2011 Annual Science Report
University of Wisconsin Reporting | SEP 2010 – AUG 2011
The focus of the WARC Team is on the signatures and environments of life, and in Year 4, the team significantly expanded its research and Education and Public Outreach (EPO) efforts into new directions within this framework. Twenty-six research projects were pursued in Year 4, including 15 continuing projects and 11 new initiatives. EPO efforts in Year 4 also expanded, and ten major projects and programs were run through NASA-JPL and the University of Wisconsin.
Research Topic 1: Early surface conditions on Mars and Earth – Implications for Life
Four entirely new research projects for WARC were pursued in Year 4 that were aimed at determining the environments that existed on Mars and Earth between ~4.0 and 3.5 Ga, as well as the role that core formation has in providing conditions favorable to supporting life. WARC research in the previous year provided the ... Continue reading.
The period 2.7 to 2.5 b.y. ago, the period leading you to the Great Oxidation Event (GOE), is becoming increasingly recognized as a time of major environmental change. A holistic understanding of the changes that occurred in microbial ecology, and their effects of the environment, are only possible by integrating multiple geochemical proxies. By simultaneously looking at C, O, S, Fe, Mo, and Sr isotopes, we develop a picture of extensive oxygenic photosynthesis, but approximate balance with reduced resevoirs such as reduced Fe and reduced volcanic gases, such that free oxygen did not yet become abundant on the planet. Although many workers have questioned a rise in oxygenic photosynthesis significantly before the GOE, these new data clearly indicate that this metabolism was widespread at least 400 m.y. before the GOE.ROADMAP OBJECTIVES: 4.1 5.3 6.1 7.1 7.2
Project 5C: Growth of Ca-Mg Carbonates in the Presence of Dissolved Hydrogen Sulfide – in Situ and AFM Studies
Dissolved hydrogen sulfide, one of the major products of bacterial sulfate reduction can promote crystallization of Ca-Mg-carbonates and dolomite. Hydrogen sulfide can be adsorbed strongly on the surfaces of Ca-Mg-carbonates, which can catalyze dehydration of surface Mg-water complexes and promote Mg incorporation into the Ca-Mg-carbonates and dolomite.ROADMAP OBJECTIVES: 7.1 7.2
Project 5D: A Computational Study of Mg2+ Dehydration in Aqueous Solution in the Presence of Sulfide – Insights Into Dolomite Formation
Microbial activity has been invoked frequently in the literature to explain the formation of massive sedimentary dolomite at near-Earth’s surface temperatures in the ancient geological rock record and, more generally, for the formation of mixed cation carbonates. Carbonates have been found on Mars, and may serve as a biosignature, if the mechanisms of formation can be elucidated. Sulfide, the product of bacterial sulfate reduction, has been proposed previously to promote dolomite formation by facilitating desolvation of Mg2+ in solution and, thus, incorporation into the dolomite crystal structure. Chemical intuition, however, does not suggest any particular characteristic of HS- that would render it an efficient promoter of Mg2+ desolvation. We, therefore, conducted ab initio reaction path ensemble (RPE) and Molecular Dynamics simulations to determine the energy barrier for removal of a single water molecule from the first solvation shell compared to that for hydrated Mg2+ in the presence of HS- in the second coordination shell of Mg2+. We found that HS- had little, if any, effect on lowering the Mg2+ dehydration barrier in aqueous solution. Empirical observations of HS- promoted dolomite formation may then suggest a potential role for HS- in promoting Mg2+ desolvation at a solid precursor phase. Our project addresses NASA Astrobiology Institute’s (NAI) Roadmap goals of recognizing and preserving biosignatures and NASA’s Strategic Goal of advancing scientific knowledge of the origin and evolution of the Earth’s biosphere and the potential for life elsewhere.ROADMAP OBJECTIVES: 7.1
