Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Planetary Science

Supervisor

Dr. Gordon Osinski

2nd Supervisor

Dr. Neil Banerjee

Joint Supervisor

Abstract

The initial catastrophic biological effects of hypervelocity impacts are well established. However, a growing body of evidence suggests that meteorite impact events have beneficial effects for microbial life. This, in turn, has led many to suggest that impact craters may have been important habitats for life on early Earth. Any large meteorite impact into a water-rich target on a solid planetary body has the potential to generate hydrothermal systems. Impact-generated hydrothermal systems expand the potential environments for microbial colonization to environments without endogenous volcanic heat sources to drive hydrothermal activity. Examination of impact glass from the Ries impact structure, Germany, has revealed the presence of putative microbial alteration. Given the probable ubiquity of impact glasses in post-impact environments throughout the Solar System, it is important to understand the biological components and potential of such systems. A multi-analytical approach to assess the biogenicity of the tubular features in the Ries glasses has been used. Their complex morphology (spiralling, bifurcation, avoidance, lack of intersection) has been studied extensively using both optical and scanning electron microscopy. Using Energy Dispersive Spectroscopy we have shown the presence of a depletion zone indicative of biological processing surrounding the tubules. Fourier Transform Infrared Spectroscopy has identified the presence of organic compounds spatially associated with the tubules and absent in crystallite regions. Synchrotron near edge fine structure (NEXAFS) spectroscopy at the C K-edge also indicates the presence of organically bound carbon in the glassy matrix surrounding the tubules, but absent in the matrix hosting only crystallites. NEXAFS spectroscopy at the Fe L2 and L3 -edges indicates distinct patterns of Fe speciation in the tubules not present in the Fe-rich abiotic quench crystallites. Together, these results are strongly suggestive of a microbial alteration origin for the tubules in the Ries glasses. Impact cratering is a significant and ubiquitous geological process on terrestrial bodies in the Solar System as well as on the early Earth, as such the discovery of biogenic features in impact glass has profound implications for early life on Earth and the early evolution of life on Earth as well as for life on other terrestrial planets.

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