X-ray Spectroscopy and Electron Microscopy of Martian Meteorites and UV-IR Spectroscopy of Martian Brine Analogues

This thesis focuses on the mineralogical study of altered martian meteorites and the development of a novel wet-chemistry instrument. X-ray spectroscopy and electron microscopy have been used to investigate the secondary mineralogy of martian meteorites and their associated fluids. Martian analogue brines were investigated with transmission spectroscopy in order to address the technique’s capabilities for detecting dilute, astrobiologically significant fluids.

The newly-found martian shergottite, Northwest Africa (NWA) 10416, bears a distinctive colouration in its olivine megacrysts which is suggestive of hydrous alteration. The meteorite has been petrographically characterised and the origin of its alteration has been determined as terrestrial. Oxygen isotope analysis and the observation of secondary phases within shock features using Transmission Electron Microscopy (TEM) have indicated a terrestrial fluid. Synchrotron X-ray Absorption Spectroscopy (XAS), X-ray Diffraction (XRD) and Electron Probe Micro-Analysis (EPMA) have allowed its characterisation as a low-temperature, possibly acidic, fluid.

Analysis of the martian nakhlite, Lafayette, has been performed in order to assess the extent of carbonate dissolution by a hydrothermal martian fluid. Textures determined by Scanning Electron Microscopy (SEM) and TEM, and compositions determined by EPMA and XAS have displayed the variable nature of this dissolution and allowed the identification of the mesostasis phyllosilicate as odinite. This work has illustrated a process in which martian crustal fluids can dissolve carbonates and produce substantial amounts of methane, informing our understanding of martian atmospheric methane.

The capabilities of transmission spectroscopy when detecting organic martian analogue brines have been assessed to further the development of the wet-chemistry instrument, ASPIRE. Transmission spectroscopy was unsuccessful in detecting the likely low organic concentrations (ppb) expected in potentially habitable martian aqueous environments. However, future avenues of research have been suggested for consideration, including investigation into the potential of reflectance spectroscopy and calibration of ASPIRE to mineralogical-free regions within the infrared region.