Roger E. Summons, Ph.D.

SCOL Project: The Geological Record of Early Life on Earth

The proposed research addresses four aspects of the geological record of early life on Earth. Firstly, we will explore Earth’s oxygenation history and the impact of oxygenation on the interconnections between the biogeochemical cycles of carbon, sulfur and nitrogen. We explore this topic using the stable isotopic patterns of C and N in organic matter and S preserved as pyrite in sediments recovered from new drill cores from the ancient terranes of South Africa and Western Australia.

An enduring problem encountered in early life records is establishing whether or not organic matter and other putative fossils are really the remains of organisms or pseudofossils formed by some non-biological process. Our plan for evaluating biogenicity of Archean organic matter will use advanced tools, including scanning transmission X-ray microscopy and micro-Raman spectroscopy, to examine the mineralogical contexts and spatial relationships of preserved carbonaceous remains. We will also conduct laboratory experiments to study preservation mechanisms in contrasting chemical environments.

Considerable controversy surrounds the early record of chemical fossils. In probing the Proterozoic molecular fossil record we will investigate the preservation of the hydrocarbon remains of membrane lipids preserved in rocks as old as 1.65 billion years using new methods to assess the authenticity of these compounds. We will particularly study all forms of evidence that might allow us to identify the main primary producers in the early oceans.

To complement our studies of ancient membrane lipids preserved in rocks we will collaborate with other SCOL investigators (e.g., Welander, Fournier and Sutherland) to investigate the origin of complex lipid membranes through structural characterization of archaeal and bacterial lipids, as well as genomic studies of lipid biosynthesis pathways leading to phylogenetic and molecular clock analyses. In this work we hope to learn more about when where these key pathways first arose.

Bio:
Roger Summons is Schlumberger Professor of Geobiology in the Department of Earth, Atmospheric and Planetary Sciences at the Massachusetts Institute of Technology. Prior to taking up that appointment in 2001, he was at Geoscience Australia in Canberra. Over a period of 18 years at Geoscience Australia (formerly BMR and then AGSO) he was a member, then leader, of a research team studying the distinctive nature and habitat of Australian petroleum and the evolution of the biogeochemical carbon cycle.

At MIT his research group studies the co-evolution of Earth’s early life and environment, biosignatures of microbially-dominated ecosystems, the structures and biosynthetic pathways of membrane lipids, biological mass extinction events and the origins of fossil fuels. Summons, originally trained as an organic chemist, was awarded B.Sc. (1969) and Ph.D. (1972) degrees in chemistry from the University of New South Wales’ Wollongong College (now the University of Wollongong). He undertook postdoctoral research in the Genetics Department at Stanford University and in the Research Schools of Chemistry and Biological Sciences at the Australian National University, Canberra. He was elected fellow of the Australian Academy of Science in 1998, the American Geophysical Union in 2006, the Royal Society in 2008 and the American Academy of Microbiology in 2012 and is author or co-author of more than 350 research papers in organic chemistry, geochemistry, geomicrobiology and astrobiology. Summons was a participating scientist on the Mars Science Laboratory mission and pursues his interest in Earth’s early life as a SCOL Investigator.