Endostromatolites: Life in extreme environments and lessons for the detection of life on Mars

• Main Author: Pellerin, Andre
• Format: Thesis
• Language: English
• Published: University of Ottawa (Canada) 2008
• Subjects: Geology; Paleontology; Arctic; Devon Island; Nunavut; permafrost
• Online Access: http://hdl.handle.net/10393/27603; https://doi.org/10.20381/ruor-18794

Finely laminated carbonate columns---endostromatolites, grow in carbonate rock fissures in permafrost regions. Their formation is thought to be microbially mediated but the processes of accretion are thought to be very slow and possibly intertwined with abiotic mineralization processes. The samples analyzed in this study are from the Haughton impact structure, located on Devon Island, Nunavut in the Canadian high Arctic. The carbon and nitrogen isotopic composition of the endostromatolites, along will the microbial community diversity were determined. The delta13C and delta 15N of the organic matter contained within the endostromatolites averaged around -30‰ and 0‰, respectively. Scanning electron microscopy observations revealed the presence of spheroidal calcite and filamentous structures reminiscent of biological activity. Molecular phylogenetic analysis of the endostromatolites and soil samples found in Haughton crater showed that the endostromatolite microbial community is mostly aerobic and chemoheterotrophic, belonging in large part to the Phylum Actinobacteria and the subphylum Alphaproteobacteria. Rubrobacter radiotolerans was the dominant species in the endostromatolites. Soil bacterial communities were more diverse, harboring all the phyla found in the endostromatolites as well as many others which were not encountered in endostromatolites. Understanding the variability of microbial life between specific environments might shed some light on the mechanisms responsible for endostromatolite formation and provide useful data for contrasting abiotic and biotic systems on earth and other planetary bodies, such as Mars.