Minerals represent potential biosignatures in the search for life on Mars
Chemical and sedimentological data indicate that reduced iron and sulfur were generated, mobilized and precipitated following the deposition of fine-grained oxidized iron- and phosphorous-bearing sediment. Except when found in authigenic nodules and reaction front rims, phosphate is not associated with a mineral phase (for example, there is no indication that apatite or merrillite are present; Fig. 4c). Accordingly, we suggest that during deposition, phosphate was adsorbed on Fe3+-, Al- and Si-r