Journal
ASTROBIOLOGY
Volume -, Issue -, Pages -Publisher
MARY ANN LIEBERT, INC
DOI: 10.1089/ast.2019.2144
Keywords
Isotope biosignature; Early life; Archean; Carbon isotope; Nitrogen isotope
Funding
- Programme National de Planetologie (PNP) of the CNRS INSU
- EU's Horizon H2020 research and innovation program ERC (STROMATA) [759289]
- CNES
- European Research Council (ERC) [759289] Funding Source: European Research Council (ERC)
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Stable isotope signatures of elements related to life such as carbon and nitrogen can be powerful biomarkers that provide key information on the biological origin of organic remains and their paleoenvironments. Marked advances have been achieved in the last decade in our understanding of the coupled evolution of biological carbon and nitrogen cycling and the chemical evolution of the early Earth thanks, in part, to isotopic signatures preserved in fossilized microbial mats and organic matter of marine origin. However, the geologic record of the early continental biosphere, as well as its evolution and biosignatures, is still poorly constrained. Following a recent report of direct fossil evidence of life on land at 3.22 Ga, we compare here the carbon and nitrogen isotopic signals of this continental Archean biosphere with biosignatures of cyanobacteria biological soil crusts (cyanoBSCs) colonizing modern arid environments. We report the first extended delta C-13 and delta N-15 data set from modern cyanoBSCs and show that these modern communities harbor specific isotopic biosignatures that compare well with continental Archean organic remains. We therefore suggest that cyanoBSCs are likely relevant analogues for the earliest continental ecosystems. As such, they can provide key information on the timing, extent, and possibly mechanism of colonization of the early Earth's emergent landmasses.
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