Geochemical constraints on the Hadean environment from mineral fingerprints of prokaryotes

• Grant number: 17/12370-8
• Support Opportunities: Regular Research Grants - Publications - Scientific article
• Start date: August 01, 2017
• End date: January 31, 2018
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Carlos Roberto de Souza Filho
• Grantee: Carlos Roberto de Souza Filho
• Host Institution: Instituto de Geociências (IG). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

The environmental conditions on the Earth before 4 billion years ago are highly uncertain, largely because of the lack of a substantial rock record from thisperiod. During this time interval, known as the Hadean, the young planet transformed from an uninhabited world to the one capable of supporting, andinhabited by the first living cells. These cells formed in a fluid environment they could not at first control, with homeostatic mechanisms developing only later. Itis therefore possible that present­day organisms retain some record of the primordial fluid in which the first cells formed. Here we present new data on theelemental compositions and mineral fingerprints of both Bacteria and Archaea, using these data to constrain the environment in which life formed. The cradlesolution that produced this elemental signature was saturated in barite, sphene, chalcedony, apatite, and clay minerals. The presence of these minerals, as well asother chemical features, suggests that the cradle environment of life may have been a weathering fluid interacting with dry­land silicate rocks. The specificmineral assemblage provides evidence for a moderate Hadean climate with dry and wet seasons and a lower atmospheric abundance of CO than is presenttoday. (AU)