Project 2E: The ORGANIC Experiment on EXPOSE-R – Space Exposure on the International Space Station (ISS)
In March of 2009, the Organic experiment integrated into the European multi-user facility EXPOSE-R, containing experiments dedicated to Astrobiology, was mounted through Extra Vehicular Activity (EVA) externally on the International Space Station (ISS). The experiment exposed organic samples of astronomical interest for a duration of 97 weeks (~22 months) to the space environment. The samples that were returned to Earth in spring 2011, received a total UV radiation dose during their exposure including direct solar irradiation of >2500h (>42.1 kJ per sample, based on ASTM E-490 AM0 standard solar spectrum between 119 and 400 nm), exceeding the limits of laboratory simulations. The Organics experiment on EXPOSE-R consists of thin films of polycyclic aromatic hydrocarbons (PAHs) and fullerenes that were exposed to solar UV under vacuum or controlled atmosphere. Samples were deposited in thin (~few hundred nm) films by sublimation on MgF2 windows inside the sample cell. Dark samples are shielded from the UV photons and enable us to discriminate between the effects of exposure to photons and cosmic rays. The corresponding time-dependent ground-control for the Organic experiment measured over ~19 months is presented and preliminary data of returned flight samples are shown.ROADMAP OBJECTIVES: 3.1
Isotopic analysis of biologically important elements in petrographic context is a fundamental tool for astrobiology. Secondary ion mass spectrometry (SIMS) is a powerful tool used to understand biogeochemical processes at the spatial scale of the individual microorganisms that drive them. The benefits of the extremely high spatial resolution offered by SIMS do not come without costs, however. Unconstrained physical and chemical variables in the sample of interest can introduce biases leading to inaccurate measurements. Understanding and constraining these barriers to accuracy as we move towards ever finer spatial resolution and analytical precision is a primary focus at WiscSIMS.ROADMAP OBJECTIVES: 4.1 5.1 5.2 5.3 7.1
Mobile exploration of Mars so far has been achieved by the use of rovers, powered by solar panels or in the near future, radioisotope thermoelectric generators (RTGs). The JPL team has been contributing to an effort to develop an alternative source of locomotion, wind power. A Tumbleweed rover is a large (maybe as big as 20 ft diameter), inflatable structure, equipped with suitable instruments and would be able to make long-range surveys of large areas of Mars. A rover would carry a suite of science instruments for surface and near-surface interrogation and be released to roam for the duration of a season or longer. Although direction will be at the mercy of the wind, location will be tracked precisely and randomized surveys of a large area are equivalent to conventional coordinate grid sampling.ROADMAP OBJECTIVES: 2.1 7.1
Field research at Mars analogs sites such as desert environments can provide important constraints for instrument calibration and landing site strategies of robotic exploration missions to Mars that will investigate habitability and life beyond Earth during this decade. We report on astrobiology field research from the Mars Desert Research Station (MDRS) in Utah Hanksville conducted during the EuroGeoMars 2009 campaign. EuroGeoMars 2009 was an example of a Moon-Mars field research campaign dedicated to the demonstration of astrobiology instruments and a specific methodology of comprehensive measurements from selected sampling sites. Special emphasis was given to sample collection and pre-screening using in-situ portable instruments. We have investigated 10 selected samples from different geological formations including Mancos Shale, Morrison, and Dakota Formation as well as a variety of locations (surface, subsurface and cliffs) partly in-situ in the habitat or in a post-analysis cycle. We compiled the individual studies and tried to establish correlations among environmental parameters, minerals, organic markers and biota. The results are interpreted in the context of future missions that target the identification of organic molecules and biomarkers on Mars.ROADMAP OBJECTIVES: 2.1 5.1
