Constraining the Timing and Nature of Life's Emergence in Extrema: the Geology and Geochemistry of Akilia Island, West Greenland

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Stephen J. Mojzsis, T. Mark Harrison, Craig E. ManningThe emergence of the first life on Earth can be viewed as having occurred in the context of an extreme environment at the global scale. A detailed program of fieldwork and geochronological studies coupled with stable isotopic (C, N, S) investigations is used to explore the oldest known marine sedimentary rocks, from southern West Greenland, that contain a record of these earliest times. These rocks are between 3.7 and 3.9 billion years old. A two-pronged approach is taken to study the sedimentary record of Earth's earliest extreme environments. First, P. Is.' are revealing the geological context and history of the rocks related to petrogenesis and subsequent protracted metamorphism from field studies, metamorphic petrologic observations, and U-Pb zircon geochronological investigations. Second, their study searches for isotopic tracers in the form of C, N, and S fractionations induced by life and preserved in the oldest sediments. P.Is.' view is that these two approaches together will lead the advance in understanding the extremes of early environments for life on Earth. This research is utilizing new ultra-high resolution mass spectrometric techniques (MC-SIMS, C-GC-IRMS, LEC-SMS) developed by UCLA and project collaborators to make these measurements. With this work, the number of biogeochemical tools will increase in power and diversity for detecting potential evidence for early life and the timing of its appearance, in older rocks from Earth when they are found, and eventually in samples from other worlds, like Mars, and Europa.