MINERAL SPECTROSCOPY REVEALS THE EVOLUTION OF PLANETARY HABITABILITY ON MARS: A CASE STUDY OF SOUTHERN HIGHLANDS SULFATES AND CHLORIDES
A regional study of Terra Sirenum, one of the few locations on Mars where nearly all classes of secondary minerals are found in regional-scale spatial proximity, reveals (1) ancient Fe/Mg smectites and carbonates in crater peaks and walls; (2) small amounts of Al-rich clays associated with sulfates in the western part of the study area (Eridania) and thick, finely layered kaolinite-bearing units throughout the northeastern Terra Sirenum that we interpret as a felsic ash unit, providing an Al source for the numerous alunite detections found in conjunction with this unit; (3) two post-dating chemically and spatially distinct sedimentary deposits. Sulfates are typically adjacent to or underneath volcanic morphologies, and almost always in deep crater basins, likely formed by upwelling groundwaters with magmatic contributions of S and acidity. Chloride deposits are related to saline chains of lakes that are present at most elevations throughout the region. Age dating to obtain oldest age bounds of 3.4-2.3 Ga reveals these are some of the youngest large-scale mineral deposits on Mars with evidence of flowing surface water extending into at least the early Amazonian.