similar magnesium depletion effect. We performed all experiments on ~3mm grains of lizardite, which we analyzed with XPS in a PHI 5600 Surface Analysis system operating at a base pressure of ~10^-9 Torr. We irradiated samples with 4 keV He⁺ ions, then soaked them in High Performance Liquid Chromatography H₂O. We then returned the samples to the analysis chamber for final XPS analysis, so that we could determine how the Mg:Si ratio changes with varying irradiation fluence and soak time. We anticipate our results to have strong implications for how sample preparation may alter returned samples, as well as provide insight into surface characteristics that could indicate alteration from liquid water.