Hematite Concretions from Modern Acid Saline Lake Sediments as Geochemical and Astrobiological Tombs

Ubiquitous hematite spherules interpreted as being concretions [1] within reworked evaporite dune and interdune lake sediments [2] in the Meridiani Planum region of Mars have revealed a wealth of information about the role of acid saline waters in the planet's past. The variety of processes and conditions that could generate such deposits raises many questions about the formation of mixed iron oxide and evaporite sediments, the potential role of organisms in presumably hostile acid saline systems, and the preservation potential of organisms within this sedimentary record. Sediments from the shallow acid saline lakes in southern Western Australia (Figure 1) provide an important modern analog environment that illustrates potential early and rapid formation of hematite concretion-bearing evaporites, and the excellent astrobiological preservation potential of such deposits.