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Amino Acid Preservation in Saline-Lake Sediments and Mars-Simulant Regolith
Project Investigators: Lisa Pratt
Other Project Members
Adam Johnson (Doctoral Student)Jeffrey Bada (Collaborator)Summary
Potentially habitable environments on the Martian surface have been identified by orbital spectroscopy and by landed instruments on the Mars Exploration Rovers (MERs). Identification of evaporite mineral assemblages on Mars provides strong evidence for the widespread role of evaporitic water bodies of water in the past. Evaporite minerals may provide enhanced preservation of biomolecules by sequestration of organic constituents into mineral matrices during crystallization. The utilization of amino acids, the building blocks of proteins, as a distinct biosignature that could be extracted from evaporite phases would provide a strong biosignature for life having existed in the past or persisting to the present on Mars.
Astrobiology Roadmap Objectives:
- Objective 2.1: Mars exploration
- Objective 3.2: Origins and evolution of functional biomolecules
- Objective 5.1: Environment-dependent, molecular evolution in microorganisms
- Objective 5.3: Biochemical adaptation to extreme environments
- Objective 7.1: Biosignatures to be sought in Solar System materials
Project Progress
Experiments were carried out to mimic the present Martian diurnal cycling of a Mg-Fe-Ca-Na-SO4 brine derived from acidic weathering of olivine-laden basalt. Experimental brines were laced with an enantiomeric excess of amino acids. Testing was done with and without exposure to the photolytic effects of UV radiation and utilizing a diurnal temperature cycle suitable for simulation of evaporation and sublimation processes in a Martian paleolake or permafrost system.
Results indicate that iron containing brines in the presence of UV are prone to increased levels of amino acid degradation due to photo-Fenton oxidation reactions. In the absence of UV, iron-rich brines provide enhanced preservation, with half lives 200-300% longer than systems lacking iron. Racemization half lives are 30 and 50 times greater than corresponding degradation half lives in iron and non-iron samples, respectively. These initial results provide interesting scenarios in the preservation of organic matter on Mars; an iron-rich subsurface groundwater system, such as those attributed to hematite concretion formation, may provide increased organic matter preservation. Additionally, a limiting factor in life detection may not be the detection of an enantiomeric excess of amino acids but detecting a pool of amino acids at all.
In addition to laboratory brines, we are studying a hydrologically closed basin system in southern California as a Mars analog environment. Samples from a long sediment core (30 meters) drilled at Soda Lake in the Carrizo Plain are being analyzed to determine the yield of enantiomeric excess of amino acids in lacustrine sediments dominated by interbedded clay- and sulfate-mineral assemblages. Obtained values will provide rates of amino acid racemization in environments dominated by seasonal to decadal cycles of evaporation and precipitation of sulfate and chloride minerals.
Experimental brines containing amino acids can be seen inside a Mars simulation chamber. Some samples are exposed to ultraviolet radiation and other samples are in a radiation shadow.Mission Involvement
MSLDetection of complex organic molecules, including amino acids and peptides, is a key goal of MSL. The experimental precipitates and sediment samples being analyzed in the amino acid project enhance our understanding of the types of mineral deposits likely to be encountered at sulfate-rich sites on Mars.- Amino Acid Preservation in Saline-Lake Sediments and Mars-Simulant Regolith
- Application of U-tube and fiber-optic distributed temperature sensor to characterize the chemical and physical properties of a deep permafrost and sub-permafrost environment at High Lake, Nunavut, Canada.
- Challenges for Coring Deep Permafrost on Earth and Mars: Drilling Project at High Lake, Nunavut, Canada
- Design, construction and testing of a Cavity-Ring Down Spectrometer for determination of the concentration and isotopic composition of methane
- Environmental genomics reveals a single species ecosystem deep within the Earth.
- High Lake Gossan deposit: An Arctic analogue for ancient Martian surficial processes?
- Isotopic Signatures of Methane and Higher Hydrocarbon Gases from Precambrian Shield Sites: A Model for Abiogenic Polymerization of Hydrocarbons
- Mars Forward Contamination Studies Utilizing a Mars Environmental Simulation Chamber
- Microbial Communities in Subpermafrost saline fracture water at the Lupin Au Mine, Nunavut, Canada
- Radiolytic oxidation of sulfide minerals as a source of sulfate and hydrogen to sustain microbial metabolism
- Saline Lakes and Gypsum Dunes in the Rio Grande Rift System as Analogues for Sulfate Deposits on Mars
- Stability of methane hydrates in the presence of high salinity brines on Mars
- The Diversity of the Original Prebiotic Soup: Re-Analyzing the Original Miller-Urey Spark Discharge Experiments