We have continued to investigate the Río Tinto area an acid river in Spain analogous to the environment of early Mars. We are now using a sophisticated technique that analyses the three stable isotopes of oxygen and their relationship to each other with surprising results. Isotopic fractionation processes, change the relative proportions of the oxygen of masses 17 and 18 relative to 16 to an extent generally proportional to their mass difference, an approximately 2:1 effect for O-18 and O-17, respectively, shown by the slope of the line. Most terrestrial materials exhibit this same relationship perfectly, but oxygen in sulfate from waters and minerals in the Río Tinto area, produced by either microbial or inorganic processes, deviate from that: there is also the suggestion in preliminary data that these two processes can be differentiated from each other too. The measure of this relationship would provide a biosignature, independent of an measured oxygen isotope value of subsequent fractionation process.ROADMAP OBJECTIVES: 2.1 7.1
Project 5F: Roles of Extracellular Polysaccharides From Sulfate-Reducing Bacteria in Governing Dolomite Composition and Crystallization
Ca-Mg-carbonates ranging from Mg-calcite to Mg-dolomite can be synthesized in presence of extracellular polymeric substances (EPS) excreted by sulfate-reducing bacteria (SRB). The role of EPS in catalyzing dolomite formation is similar to the agar-bearing systems, because polysaccharides are the major components in EPS. Low-temperature dolomite and Ca-Mg-carbonates with continuous compositional variations between calcite and dolomite could be potential biosignatures, because they require catalysts like polysaccharides.ROADMAP OBJECTIVES: 7.1 7.2
In the fourth year of our NAI project, a series of free drift experiments and one chemo-stat experiment were completed to determine the effect of temperature, chemical composition, pCO2, pH and precipitation rate on the incorporation of Mg in calcite in relatively dilute solutions. These experiments will permit geochemical relationships to be established between carbonate minerals and the solutions from which they form to gain a better understanding of the origin and occurrence of carbonates in ancient terrestrial and extraterrestrial environments.ROADMAP OBJECTIVES: 4.1 7.1
The isotopic composition of Mg in carbonate is of interest to studies on paleo environments because of the potential for constraining temperatures, vital effects, and Mg fluxes associated with precipitation of carbonate minerals. Indeed, Mg isotope fractionation during inorganic carbonate precipitation is important because this serves as the baseline for interpreting the Mg isotope variations and inferred fluid isotope compositions for both abiogenic and biogenic carbonate. We report the results of Mg-bearing calcite synthesis studies used to constrain the fractionation of Mg isotopes during calcite precipitation. The results provide the baseline data needed to interpret Mg-bearing carbonates from the early Earth, as well as carbonates that are likely to be found on Mars.ROADMAP OBJECTIVES: 4.1 7.1 7.2
The production of magnetite as a byproduct of dissimilatory microbial iron oxide reduction (DIR) has been hypothesized to be an important pathway in the early diagenesis of chemically-precipitated sediments on early Earth, leading ultimately to the preservation of large quantities of magnetite in banded iron formations (BIFs). A significant fraction of the magnetite (and other Fe-bearing minerals such as siderite and pyrite) in BIFs is isotopically light, likely due to Fe isotope fractionation between biogenic Fe(II) and residual Fe(III) oxides. Only one modern environmental setting has reported possible in situ magnetite formation resulting from DIR: the Bay of Vidy in Lake Geneva, Switzerland. Previous work has