HYPERSALINE ACID LAKES IN SOUTHWESTERN AUSTRALIA AS DEPOSITIONAL AND EARLY DIAGENETIC ANALOGS FOR THE BURNS FORMATION ON MARS

The mineralogy and sedimentology of acid saline lakes in the Yilgarn Block of southwestern Australia provide a rare modern analog for ancient acidic hypersaline deposits in the geologic record both on Earth and on Mars. Acid saline systems on both planets contain primary and secondary sulfates, as well as secondary jarosite and iron oxides, including hematite, in the form of spheroidal concretions. The recent images and geochemical data acquired by NASA's Mars Exploration Rovers reveal a unique suite of minerals and sedimentary structures within the Burns Formation that are consistent with deposition in and around an acid saline lacustrine environment. Similar features are seen in the ancient Earth record within the Permian Nippewalla and Opeche rocks of the U.S. midcontinent. The modern Australian lakes, groundwaters, and sediments have extreme and dynamic geochemical conditions. For example, pHs among lakes range from 2.5 to 8.2 and total dissolved solids reach up to 270 parts per thousand. Preliminary investigations suggest microbial life is present even in these extreme conditions. Evaluation of preservation potential for life within these environments can help to provide guidelines for how the search for life on Mars might continue.