Impact heat driven volatile redistribution at Occator crater on Ceres as a comparative planetary process

A Neesemann,C T Russell,D Williams,P Schenk,S Marchi,J Scully,C Pieters,D O’Brien,F Tosi,B Schmidt,J Castillo-Rogez,A Nathues,H Sizemore,C Raymond,M De Sanctis,D Buczkowski

doi:10.1038/s41467-020-17184-7

Abstract

Hydrothermal processes in impact environments on water-rich bodies such as Mars and Earth are relevant to the origins of life. Dawn mapping of dwarf planet (1) Ceres has identified similar deposits within Occator crater. Here we show using Dawn high-resolution stereo imaging and topography that Ceres’ unique composition has resulted in widespread mantling by solidified water- and salt-rich mud-like impact melts with scattered endogenic pits, troughs, and bright mounds indicative of outgassing of volatiles and periglacial-style activity during solidification. These features are distinct from and less extensive than on Mars, indicating that Occator melts may be less gas-rich or volatiles partially inhibited from reaching the surface. Bright salts at Vinalia Faculae form thin surficial precipitates sourced from hydrothermal brine effusion at many individual sites, coalescing in several larger centers, but their ages are statistically indistinguishable from floor materials, allowing for but not requiring migration of brines from deep crustal source(s).

Highlights

Hydrothermal processes in impact environments on water-rich bodies such as Mars and Earth are relevant to the origins of life
lobate floor deposit (LFD) morphologies at these scales[9] and modeling of impact heating[10] suggested formation either as impact-derived deposits reminiscent of those observed in large craters on the Moon[9,11] (e.g., Tycho, Jackson) and Earth (e.g., Manicougan12,13), or as post-impact volcanic outflows from deep subsurface water-rich reservoirs[7,14,15,16], with important implications for Ceres’ internal thermal and geochemical structure
We test using XM2 stereo and Digital Elevation Models (DEM) data whether water migration and freezing led to localized frost heave and surface uplift in a manner analogous to pingos[18], whether volatile release owing to crystallization of melts occurred, and whether carbonate deposition occurred by localized brine effusion, fountaining and ballistic emplacement, and/or deposition in transient lacustrine settings[14,15,16], or by another mechanism

Summary

Introduction

Hydrothermal processes in impact environments on water-rich bodies such as Mars and Earth are relevant to the origins of life. We show using Dawn high-resolution stereo imaging and topography that Ceres’ unique composition has resulted in widespread mantling by solidified water- and salt-rich mud-like impact melts with scattered endogenic pits, troughs, and bright mounds indicative of outgassing of volatiles and periglacial-style activity during solidification. These features are distinct from and less extensive than on Mars, indicating that Occator melts may be less gas-rich or volatiles partially inhibited from reaching the surface. If Europa Clipper or the ESA Ganymede mission confirm that Callisto’s outer layers are a partially differentiated[30,31] mixture of ice and

Methods

Results

Conclusion