Interpretation of biosignatures in extreme environments, and their potential impact for the search for life on Mars

• Main Author: Nauny, Philippe É. M.
• Format: Thesis
• Language: English
• Published: 2019
• Subjects: QD Chemistry; QE Geology; QH Natural history; Iceland
• Online Access: https://theses.gla.ac.uk/77875/; https://theses.gla.ac.uk/77875/1/2019NaunyPhD.pdf; https://doi.org/10.5525/gla.thesis.77875

The search for life beyond Earth, and on Mars in particular, is one of the key points of astrobiology research. However, space missions are expensive and time-consuming. Simulating such missions at analogue sites on Earth can thus save time and money whilst working in natural settings. This thesis presents three studies of biosignatures from three different martian analogues. These biosignatures were linked — when possible — to environmental parameters observed at their sampling sites. The first study was set in a hot a dry environment in the Atacama Desert in Chile. It aimed to identify biolipids and genetic material in soil samples, along a high-resolution shallow depth profile in a dry alluvial fan. Signs of microbial life were observed at the surface, despite the extreme environmental conditions, and at deeper depths — together with degraded plant material — above a layer of very fine grained sands and silts. Overall, biolipids of plant origin showed the strongest concentrations, despite the quasi-absence of plants at the surface. The poor quality of the DNA sequencing results prevented their interpretation. The sedimentation history of the sampling site seemed to be more complex than what could be observed at the surface. The second study was on the flank of the Sairecabur, a high-altitude volcano in Chile. Soil samples, taken along four depth profiles following an altitude gradient, were analysed for their biolipids and genetic material content. Again, biolipids of plant origin showed the strongest concentrations — both at vegetated and barren sites — and the poor quality of the DNA sequencing results prevented their interpretation. Additionally, the variable environmental and physico-chemical conditions at the different sampling sites makes it more challenging to draw conclusions regarding the altitude gradient. The third study took place inside the crater of Hverfjall, a tuff ring volcano in Iceland. Colonisation of the crater by life was studied by measuring microbial activity and biolipids in soil ...