Transformation of Ferrihydrite to Crystalline Fe Oxides in Salt Solutions: Implications for Water Chemistry on Early Mars

Abstract

Goethite, a common iron oxide formed by water reaction, is rarely found on the Martian surface. Under low temperature conditions, crystalline iron oxides are formed by the transformation of ferrihydrite, and it is known that water conditions such as pH and salinity affect the transformation of ferrihydrite. In this study, we systematically investigated the transformation behavior of ferrihydrite under a comprehensive range of water conditions, including a water chemistry of early Mars. Then, we attempted to give an indication of the rarity of goethite on Mars.