title: Raman spectroscopic analysis of minerals and organic molecules of relevance to astrobiology.
abstract: Characteristic geological features and hydrated minerals recently found on the surface of Mars by the NASA planetary rovers Spirit and Opportunity suggest that a possible biosphere could have once existed there. Analytical instrumentation protocols for the unequivocal detection of biomarkers in suitable geological matrices are critical for future unmanned explorations, including the forthcoming ESA-ExoMars mission scheduled for 2018. Raman spectroscopy is currently a part of the Pasteur instrumentation suite of the ExoMars mission scheduled for 2018 for the remote detection of extant or extinct life signatures in the Martian surface and subsurface. Terrestrial analogues of Martian sites have been identified, and the biogeological modifications incurred as a result of extremophilic survival activity have been studied. Polyaromatic hydrocarbons (PAHs) are recognised as a class of degradation product that occur from biological processes terrestrially. In this work, various concentrations of polyaromatic hydrocarbons in matrices of gypsum, calcite and quartz have been investigated by Raman microspectrometry to determine the lowest detectable organic levels. The studies are conceived in simulation of their potential PAHs identification in geobiological conditions in Martian scenarios. Two laser source wavelengths, namely, 785 and 633 nm, were adopted to excite Raman spectra from the PAHs, which represent degraded carbons and therefore potentially provide a key bimolecular marker of ancient life.
authors.affiliation: Centre for Astrobiology & Extremophiles Research, School of Life Sciences, University of Bradford, Bradford, West Yorkshire, BD7 1DP, UK.
authors.forename: A I
authors.initials: AI
authors.lastname: Alajtal
authors.affiliation: Centre for Astrobiology & Extremophiles Research, School of Life Sciences, University of Bradford, Bradford, West Yorkshire, BD7 1DP, UK. h.g.m.edwards@bradford.ac.uk.|University Analytical Centre, University of Bradford, Bradford, West Yorkshire, BD7 1DP, UK. h.g.m.edwards@bradford.ac.uk.
authors.forename: H G M
authors.initials: HGM
authors.lastname: Edwards
authors.affiliation: Centre for Astrobiology & Extremophiles Research, School of Life Sciences, University of Bradford, Bradford, West Yorkshire, BD7 1DP, UK.|University Analytical Centre, University of Bradford, Bradford, West Yorkshire, BD7 1DP, UK.
authors.forename: I J
authors.initials: IJ
authors.lastname: Scowen
mesh_terms: D015415:Biomarkers / Q000032:analysis; D002119:Calcium Carbonate / Q000737:chemistry*; D002133:Calcium Sulfate / Q000737:chemistry*; D018559:Exobiology; D008903:Minerals / Q000032:analysis*; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis*; D011791:Quartz / Q000737:chemistry*; D013026:Space Flight; D018561:Space Simulation; D013059:Spectrum Analysis, Raman
chemical_list: D015415:Biomarkers; D008903:Minerals; D011084:Polycyclic Aromatic Hydrocarbons; D011791:Quartz; D002119:Calcium Carbonate; D002133:Calcium Sulfate