Phase stability and water retention of hydrous minerals in deep Mars

Abstract

Recent Mars exploration has identified traces of liquid water that once existed, suggesting that water may still be present deep underground. Since the former existence of water cannot be explained solely by dissipation to the atmosphere, hydrous minerals are also important as water reservoirs. Among them, hydrous phosphate, hydrous sulfate, and zeolite have attracted much attention as hydrogen-bearing minerals, but there is insufficient research on their phase stability in the deep Mars and their interaction with Martian atmospheric components (especially nitrogen). In this study, therefore, we focused on these candidate hydrous minerals expected to exist on Mars and evaluated their phase stability by in situ X-ray diffraction and Raman spectroscopy under high pressure. We also examined whether they adsorb nitrogen and could be water reservoirs in the Martian interior.