Montreal Space Symposium

Space agencies and private corporations around the world have made sending missions to Mars a key priority. One of the keys to such missions is finding an environment which would allow for ease of access while providing a compelling site to do science. Scientists have hypothesized that evidence for life on Mars, either as biosignatures (substance providing evidence for life) or extant life could be found in the Martian subsurface. This would be made possible by providing would-be Martian microbes a source of water in the form of ice, ample protection both from space-based radiation, and harsh temperature changes. Martian lava tubes are hypothesized to provide these protections while additionally providing an access point to the subsurface. To determine suitable landing sites for a mission to a Martian lava tube, imagery from the Hi-RISE database, provided by the University of Arizona was analysed. Regions selected for study included Tharsis Montes and Syrtis Major due to their hypothesized high density of lava tubes. Analysis of the images confirmed this hypothesis, as we found several sites with a high concentration of sinuous formations, which are usually indicative of these structures. Using this imagery, the presence of lava tubes and identification of entry-points to the subterranean structures was confirmed with the help of experts in Martian geology. Final selection of the landing site was determined by addressing engineering constraints surrounding spacecraft delivery. From these criteria, several possible sites were selected, ranging in location from Olympus Mons to Syrtis Major. However, before a mission to Martian lava tubes can occur these habitats need to be studied extensively in analog environments here on earth; to suggest how microbes could survive on Mars and identify biosignatures. For this we visited Lava Beds National Monument to collect ice samples from within the lava tubes. Advanced cultivation and molecular techniques were employed to determine the total biomass and functional/taxonomic diversity of the microbial communities. The microbial communities within the ice are cold adapted and taxonomically diverse with dominant phyla belonging to Actinobacteria (19 – 49%), Proteobacteria (25 – 32%), and Bacteroidetes (7 – 31%). Preliminary results have identified biochemical pathways within our samples for methanogenesis, sulfur metabolism, nitrogen fixation, and carbon fixation by the reductive citric acid pathway which suggest the community is made up in part by chemolithoautotrophs. Alternative forms of primary production such as these may help to sustain the community in such a limiting environment and are no doubt essential if life were to persist on Mars today where the concentration of organic nutrients is low. Through this research we hope to define future missions to Martian lava tubes and provide a basic understanding of microbial community dynamics within lava tube ice and how these communities interact with the surrounding geology, so we may better determine the habitability of this environment on Mars and propose biosignatures indicative of past life.