The asymmetry of Nathair Facula: A volcanologicmystery on Mercury

[Introduction] Nathair Facula is the largest and most spectrally-distinct of nearly 200 ‘bright red’ spots on Mercury’s surface, most of which are accepted to be deposits from explosive volcanic eruptions. Like most of Mercury’s faculae, it hosts a central pit (in this case about 40 km wide and over 3 km deep). However the centre of this facula does not coincide with the vent, but is displaced about 20 km northwards. This poses as-yet unresolved questions about the nature of the eruption mechanism. Furthermore, the vent area is almost certainly a ‘compound vent’ (Pegg et al., 2019) within which the locus of eruption has migrated between eruptive episodes, and it is unclear how the same asymmetry could be repeatedly en-gendered and reinforced by a series of eruptions rather than averaging out to a symmetrical distribution.