The Lifecycle of Hollows on Mercury: An Evaluation of Candidate Volatile Phases and a Novel Model of Formation

TL;DR

This study evaluates candidate volatile phases for hollow formation on Mercury, identifying sulfur as the most likely agent, and introduces a new model where subsurface heat and solar heating drive sulfur deposit and sublimation processes.

Contribution

It presents a thermophysical model testing 57 volatiles and proposes a novel hollow formation mechanism involving sulfur-rich subsurface and surface processes.

Findings

Elemental sulfur's properties make it the most plausible hollow-forming volatile.

A new model links subsurface heat and solar heating to hollow formation.

Sulfur deposits are likely in a permafrost zone on Mercury.

Abstract

A thermophysical model was developed to test the viability of 57 candidate hollow-forming volatiles within the hollow-formation model framework of Blewett et al. (2013). We find that the thermophysical properties of elemental sulfur (S) combined with the abundance of S on Mercury, make it the most likely hollow-forming volatile explored in this study. We propose a novel model for hollow formation in which a subsurface heat source drives sulfur-rich systems that deposit volatiles (importantly, S) in the near-surface at night within a "sulfur permafrost zone", and daytime solar heating drives sublimation to form hollows.