Salt - A critical material to consider when exploring the solar system

Abstract

Salt-rich deposits may be more widespread on planetary surfaces than is generally appreciated. Remote observations, laboratory studies of meteorites, and cosmochemical constraints all point towards widespread occurrences of salts (including halides, sulfates, and (bi)carbonates) on asteroids, icy bodies, Mars, and elsewhere. We have investigated the mid-infrared (1.8-25 mu m) reflectance spectral properties of mixtures of chondritic (ordinary, enstatite and carbonaceous) meteorites with potassium bromide; a mid-infrared transmissive salt like all halides. Our results demonstrate that halide-chondrite mixtures provide spectral signatures that either reveal the presence of transmissive materials or provide evidence for highly porous regolith. Previously, the nature of the surfaces of the asteroids 624 Hektor and 21 Lutetia was inferred using a limited range of spectra from halide-chondrite mixtures. Here, we provide an extensive dataset of halide-chondrite mixtures to encompass a wider set of possible surface compositions.