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Executive Summary

During the fifth year of funding from the NASA Astrobiology Institute, multiple journal papers were published on microbiological, geochemical, and geophysical work in permafrost and sub-permafrost environments at the Lupin gold mine and the High Lake mining property in Nunavut Territory, Canada. Members of our team and collaborators continue to pursue laboratory investigations on microbiological samples we collected during 2005, 2006 and 2007 in the subsurface of the Canadian Arctic. We are now actively pursuing field and laboratory projects that extend our understanding of the fate of microbes and organic molecules in subsurface and surface settings that serve as analogues for present and past environments on Mars. In the following summary, we highlight progress on five projects.

Microbial survival under simulated Martian conditions

An award from the 2007 Director’s Discretionary Fund is being used to initiate a multi-investigator laboratory simulation of the fate of terrestrial organisms and molecules in regions on Mars with the potential for liquid water at or near the surface during summer. Participating scientists are affiliated with the Indiana, SETI and Ames Astrobiology Teams as well as several universities in the U.S. and Canada. A variety of microorganisms were selected for these simulation experiments on the basis of desiccation resistance and cold tolerance under a low-pressure atmosphere composed primarily of carbon dioxide. These experiments will help to evaluate forward contamination of Mars by landed space craft and will guide the design of canisters for storage of organic and inorganic constituents during future sample caching on the Martian surface.
Numerous microorganisms, including nematode and fungal species, have been screened for long duration experiments in the Mars Environmental Simulation Chamber using low temperature, long term desiccation experiments performed with artificial regolith that was formulated specifically for use in this study. The Indiana Mars regolith is representative of inferred mineralogy and elemental compositions for fine-grained sediment derived from Martian basalts and andesitic basalts. Ferric oxides, magnesium sulfates, phyllosilicates, ferric sulfates and clinoptilolite are added to powdered basalt in proportions that reflect surface minerals detected by the Mars Exploration Rovers, and then sterilized. After this initial testing, the desiccation-resistant strains of one nematode, one fungus, one halophilic Archaeon, one methanogen, and six bacteria were selected for the Mars simulation experiment. Naked deoxyribonucleic acid (DNA) and mixtures of common amino acids will also be added to Indiana Mars regolith and reacted in a Mars environmental chamber at the Techshot engineering company during October and November of 2008. The water content in the Mars chamber will be carefully monitored and methanogenic activity will be documented by measuring methane generation during the course of the experiment.

Formation and preservation of amino acids and peptides in brines

A series of experiments in hypobaric environmental chambers are being used to evaluate diurnal cycling of saline brines at or near the surface of present-day Mars. Brine compositions are dominated by sulfate, magnesium, iron, calcium, sodium, and chloride as inferred for acidic weathering of olivine-bearing basaltic rocks on Mars. Amino acids are added to the brines with an excess of left-handed molecules to simulate the preservation of common molecular biomarkers. Initial results indicate that iron-rich brines exposed to mid-range ultraviolet radiation are prone to increased levels of amino acid degradation inferred to result from photo-oxidation reactions. In the absence of ultraviolet radiation, iron-rich brines provide enhanced amino acid preservation. These intriguing results suggest that preservation of organic matter on Mars could be enhanced during precipitation of fine-grained hematite such as occurred during formation of the blueberry concretions discovered by the Mars Exploration Rovers.

Radiolysis as a source of biosustaining energy

Using biomass samples collected by filtration of groundwater from deep gold mines in the Witwatersrand Basin of South Africa, we have analyzed the first metagenome from a deep subsurface environment. This study reveals the genetic composition of a new genera/species of sulfate reducing bacteria, Desulforudis Audaxviator, which is capable of existing as the sole resident of its isolated subsurface environment. A single species ecosystem has not been reported previously and runs counter to the prevalent concept that microorganisms live and evolve as communities of mixed species. It remains to be determined if this bacterial species occurs in other deep subsurface environments on Earth or if other deep subsurface environments are occupied by other single species.

Sulfur cycling in gypsum dunes and sulfate lakes in the southwestern U.S.

Sulfates are a critical component of rocks and regolith exposed at or near the surface of Mars. We are pursuing, therefore, a latitudinal study of salt basins developed along the Rio Grande rift in North America as a terrestrial analog for sulfate deposition in down-dropped basins and craters on Mars. This project addresses local and regional influences of volcanism on sulfur cycling, biogeochemical roles of organism in sulfate-dominated playa lakes and climatic controls on formation of gypsum dunes. Initial results indicate that sulfate in modern playas, paleo-lakes and gypsum dunes is sourced primarily from underlying Permian evaporates during dissolution by meteoric waters with only minor contributions from oxidation of ascending hydrothermal fluids. Surprisingly, isotopic signatures related to microbial sulfate reduction are not evident in most of the studied lake and dune deposits from the Rio Grande rift. By extension to Mars, it appears that gypsum dunes in the Olympia-Undae region on Mars could be sourced from confined groundwater or surface water episodically released during melting of the Martian polar ice cap.

International collaboration to drill and monitor a sub-ice sheet borehole in Greenland

An international group (Canada, Sweden, Finland, and U.S.) of collaborating scientists participated in a field campaign in southwestern Greenland to seek suitable sites for drilling a one-kilometer-long bore hole to enable monitoring of hydrologic conditions and microbial communities beneath an active ice sheet. Fieldwork was conducted along the margins of glaciers (Figure X) that reach the coast near the town of Kangerlussuaq. Metamorphic rock types and fabrics (foliation, shear zones, faults, and joints/fractures) were described and mapped in outcrops along the margins of the ice. Particular attention was given to open versus closed fracture networks and to the mineralogy of fracture and vein fillings as potential records of water chemistry and microbial activity. In the coming months, water samples from basal-discharge streams, ice-margin lakes and melt-water pools forming on top of the ice sheet (Figure X) will be chemically characterized in multiple laboratories. Chemical analysis of water and rock samples will provide a basis for modeling water-rock reactions and predicting compositions of groundwater intersected during the drilling phase of the project anticipated for summer 2009. Lisa Pratt and Tullis Onstott will travel to Helsinki, Finland for participation in a site selection meeting for the Greenland Sub-Ice Sheet Borehole during October of 2008.

Methanogenesis and methane flux in permafrost environments

The methane detected in the Martian atmosphere is the only viable candidate to date for a potential signature of life. As a result, we have focused our efforts to improve our understanding of methanogenesis in permafrost environments on Earth by developing the instrumentation needed to characterize methane emissions in the field. During the last three years, support from NAI has been used to design and construct a portable Cavity Ringdown Spectrometer that is capable of determining the isotopic composition of methane in the Martian atmosphere. The current instrument is capable of methane carbon isotopic measurements in the field with twice the accuracy of the multipath laser spectrometer being sent on the Mars Science Lander mission. A recently funded proposal from NASA’s Mission Development Implementation Plan will facilitate upgrades of the instrument to enable hydrogen isotopic determinations. The upgraded instrument will allow us to measure the isotopic compositions of methane with a 10 fold improvement in accuracy. Field excursions to Axel Heiberg Island were undertaken in April 2008, allowing us to successfully test a commercial Cavity Ringdown Spectrometer to document methane flux from hot springs and permafrost environments.

Student Awards and Honors

We take particular pride in recognizing that Shannon Tronick (second year doctoral student at Princeton University) was awarded a NASA Harriet G. Jenkins Graduate Student Fellowship and Adam Johnson (third year graduate student at Indiana University) was awarded an Exobiology Summer Internship for study with Jeffrey Bada at Scripts Institution of Oceanography.