Mid-infrared spectroscopy of sulfidation reaction products and implications for sulfur on Mercury

Renggli, CJ; Stojic, AN; Morlok, A; Berndt, J; Weber, I; Klemme, S; Hiesinger, H

Abstract

We propose that the observed enrichment of sulfur at the surface of Mercury (up to 4 wt.%) is the product of silicate sulfidation reactions with a S-rich reduced volcanogenic gas phase. Here, we present new experiments on the sulfidation behavior of olivine, diopside, and anorthite. We investigate these reaction products, and those of sulfidized glasses with Mercury compositions previously reported, by mid-IR reflectance spectroscopy. We investigate both the reacted bulk materials as powders as well as cross-sections of the reaction products by in situ micro-IR spectroscopy. The mid-IR spectra confirm the presence of predicted reaction products including quartz. The mid-IR reflectance of sulfide reaction products, such as CaS (oldhamite) or MgS (niningerite), is insufficient to be observed in the complex run products. However, the ESA/JAXA BepiColombo mission to Mercury will be able to test our hypothesis by investigating the correlated abundances of sulfides with other reaction products such as quartz.