characterized a widespread magnetic susceptibility anomaly in the Bay of Vidy sediments stemming from an influx of amorphous Fe(III) oxide from a nearby sewage treatment plant, and determined the presence of fine-grained magnetite apparently produced via DIR. In this study, we examined the Fe isotope composition of distinct pools of solid-phase Fe contained in sediments from the Bay of Vidy. Significant Fe(III) reduction has taken place, resulting in the reduction of nearly all reactive (non-silicate) Fe. Very little Fe isotope variation was observed within sediment Fe pools, including magnetite. The lack of sediment heterogeneity, along with the highly reduced nature of the sediments, suggests that DIR has carried through to completion in this deposit. The absence of spatial Fe redox gradients accompanying complete Fe(III) reduction has prevented the segregation of Fe isotopes during microbial reduction. This case study provides a basis for interpreting instances in the rock record where DIR was active but no Fe isotope fractionation was preserved.ROADMAP OBJECTIVES: 4.1 7.2
Experimental studies in geochemical systems analogous to ancient rock precursors are required to gain insight into the biogeochemical processes responsible for generating unique chemical or isotopic compositions in ancient rocks. We conducted a synthesis of prior and ongoing laboratory studies of Fe isotope fractionation during abiotic and biologically catalyzed (by dissimilatory microbial iron reduction, DIR) interaction between Fe(II) and Fe(III) oxide phases in the presence of dissolved silica, which was likely abundant in Precambrian oceans. In particular, previous studies of iron isotope fractionation during microbial reduction of an amorphous iron oxide-silica coprecipitate in high-silica, low-sulfate artificial Archean seawater were analyzed in combination with fractionation during abiotic Fe(II)-Fe(III) interaction to assess the rates and mechanisms of Fe isotope fractionation. The results show that although isotopic exchange rates were a function of solid and solution compositions, in all cases they were much higher than that determined in previous studies of aqueous Fe(III) and ferrihydrite interaction, highlighting the importance of electron exchange in promoting Fe atom exchange. When compared to analogous microbial reduction experiments with overlapping Fe(II) to Fe(III) ratios, isotopic exchange rates are faster in the biological experiments, likely due to promotion of atom exchange by the solid-phase Fe(II) produced during DIR. These findings provide constraints on the range of equilibrium iron isotope fractionations that may be produced by different geochemical processes. In addition, when interpreted in a Fe mass-balance context, our findings provide strong support for DIR as a mechanism for producing Fe isotope variations observed in Neoarchean and Paleoproterozoic marine sedimentary rocks.ROADMAP OBJECTIVES: 4.1 7.1
Project 4A: Characterization of Novel Solid-Phase Fe(II)-Oxidizing Chemolithotrophic Bacteria From Subsurface Environments
Ferrous iron (Fe(II)) can serve as an energy source for a wide variety of chemolithotrophic microorganisms (organisms that gain energy from metabolism of inorganic compounds). Fe(II) oxidation may have played a role in past (and possibly, present) life on Mars, whose crust is rich in primary Fe(II)-bearing silicate minerals, as well as Fe-bearing clay minerals formed during weathering of primary silicates. This project examined the physiological and phylogenetic properties of novel solid-phase Fe(II)-oxidizing bacteria (FeOB) isolated from subsurface sediments from the Columbia River basin in eastern Washington, as well as clay-rich subsoils from Madison, WI. The organisms were enriched using biotite (a Fe(II)-bearing primary silicate mineral) as an energy source, and purified on organics-containing medium. The capacity of the isolates to oxidize soluble and solid-phase Fe(II) compounds was assessed, and the 16S rRNA gene sequence for each of the isolate was determined. The results revealed that a wide variety of Proteobacteria are capable of catalyzing solid-phase Fe(II) oxidation, including several groups of organisms not previously known as FeOB. These results confirm and expand our knowledge of solid-phase chemolithotrophic Fe(II) oxidation on Earth, and bolster the concept of mineral-associated Fe(II) oxidation as a potential basis for microbial life on other terrestrial planets.ROADMAP OBJECTIVES: 3.2 5.1
