Stephen A. Bowden

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The disappearance of iron formations from the geological record approximately 1.8 billion years (Gyr) ago was the consequence of rising oxygen levels in the atmosphere starting 2.45-2.32 Gyr ago. It marks the end of a 2.5-Gyr period dominated by anoxic and iron-rich deep oceans. However, despite rising oxygen levels and a concomitant increase in marine(More)
Geochemical data from ancient sedimentary successions provide evidence for the progressive evolution of Earth's atmosphere and oceans. Key stages in increasing oxygenation are postulated for the Palaeoproterozoic era (∼2.3 billion years ago, Gyr ago) and the late Proterozoic eon (about 0.8 Gyr ago), with the latter implicated in the subsequent metazoan(More)
The European Space Agency's ExoMars mission will seek evidence of organic compounds of biological and non-biological origin at the martian surface. One of the instruments in the Pasteur payload may be a Life Marker Chip that utilizes an immunoassay approach to detect specific organic molecules or classes of molecules. Therefore, it is necessary to define(More)
Microbial life inhabits deeply buried marine sediments, but the extent of this vast ecosystem remains poorly constrained. Here we provide evidence for the existence of microbial communities in ~40° to 60°C sediment associated with lignite coal beds at ~1.5 to 2.5 km below the seafloor in the Pacific Ocean off Japan. Microbial methanogenesis was indicated by(More)
The survival of organic molecules in shock impact events has been investigated in the laboratory. A frozen mixture of anthracene and stearic acid, solvated in dimethylsulfoxide (DMSO), was fired in a two-stage light gas gun at speeds of ~2 and ~4 km s(-1) at targets that included water ice, water, and sand. This involved shock pressures in the range of 2-12(More)
Soluble and insoluble fractions of the Jet Rock sedimentary organic matter have been subjected to hydropyrolysis to evaluate their biomarker content. Hydropyrolysis is the temperature-programmed pyrolysis of organic matter in an open system fixed bed reactor under high hydrogen pressure in the presence of a sulfided molybdenum catalyst. The hydrocarbon(More)
A simple surface-enhanced Raman spectroscopy (SERS) microflow cell was developed to investigate distributions of scytonemin pigment within cyanobacteria from samples of rock collected from an arctic desert that contained endolithic cyanobacteria. The assay, which has future potential use in a variety of applications, including astrobiology and analysis of(More)
Allwood, A.C., Walter, M.R., Kamber, B.S., Marshall, C.P., Burch, I.W., 2006a. Stromatolite reef from the Early Archaean era of Australia. Nature 441, 714–718. Allwood, A.C., Walter, M.R., Marshall, C.P., 2006b. Raman spectroscopy reveals thermal palaeoenvironments of c.3.5 billionyear-old organic matter. Vib. Spectrosc. 41, 190–197. Awramik, S.M., Schopf,(More)
Introduction: The presence of sulfates on the surface of Mars was indicated by a strong Mg-S correlation in the fluorescence data obtained by the Viking landers [1]. Sulfates were subsequently identified as being present in the soil at the Pathfinder landing site at a concentration of ~ 10 % MgSO4 [2]. Data from the Opportunity rover indicates that sulfates(More)
A catalytic hydropyrolysis procedure was developed for rapidly assessing the relative abundances and variety of different biomarker lipid structures in microbial cultures by reductively converting free functionalised and polymeric lipids within whole cells into hydrocarbons. High pressure hydrogen gas and a molybdenum catalyst were used to target and cleave(More)