The European Space Agency's ExoMars 2020 mission gives the astrobiology community the opportunity to scrutinise instrumentation, landing sites and proposed biosignatures in preparation for this mission. A miniaturised Raman spectrometer will be included as part of the payload instrumentation. The main focus of this work is to test the capabilities of this technique in support of this mission. The impact crater environment is one of the most valuable targets in search for life on Mars. One of the most well preserved craters on earth has evidence of microbial life in the post-impact hydrothermal deposits and the surface mineral crusts. Raman spectroscopy is able to identify more habitable forms of sulphate and detect photo-protective microbial pigments in the crusts. One of the building blocks of life is organic carbon. Raman spectroscopy will primarily be used to characterise organics, and as Mars has a limited atmosphere and lacks a global magnetic field, the surface of Mars is heavily oxidised. The effect that oxidation has on the Raman carbon signal is therefore important. Results show that hematite has an interfering band at the same frequency as the carbon D band, which could result in a misinterpretation of the carbon order, so caution must be taken. Oxidised iron could be a viable energy source of iron-reducing bacteria. One of the most common reduction morphologies in the geological record is the reduction spheroid. They are most likely formed by iron-reducing bacteria, and could be used as a biosignature on Mars. Results show that Raman spectroscopy is able to detect reduction spheroids by tracking the presence of hematite. Experimental work aiming to simulate the formation of a reduction spheroid was unsuccessful but shed light on the complexity of crystalline Fe(III) reduction. This work has highlighted the capabilities and limitations of Raman spectroscopy prior to the ExoMars mission.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:731636 |
| Date | January 2017 |
| Creators | Brolly, Connor |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=235435 |
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