| This proposal recognises that determining the nature of the earliest life forms on Earth and potentially Mars, and the geological environment in which life developed, is one of the fundamental goals in science. Finding unambiguous evidence of fossilised early life forms on Earth, based on morphology or fossilised organic molecules, is, however, unlikely due to impact and plate tectonic processes. Equally on Mars, acidic and oxidising conditions, coupled with a high UV flux, mean that organic molecules are unlikely to be preserved. We propose to develop an approach to evaluate the presence of a biosphere on Mars through an integrated mineralogical, chemical and stable isotope method calibrated in terrestrial ecosystems. Three Martian field analogues, highly acidic and/or saline, are chosen for detailed study (Rio Tinto, Spain; Moroccan desert and Tunisian saline lake). A multi-discipline and state-of-the-art analytical study (micro-biology, C-N-S-Si-Fe isotope, in situ mineral and trace element) will rigorously characterise the bio-geochemical and bio-mineralogical response to the presence of life. In particular, the spatial relationships between bio-minerals and the magnitude of stable isotopic fractionations will be constrained in order to develop sampling strategies that can be applied to searches for life on Mars and in terrestrial Archaean rocks. As a final stage of the project, samples from early Archaean environments will be studied to establish if the multi-technique approach is valid and that chemical-isotopic characteristics can be used to assess the nature of the energy sources employed by early terrestrial organisms. |
