Earth’s Earliest Biogeochemical Cycles

e quest to understand the nature, physiological capabilities and habitats of early life on Earth remains a challenging scientific issue, due to a slate of cryptic clues and a paucity of credibly preserved historical records. Using state-of-the art mass spectrometric methods we are interrogating the best available sedimentary records of organic and inorganic carbon, nitrogen and sulfur for isotopic and molecular evidence of biogeochemical cycling of C and S, autotrophic carbon assimilation, and light-harvesting processes. Studies of contemporary natural settings and laboratory experiments provide a framework for the interpretation of ancient rocks.

This research addresses question #10 of the Simons Foundation Origins of Life Collaboration program: What is the earliest record of microbial life? How can geochemistry constrain the timing and environments of the origin and early evolution of life?

From the North Pole Dome of the Pilbara Craton, we are studying organic carbon-containing sediments of the ~3.5-3.3 billion year old Warrawoona and Gorge Creek groups. Here, putative microfossils, stromatolites and isotopic clues have been reported and ascribed to biological processes. Our research addresses the chemical and isotopic characteristics of the organic matter preserved in these sediments.

Collaborators include Abigail Allwood and Ken Williford (JPL), Andrew Knoll (Harvard), Shuhei Ono and Tanja Bosak (MIT) and Tomaso Bontognali (ETH).