Constructional Volcanic Edifices on Mercury: Candidates and Hypotheses of Formation

Jack Wright,David A Rothery,Susan J Conway,Matthew R Balme

doi:10.1002/2017je005450

Abstract

AbstractMercury, a planet with a predominantly volcanic crust, has perplexingly few, if any, constructional volcanic edifices, despite their common occurrence on other solar system bodies with volcanic histories. Using image and topographical data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, we describe two small (<15‐km diameter) prominences with shallow summit depressions associated with volcanically flooded impact features. We offer both volcanic and impact‐related interpretations for their formation, and then compare these landforms with volcanic features on Earth and the Moon. Though we cannot definitively conclude that these landforms are volcanic, the paucity of constructional volcanic edifices on Mercury is intriguing in itself. We suggest that this lack is because volcanic eruptions with sufficiently low eruption volumes, rates, and flow lengths, suitable for edifice construction, were highly spatiotemporally restricted during Mercury's geological history. We suggest that volcanic edifices may preferentially occur in association with late‐stage, postimpact effusive volcanic deposits. The European Space Agency/Japan Aerospace Exploration Agency BepiColombo mission to Mercury will be able to investigate further our candidate volcanic edifices; search for other, as‐yet unrecognized edifices beneath the detection limits of MESSENGER data; and test our hypothesis that edifice construction is favored by late‐stage, low‐volume effusive eruptions.

Highlights

Constructional volcanic edifices, which form from the accumulation of erupted products proximal to their vent (Davidson & de Silva, 2000), have been recognized throughout the solar system (Sigurdsson et al, 2000) but have not been positively identified on Mercury
We have appraised two positive-relief landforms on the planet as candidate constructional volcanic edifices, we cannot rule out nonvolcanic hypotheses for their origins with MESSENGER data
Any small constructional volcanic edifices that do exist on Mercury likely represent only a fraction of those that ever formed, since edifices are subject to erosion, due to destruction by subsequent impacts

Summary

Introduction

Constructional volcanic edifices, which form from the accumulation of erupted products proximal to their vent (Davidson & de Silva, 2000), have been recognized throughout the solar system (Sigurdsson et al, 2000) but have not been positively identified on Mercury. The morphology of volcanic landforms reflects the style and environment of eruption, which in turn provides insight into interior processes of planetary bodies. We describe previously recognized volcanic morphologies on Mercury, before introducing two candidate constructional volcanic edifices we have identified. Mercury has abundant smooth plains, first imaged by Mariner 10, most of which are interpreted as effusive lava plains (Head et al, 2008; Strom et al, 1975). More recent imaging by the MErcury Surface, Space

Results

Discussion

Conclusion