Project 1B: U-Th-Pb Geochronology and Fe Isotopes of the 3.4 Ga Marble Bar Chert Indicates Early Anoxygenic Photosynthesis
The origin of the spectacular red jasper (hematite+chert) at Marble Bar, Australia, has been a subject of debate for decades. Previous work has argued that oxidation occurred at the time of deposition 3.5 b.y. ago, and that the mechanism of oxidation was free oxygen in the atmosphere. This in turn would indicate that oxygenic photosynthesis had evolved by 3.4 Ga. By measuring Fe isotopes in the jasper, we can show that oxidation was extremely limited, and U-Th-Pb isotope geochronology on the same samples shows that the jasper precipitated form U-poor ocean water. This in turn indicates that there was no free oxygen in seawater at the time of deposition of the jasper. This in turn suggests that the mechanism was more likely to have been an anaerobic process, such as anoxygenic photosynthetic Fe(II) oxidation.ROADMAP OBJECTIVES: 4.1 6.1 7.1
Rb-Sr geochronology on martian meteorite ALH8400 reveals that an igneous-textured zone within the meteorite yields a mineral isochron consistent with a young 4.1 Ga age for igneous crystallization. In contrast, a mineral isochron from a carbonate-rich zone in the meteorite defines an age of 3951 Ma, which is concordant with the time of carbonate formation and is interpreted as a shock-resetting event. Carbonate from the rock has unusually high initial 87Sr/86Sr ratios and such high ratios require interaction with that were derived from weathered bedrock that had high Rb/Sr, most likely clay alteration products. This places a powerful constraint on the timing of clay weathering on Mars at >4.0 Ga.ROADMAP OBJECTIVES: 2.1
Using new protocols developed at WiscSIMS, we made in situ measurements of three stable isotopes of sulfur (32S, 33S and 34S) in pyrite from the Meteorite Bore Member with unprecedented small spot sizes and accuracy (Williford et al. 2011). We have found a moderate range of S-MIF (> 1‰) in authigenic pyrite before, during and after the Early Proterozoic glaciation as well as a 90‰ range of mass dependent sulfur isotope fractionation (δ34S) larger than any observed in sediments older than 700 Ma. Furthermore, abundant detrital pyrite preserved in one glacial sandstone unit from the Meteorite Bore Member exhibits a range of mass-independent sulfur isotope fractionation slightly larger than the largest published range, from 2.5 Ga sediments of the Hamersley and Transvaal Basins (> 15‰), suggesting that these detrital grains may have originated in rocks of similar age. Taken together, these data imply that the Meteorite Bore Member was deposited during the transitional interval when atmospheric oxygen had risen sufficiently for enhanced continental weathering and ocean sulfate to occur, yet remained low enough to permit the preservation of detrital pyrite and moderate S-MIF.ROADMAP OBJECTIVES: 1.1 4.1 4.2 7.1
Project 3A: Stable Isotope and Mineralogical Studies of Banded Iron Formations – O and Si Isotopes by SIMS
