Life analog sites for Mars from early Earth: diverse habitats from the Pilbara Craton and Mount Bruce Supergroup, Western Australia

The ancient rocks of the Pilbara region of Western Australia have been an important analog site for the study of possible inhabited environments in the search for life on early Mars for over four decades. Here, we review the evidence for Paleo- to Neoarchean life and the habitats that it occupied in the Pilbara Craton and unconformably overlying Fortescue Group of the Mount Bruce Supergroup. Nine major inhabited environments are described, which range from land to sea, and into the subsurface, showing that life had diversified into, and flourished within, a range of different environments early in Earth history.
An important additional component in the search for life on Mars involves the manner in which evidence for early life is preserved. From the examples studied here, early mineralization of organic matter is key to the preservation of reliable biosignatures, in either silica, carbonate, or pyrite, but burial by volcanic ash can also provide excellent preservation.