Critical testing of Earth's oldest putative fossil assemblage from the ∼3.5Ga Apex chert, Chinaman Creek, Western Australia

A fresh look at the fossil evidence for early Archaean cellular life

“…An abiogenic source for some of this deep Archaean carbon is suggested by the ubiquity of light carbon in deep hydrothermal dyke cherts and by close association with hydrothermal carbonates, sulphates and metals (Nijman et al 1998;Brasier et al 2002Brasier et al , 2005Lindsay et al 2005). This scenario, that there was deep, abundant, hydrothermally generated abiogenic carbon like that found around some modern black smokers, urgently needs to be further tested, not least for its implications to the origins of life.…”

“…It requires us to approach the early Earth as we would a distant planet such as Mars and to take a calm, cautious, multidimensional and multidisciplinary approach to the evidence (e.g. Brasier et al 2005;Westall 2005). …”

Facula, Faculae

“…For example, a combination of infrared spectroscopy (providing an aliphaticity index of the organic matter) and microscale measurements of the carbon isotopic compositions was used by Sangely et al (2007) to distinguish between biology and Fischer-Tropsch-type reactions as genetic processes for the bitumen found in the Cretaceous uranium deposits of Athabasca. Known abiotic products that can mimic life morphologies or chemistries include vesicles made in the laboratory from meteoritic kerogen or in other prebiotic chemistry experiments (e.g., Deamer et al 2006), fluid inclusions, carbonaceous filamentous shapes resulting from migrating organic matter (with carbon isotopic fractionation resembling life patterns) around minerals casts in hydrothermal environments (Brasier 2005;Brasier et al 2006), aggregates of silica spheres and rods in silica-rich waters of hydrothermal springs, migration of carbonaceous materials along microfractures (VanZuilen et al 2007), within or around silica (e.g., Jones and Renaut 2007;Lepot et al 2009b). Finally, mineralized pseudo-fossils have been produced using a mixture of barium carbonate and silica in laboratory experiments (Garcia-Ruiz et al 2003).…”

Nanosims Opens a New Window for Deciphering Organic Matter in Terrestrial and Extraterrestrial Samples

“…Recognition of the earliest morphological or chemical evidence of terrestrial life has proved to be challenging, as organic matter in ancient rocks is commonly fragmentary and difficult to distinguish from abiotically-produced materials (Schopf, 1993;Van Zuilen et al, 2002;Altermann & Kazmierczak, 2003;Cady et al, 2003;Brasier et al, 2002Brasier et al, , 2004Brasier et al, , 2005Hofmann, 2004;Skrzypczak et al, 2004Skrzypczak et al, , 2005). Yet, the ability to identify remnants of earliest life is critical to our understanding of the timing of life's origin on earth, the nature of earliest terrestrial life, and recognition of potential remnants of microbial life that might occur in extraterrestrial materials.…”

“…Thus, recent efforts have been directed toward finding biosignatures that can help distinguish fragmentary remnants of ancient microbes from either pseudofossils or abiotic organic materials that may have formed hydrothermally or in extraterrestrial processes (House et al, 2000;Boyce et al, 2001;Kudryavtsev et al, 2001;Schopf, 2002;Schopf et al, 2002Schopf et al, , 2005aCady et al, 2003;García-Ruiz et al, 2003;Hofmann, 2004;Brasier et al, 2005;Rushdi and Simoneit, 2005;Skrzypczak et al, 2005).…”