A new habitability assessment and organic matter detection instrument for Mars

Mars Sample Return is the next major step in the search for life beyond Earth. Mineralogical studies have revealed a wetter, more dynamic Mars than previously considered; the past environments of Mars could have hosted life and the search for its remains is a major scientific preoccupation. The return to Earth of the very best samples requires an effective prioritization and selection process, thus there is a requirement for a triage instrument which examines mineral phases in situ to determine the habitability potential of a region and to detect important biosignatures contained in any rock. This thesis demonstrates the viability of a pyrolysis-Fourier transform infrared spectroscopy (FTIR) instrument to fulfil these mission requirements. Thermal decomposition techniques have long been used on Mars to analyse solid samples, and FTIR instruments have been successfully deployed on the Martian surface. The combination of the two presents a resource efficient and robust analytical solution. Investigations were conducted using pyrolysis-FTIR to show how habitability and the biosignature preservation potential of rocks can be assessed through the release of key gases, namely carbon dioxide, water and sulfur dioxide. The sensitivity limits for detecting organic matter and the effects of different mineral matrices on the organic compound signal were also investigated though measurement of methane and larger hydrocarbon compounds. Finally a field study was conducted using samples collected from a sulfate stream ecosystem which represents an analogue for the Hesperian of Mars. The investigations have shown that pyrolysis-FTIR, through utilisation of different temperature modes and the qualitative and quantitative feedback of resulting spectra, provides adequate information to determine mineral phases relating to habitability. Pyrolysis-FTIR detects organic compounds present in quantities as low as tens of parts-per-million. Sulphates and chlorinated mineral phases diminish organic compound signals, but combustion products offer another avenue for detection. The field study demonstrated that a phased pyrolysis-FTIR protocol will select the most valuable samples. This thesis includes recommendations for the progress of pyrolysis-FTIR to the next design iteration.Open Acces