Mars

The acid saline lake and groundwater environments seem to be an excellent terrestrial analog for many sedimentary strata on Mars. There are similarities in mineralogy,geochemistry, sedimentary textures, sedimentary structures, and diagenetic features.
 
Both the Western Australian settings and martian strata contain an unusual assemblage of minerals, including halite, gypsum, hematite, jarosite, amorphous silica, and clay minerals. These minerals suggest that Mars once had acid brines. Geochemical analyses of martian strata also includes unusually high concentrations of metals such as nickel, similar to some Western Australian acid brines. Sedimentary textures and sedimentary structures on Mars suggests that these acid brines were in the form of ephemeral surface waters. Martian diagenetic features, such as hematite concretions and displacive crystal molds, are similar to those formed by shallow acid saline groundwater below and adjacent to Western Australia acid lakes.
Mars and Western Australian strata
 
Western Australia hematite concretions