Carbon as a key driver of super-reduced explosive volcanism on Mercury: Evidence from graphite-melt smelting experiments

Mid‐Infrared Spectroscopy of Sulfidation Reaction Products and Implications for Sulfur on Mercury

“…Further evidence for low f O 2 at the surface of Mercury is the low O/Si (1.2 ± 0.1) ratio measured by Gamma‐Ray Spectrometry (Nittler et al., 2018). However, this low O/Si ratio observed at the very surface of the planet may be due to space weathering and graphite‐induced smelting reactions (Iacovino et al., 2023; McCubbin et al., 2017). Magmas and gases interacting with graphite would be buffered at the graphite‐CO buffer for f O 2 at the low‐pressure conditions on the surface of Mercury (Keppler & Golabek, 2019).…”

“…Assuming that melts on Mercury experience no oxidation from the highly reduced mantle source, sulfides in lavas on the surface of Mercury may be of primary magmatic origin (Anzures, Parman, Milliken, Namur, et al., 2020; Namur et al., 2016; Zolotov et al., 2013). However, if the magmas experienced even minor degrees of oxidation from the mantle source to the surface, the solubility of S would have decreased from approximately 7 wt.% at IW‐7, to 3 wt.% at IW‐5, and 1 wt.% at IW‐3 (Namur et al., 2016), resulting in the degassing of S. Processes that could have resulted in the oxidation of ascending magmas on Mercury include assimilation of oxides into the melts (Zolotov, 2011), decompression oxidation (e.g., Foley, 2011), or smelting processes (Iacovino et al., 2023; McCubbin et al., 2017). Previously, it was argued that such oxidation mechanisms have resulted in the formation of volcanic gases that drive explosive volcanism on Mercury (Deutsch et al., 2021; Iacovino et al., 2023; Kerber et al., 2011; Nittler et al., 2014; Weider et al., 2016), including the depletion of pyroclastic deposits in the degassed volatiles, as observed in the S depleted Nathair Facula, NE of Rachmaninov crater (Weider et al., 2016).…”

Experimental investigation of the bonding of sulfur in highly reduced silicate glasses and melts

“…Additional processes which may induce the formation of Ca or Mg sulfides at the surface of Mercury have been suggested, such as gas-solid interactions during volcanic and impact processes (Renggli et al, 2022). SiS 2 is another compound that can form during volcanic degassing at the surface of this planet (Iacovino et al, 2023).…”