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Gypsum-hosted endolithic communities of the Lake St. Martin impact structure, Manitoba, Canada: spectroscopic detectability and implications for Mars

Published online by Cambridge University Press:  18 September 2014

T. Rhind ,
J. Ronholm ,
B. Berg ,
P. Mann ,
D. Applin ,
J. Stromberg ,
R. Sharma ,
L.G. Whyte  and
E.A. Cloutis
T. Rhind
Affiliation:
Department of Geography, University of Winnipeg, Winnipeg, Manitoba R3B 2E9, Canada
J. Ronholm
Affiliation:
Department of Natural Resource Sciences, McGill University, Sainte-Anne-de-Bellevue, Quebec H9X 3V9, Canada
B. Berg
Affiliation:
Department of Geography, University of Winnipeg, Winnipeg, Manitoba R3B 2E9, Canada
P. Mann
Affiliation:
Department of Geography, University of Winnipeg, Winnipeg, Manitoba R3B 2E9, Canada
D. Applin
Affiliation:
Department of Geography, University of Winnipeg, Winnipeg, Manitoba R3B 2E9, Canada
J. Stromberg
Affiliation:
Department of Earth Sciences, Centre for Planetary Science and Exploration, University of Western Ontario, London, Ontario N6A 5B7, Canada
R. Sharma
Affiliation:
Department of Geography, University of Winnipeg, Winnipeg, Manitoba R3B 2E9, Canada
L.G. Whyte
Affiliation:
Department of Natural Resource Sciences, McGill University, Sainte-Anne-de-Bellevue, Quebec H9X 3V9, Canada
E.A. Cloutis*
Affiliation:
Department of Geography, University of Winnipeg, Winnipeg, Manitoba R3B 2E9, Canada
*
e-mail: e.cloutis@uwinnipeg.ca
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Abstract

There is increasing evidence that Mars may have once been a habitable environment. Gypsum is targeted in the search for Martian biosignatures because it can host extensive cryptoendolithic communities in extreme terrestrial environments and is widespread on Mars. In this study the viability of using different spectroscopy-based techniques to identify the presence of gypsum endolithic communities was investigated by analysing various cryptoendoliths collected from the Lake St. Martin impact crater (LSM), a Mars analogue site found in Manitoba, Canada. Concurrently, the cryptoendolithic microbial community structure present was also analysed to aid in assigning spectroscopic features to microbial community members. Two main morphologies of endolithic communities were collected from gypsum deposits at LSM: true cryptoendolithic communities and annular deposits on partially buried boulders and cobbles <1 cm below the soil surface. Endolithic communities were found to be visibly present only in gypsum with a high degree of translucency and could occur as deep as 3 cm below the exterior surface. The bacterial community was dominated by a phylum (Chloroflexi) that has not been previously observed in gypsum endoliths. The exterior surfaces of gypsum boulders and cobbles are devoid of spectroscopic features attributable to organic molecules and detectable by reflectance, Raman, or ultraviolet-induced fluorescence spectroscopies. However, exposed interior surfaces show unique endolithic signatures detectable by each spectroscopic technique. This indicates that cryptoendolithic communities can be detected via spectroscopy-based techniques, provided they are either partially or fully exposed and enough photon–target interactions occur to enable detection.

Keywords

biosignaturecryptoendolithgypsumMarsRamanspectroscopy

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Type
Research Article
Information
International Journal of Astrobiology , Volume 13 , Issue 4 , October 2014 , pp. 366 - 377
Copyright
Copyright © Cambridge University Press 2014 

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