Identificationand characterization of the first cells (and/or of traces of life)

Although it is admitted that life existed in the Early Archean, the reliable recognition of cells and their metabolism to date the transition of the prebiotic world to the live world is at stake. To unlock this technology, we (L. Lemelle and coll.) plan to develop the nano-imaging of metals in microfossils (oriented on criteria of shape by optical microscopy in Archaean rocks of South Africa), thanks to the emergent technology of synchrotron hard X-rays nano-beams (ESRF of Grenoble; Figure). This non-invasive and non-destructive technique allows observing a microstructure at the nm scale.

In parallel, we also establish experimental and numerical models of the biogeochemical impact of the interactions between bacteria and reactive surfaces. This work is important to recognize possible forms/traces of life on the Primitive Earth, but also onother planets.

We also focus our research on field studies and micropaleontological prospection of sedimentary series ranging in age from 1.8 to 2.5 Ga, and potentially bearing the earliest eucaryote microfossil record (F. Cordey). Our strategy is based on analyzing fine-grained sequences with low rates of sedimentation such as hemipelagic environments, more favourable to cell fossilization than high-energy coastal sequences usually sampled by paleobiologists. Our exploration presently targets several Paleoproterozoic units from Canada and western Australia.

Participants : Laurence Lemelle (CR), Fabrice Cordey (Pr), Gilles Dromart (Pr), Eléonore Mottin (Tech)