We have studied the mineralogy and microscopic textures of four banded iron formations (BIFs): Isua, Greenland (3.8 Ga); Hamersley, Western Australia (2.5 Ga); Transvaal, South Africa (2.5 Ga), and Biwabik, Minnesota, USA (1.9 Ga). These rocks have been interpreted to preserve records of conditions and chemistry of Precambrian oceans. This hypothesis is evaluated with in situ SIMS analysis of oxygen (δ18O) and silicon isotope ratios (δ30Si) in chert domains within the BIFs. The paragenesis of magnetite and hematite is important to understanding the fluid and thermal history of unmetamorphosed or low-temperature (sub-greenschist facies) oxide-facies BIFs. We identified silician (up to 3 wt% SiO2) magnetite overgrowths in samples of the Dales Gorge BIF from Wittenoom. We hypothesize that silician magnetite is stabilized by organic matter and thus is a biosignature. We investigated the distribution of δ18O values in quartz, magnetite, silician magnetite, and hematite by SIMS and found that while quartz is homogeneous (average δ18O = 22.0 ±1.3‰ 2SD, VSMOW), values of δ18O for magnetite and hematite vary by 13‰ (-5 to +7‰) and are correlated with different generations of magnetite and hematite.ROADMAP OBJECTIVES: 4.1 5.2 7.1
Project 2D: Establishing Biogenicity and Environmental Setting of Precambrian Kerogen and Microfossils
Stable carbon isotope ratios preserved in ancient organic matter provide valuable information about the origin and evolution of metabolic pathways, and the evolution of the carbon cycle in general. In situ carbon isotope analysis allows organic matter to be measured in petrographic context. The microtexture and spatial relationship of sedimentary organic matter and its mineral matrix offers clues about source and diagenetic history – essential elements in the interpretation of isotopic data. We have developed protocols with the IMS-1280 ion microprobe to analyze carbon isotope ratios in organic matter with a spot size of 1–10 μm. A suite of new standards allows correction of matrix effects due to variable chemical composition. Four suites of Proterozoic microfossils of uncontested biogenicity have been analyzed, showing distinct values of δ13C that correlate with taxonomy and metabolism (Williford et al. 2011a in prep). Studies of kerogen and pyrobitumen from 2.7–2.5 Ga sediments support prior conclusions about differential impacts of aerobiosis and methane metabolisms in shallow versus deep-water depositional environments and reveal a degree of isotopic heterogeneity obscured by conventional, bulk analyses (Williford et al, 2011b in prep). Analysis of organic matter from the 3.35 Ga Strelley Pool Chert yield low and consistent values of δ13C, consistent with a biogenic origin (Lepot et al. 2011, in prep).ROADMAP OBJECTIVES: 4.1 7.1
Project 2C: Role of Extracellular Polymeric Substances (EPS) and Bacteria Cell Wall Structure in Shielding Against Specific Mineral Toxicity – Implications for Cell Surface Evolution
Our interdisciplinary project examined the hypotheses that (1) bacterial cell membranes are ruptured in contact with specific mineral surfaces, (2) biofilm-forming extra-cellular polymeric substances (EPS) may have evolved to shield against membrane rupture (cell lysis), (3) differences in cell-wall structure of Gram-negative and Gram-positive bacteria may influence the susceptibility of cells to toxic minerals and (4) mineral toxicity depends on its surface chemistry and nanoparticle size.
Previously, we have examined Gram-negative P. aeruginosa strains, wild-type (PAO1) that is capable of generating copious amount of EPS and producing biofilms, as well as the knock-out mutant (Δ-psl) that is defective in its ability to form EPS and biofilms. In the 2010-2011 year of funding, we have expanded our study to include Gram-positive B. subtilis strains, biofilm-producing wild-type NCIB3610 and biofilm-defective mutant yhxBΔ. We confirmed the hypotheses (1), (2) and (4) for both Gram-negative and Gram-positive bacteria, with toxicity increasing as amorphous β-TiO2 < γ-Al2O3. We also confirmed hypothesis (3) that Gram-positive bacteria are less susceptible to mineral toxicity than Gram-negative because of the most robust cell-wall structure of the former. Finally, we have shown that the mechanisms of toxicity depends on mineral surface charge for initial adhesion of nanoparticles to the cell surface, nanoparticle size which determines whether the particles can enter the intracellular space (e.g., for γ-Al2O3), the presence of surface free radicals (e.g., β-TiO2 ) which would have been generated by UV-radiation and meteorite impacts on early Earth, Mars, and other worlds.
