A recent study conducted by the University of Ottawa, Carleton University, and University College London challenges the long-held belief that the isotopic composition of carbon in iron formations from the Saglek-Hebron Complex in Nunatsiavut provides evidence of the earliest traces of life on Earth. The research suggests that the petrographic, geochemical, and spectroscopic features in the graphite found in the rocks are abiotic in nature, meaning they are nonliving physical or chemical aspects devoid of life. This new perspective enhances our understanding of how early biomass transformed on Earth and highlights the interaction between non-biological processes and ancient life remnants.
Decoding carbon cycling on the early Earth is crucial for understanding the evolution of life on our planet. The study, titled “Abiotic synthesis of graphitic carbons in the Eoarchean Saglek-Hebron metasedimentary rocks,” published in Nature Communications, sheds light on the formation of graphitic carbons in ancient rocks. Analyzing graphitic materials is essential for unraveling the mysteries of the past and exploring the potential existence of ancient life on Earth and other planets.
The researchers revisited the isotopic signatures in the rocks from the Saglek-Hebron Complex to reevaluate the origin of the graphitic carbon. Contrary to previous assumptions, the study found that the graphite in the rocks may have originated from liquid substances containing carbon, hydrogen, and oxygen, possibly derived from the breakdown of old organic materials. This challenges the idea that the carbon isotopic composition of these ancient rocks indicates a biological origin and suggests a more abiotic nature.
Samples collected in Nunatsiavut during a field campaign in 2016 were analyzed through petrological characterization in Ottawa and spectroscopic analysis of graphitic carbon in London. The results showed that the graphitic carbon in the nearly 3.9 billion-year-old sedimentary rocks was likely formed from metamorphic fluids at high temperatures, rather than through bacterial processes. The degree of crystallization of the graphite was found to correlate with the rocks’ metamorphism, indicating the impact of metamorphic processes on the preservation and alteration of carbon-based materials.
The study challenges the conventional wisdom surrounding the origin of graphitic carbon in ancient rocks, prompting a reassessment of the processes responsible for isotopic signatures and their potential connection to microbial activity. By exploring the possibility of abiotic synthesis of graphitic carbons, researchers are broadening our knowledge of early Earth processes and paving the way for new discoveries in the search for ancient life forms. The findings from this study may have far-reaching implications for our understanding of the origins of life on Earth and beyond.
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