Searching for stromatolites: The 3.4 Ga Strelley Pool Formation (Pilbara region, Western Australia) as a Mars analogue

Stromatolites are readily identified, outcrop scale indicators of potential biological activity, even though constructed by microbes. Their presence in −J.5 Ga volcano-sedimentary successions of the Pilbara region of Western Australia suggests that they might also occur in similar, Noachian-agc successions On Mars. Field and basic laboratory studies of one such occurrence near Nullagine highlight many issues that would be faced by any stromatolite search strategy on Mars. Firstly, the stromatolites are found in local aggregations that make up a very small part of the overall succession, possibly as little as one millionth of the outcrop area. An effective search strategy would require a combination of remote sensing to highlight features with high probability of hosting stromatolites, precision landing, and extensive cross-country mobility, difficult to achieve with a purely unmanned exploration system. Secondly, the limited analytical suite available to any unmanned mission would make conclusive determination of the biogenicity of any stromatolite-like feature on Mars very difficult. This is shown by the controversy over the biogenicity of the Pilbara examples, despite a much greater range of analytical techniques applied to the Pilbara examples. Once possible stromatolites features have been found on Mars, sample return would be imperative to determine their biogenicity.