By understanding the mechanisms for membranolysis, especially under the extreme conditions of high radiation and heavy impacts during early planetary history, the project addresses the NASA Astrobiology Institute’s (NAI) Roadmap goals of understanding the origins of cellularity, the evolution of mechanisms for survival at environmental limits, and preservation of biosignatures, and NASA’s Strategic Goal of advancing scientific knowledge of the origin and evolution of the Earth’s biosphere and the potential for life elsewhere.ROADMAP OBJECTIVES: 3.4 5.1 7.1
Metal oxides have been studied widely in the biogeochemical literature for understanding the adsorption and other surface interactions of dissolved organic and inorganic molecules with mineral surfaces. The goal of our study is to understand whether the earliest lipid membranes or “protocells” would have been stable in contact with different mineral surfaces on early Earth, and whether the surface properties of the minerals control their relative affinity to cell membranes. In previous years of this study, we used bulk adsorption isotherms and classical DLVO theory modeling approaches to examine the stability lipid bilayers in contact with micron-sized quartz (α-SiO2), rutile (α-TiO2) and corundum (α-Al2O3) particles. By understanding the role of natural geochemical parameters such as mineral surface chemistry, solution chemistry and temperature cycling on protocell membrane stability, we attempted to model potential aqueous environments where life may have originated such as lacustrine, tidal pool, and sub-aerial or submarine hydrothermal vents. In the present project year, we used neutron reflectivity to determine if the geometry of the mineral surface (sub-spherical particles versus planar single crystal surfaces) affects membrane stability. The results of our various approaches were consistent showing that lipid membrane stability depends on (1) lipid head-group charge and (2) surface charge of the mineral, which in turn depend on pH, ionic strength, presence or absence of Ca2+, (3) van der Waals interactions, and (4) relative hydrophobicity of the surface, as well as purely physical parameters such as relative size of the model membrane relative to the mineral surface. Our project addresses NASA Astrobiology Institute’s (NAI) Roadmap goals of understanding the origins of cellularity and the evolution of mechanisms for survival at environmental limits, and NASA’s Strategic Goal of advancing scientific knowledge of the origin and evolution of the Earth’s biosphere and the potential for life elsewhere.
Keywords: lipid, protocell, vesicle, self-assembly, pre-biotic, mineral surface, hydrophilic, hydrophobic, bilayerROADMAP OBJECTIVES: 3.4 5.1
Project 2A: Estimation of Pre-Biotic Amino Acids Delivery to Earth by Carbonaceous Chondrite Meteorites
The role of mineral surfaces in extraterrestrial organic synthesis, pre-biotic chemistry, and the early evolution of life remains an open question. Mineral surfaces could promote synthesis, preservation, or degradation of chiral excesses of organic small molecules, polymers, and cells. Different minerals, crystal faces of a mineral, or defects on a face may selectively interact with specific organics, providing an enormous range of chemical possibilities. We focus here on amino-acid isomer adsorption, conformation, and racemization on minerals representing primitive and altered peridotite found in chondritesand on planetary bodies. The study is inspired by the discovery of an excess of L-isovaline, a non-biologic amino acid, in a few carbonaceous meteorites by (Glavin and Dworkin, 2009), which suggests that the chiral nature of biology may have been due to excess L-amino acids delivered pre-biotically by meteorites.
In the present year of funding, we expanded our study to determine the conformation and binding modes of the acidic amino-acids, glutamate (Glu) and aspartate (Asp), adsorbed on model oxide, γ-Al2O3, using Attenuated Total Reflectance-Fourier Transform Infra-Red Spectroscocpy (ATR-FTIR) and the Triple Layer surface complexation model fits to bulk adsorption data over a wide range of pHs and amino-acid concentrations.
We also examined adsorption of L- and D- Glu, Asp, and a non-biological; amino acid, iso-valine on peridotite and serpentinte as pristine and altered analogs of carbonaceous chondrites, using LC-FD/ToF-MS. Preliminary results do not indicate preferential adsorption of either L- or D-amino-acids on peridotite and serpentinite, within detection limits. More detailed studies are required to improve the sensitivity and accuracy of the experiments involving the chiral amino-acids adsorption on chondritic analog materials.
