Graphitic carbons and biosignatures

Abstract

The unambiguous identifi cation of graphitic carbons as remains of life in ancient rocks is challenging because fossilized biogenic molecules are inevitably altered and degraded during diagenesis and metamorphism of the host rocks. Yet, recent studies have highlighted the possible preservation of biosignatures carried by some of the oldest graphitic carbons. Laboratory simulations are increasingly being used to better constrain the transformations of organic molecules into graphitic carbons induced by sedimentation and burial processes. These recent research advances justify a reevaluation of the putative biogenicity of numerous ancient graphitic carbons, including the presumed oldest traces of life on Earth.