DOMINIC PAPINEAU; HTTPS://ORCID.ORG/0000-0003-0063-7514 ZHENBING SHE; HTTPS://ORCID.ORG/0000-0003-0068-9138MATTHEW S. DODD; HTTPS://ORCID.ORG/0000-0003-4470-933XFRANCESCO IACOVIELLO; HTTPS://ORCID.ORG/0000-0003-3564-2380JOHN F. SLACK; ERIK HAURI; HTTPS://ORCID.ORG/0000-0002-7449-4774PAUL SHEARING AND CRISPIN T. S. LITTLE
SCIENCE ADVANCES • 13 Apr 2022 • Vol 8, Issue 15 • DOI: 10.1126/sciadv.abm2296
The oldest putative fossils occur as hematite filaments and tubes in jasper-carbonate banded iron formations from the 4280- to 3750-Ma Nuvvuagittuq Supracrustal Belt, Québec. If biological in origin, these filaments might have affinities with modern descendants; however, if abiotic, they could indicate complex prebiotic forms on early Earth. Here, we report images of centimeter-size, autochthonous hematite filaments that are pectinate-branching, parallel-aligned, undulated, and containing Fe2+-oxides. These microstructures are considered microfossils because of their mineral associations and resemblance to younger microfossils, modern Fe-bacteria from hydrothermal environments, and the experimental products of heated Fe-oxidizing bacteria. Additional clusters of irregular hematite ellipsoids could reflect abiotic processes of silicification, producing similar structures and thus yielding an uncertain origin. Millimeter-sized chalcopyrite grains within the jasper-carbonate rocks have 34S- and 33S-enrichments consistent with microbial S-disproportionation and an O2-poor atmosphere. Collectively, the observations suggest a diverse microbial ecosystem on the primordial Earth that may be common on other planetary bodies, including Mars.