The project addresses NASA Astrobiology Institute’s (NAI) Roadmap Goal 3 of understanding how life emerges from cosmic and planetary precursors , and Goal 4 of understanding organic and biosignature preservation mechanisms. The work is relevant to NASA’s Strategic Goal of advancing scientific knowledge on the origin and evolution life on Earth and potentially elsewhere, and of planning future Missions by helping to identify promising targets for the discovery of organics.ROADMAP OBJECTIVES: 3.1 3.2 4.1
We investigated the effect of evolution of the Earth’s core on the magnetic field, which bears on the extent of magnetic shielding of cosmic radiation, which in turn has implications for the evolution of life. We hypothesize that extensive magnetic shielding likely occurred only after turbulent flow in the liquid outer core subsided, which would have occurred after 1 or 2 b.y. of inner core solidification, allowing differential rotation of the inner and outer core. These results suggest that life which evolved in the first 1 to 2 b.y. of Earth history would have had to develop strategies to cope with high cosmic radiation. The most effective strategy is to use shielding by absorption of radiation by water. Consequently evolution of life on the surface of the Earth occurred much later in the Earth’s history.ROADMAP OBJECTIVES: 1.1 4.1
Project 1C: U-Th-Pb Geochronology of the 3.4 Ga Apex Basalt Suggests an Anoxic Early Earth Atmosphere
Direct determination of the age of oxidative weathering in ancient rocks is difficult, but bears on when the surface environments of the Earth contained free oxygen, which in turn constrain when oxygenic photosynthesis was sufficient to overwelm reduced sinks for oxygen. It has been proposed that oxidized zones of the 3.4 Ga Apex Basalt in the Pilbara Craton formed in the Archean, at least 2.8 b.y. ago, and possibly as old at 3.4 b.y. ago. However, application of U-Th-Pb geochronology to these rocks indicate that oxidation was recent, probably within the last 200 m.y., reflecting deep Phanerozoic weathering that occurred across Australia. The oxidized zones therefore do not reflect the presence of free oxygen in the Archean.ROADMAP OBJECTIVES: 4.1 7.1
Project 5E: Disordered Dolomite Crystallization From Media Containing Agar Gel and Halophilic Bacteria
Ca-Mg-carbonates ranging from Mg-calcite to Mg-dolomite can be synthesized in presence of halophilic bacteria with agar media and agar media only. Extracellular polysaccharides adsorbed on surfaces can catalyze dolomite formation because of strong hydrogen bonding between the polysaccharides and the carbonate surface. This study provides insight into the effect of similar polysaccharides produced by microorganisms on dolomite formation. Low-temperature Ca-Mg-carbonate solid solution with continuous composition between calcite and dolomite could be a potential biosignature, because it requires catalysts like polysaccharides.ROADMAP OBJECTIVES: 7.1 7.2
Project 7B: Development of a Laser Ablation, Electron-Impact Miniature Mass Spectrometer (LA-EI-MMS) for in Situ Chemical and Isotopic Composition and Age Determinations of Martian Rocks
A prototype of laser ablation-miniature mass spectrometer (LA-MMS) instrument for geochemical and age dating of rocks on the surface of extraterrestrial bodies is being developed in this project. In the LA-MMS method the rock sample is ablated by a laser and the neutral species produced are analyzed using the JPL-invented MMS. The neutral atoms ablated by a pulsed laser from the rock are ionized by electron impaction; the resulting ions of different masses are then spatially dispersed along the focal plane of the magnetic sector of the miniature mass spectrometer (MMS) and measured in parallel by a modified CCD array detector capable of detecting ions directly. Chemical analysis and high precision isotope ratios of elements have been measured in various rock samples by LA-MMS. Work on the measurement of absolute age of these rock samples based on K-Ar radiogenic technique is in progress.ROADMAP OBJECTIVES: 2.1 7.2
Arizona State University
Carnegie Institution of Washington
Georgia Institute of Technology
Massachusetts Institute of Technology
Montana State University
NASA Ames Research Center
NASA Goddard Space Flight Center
NASA Jet Propulsion Laboratory - Icy Worlds
NASA Jet Propulsion Laboratory - Titan
Pennsylvania State University
Rensselaer Polytechnic Institute
University of Hawaii, Manoa
University of Wisconsin
VPL at University of Washington