2010 Annual Science Report
University of Wisconsin Reporting | SEP 2009 – AUG 2010
The signatures and environments of life are the primary focal points of research and EPO activities of the Wisconsin Astrobiology Research Consortium (WARC). In Year 3, WARC expanded its research portfolio beyond what was originally proposed to encompass all seven goals of the Astrobiology Roadmap. Nineteen research projects were pursued, as well as five Education and Public Outreach (EPO) projects. Research efforts involved 10 primary investigators, eight research scientists and staff, nine post-docs, eight graduate students, four undergraduate students, and 19 collaborators at other institutions. WARC members have research and EPO collaborations with seven other NAI teams, including NASA-Ames, the two NASA-JPL teams, Carnegie, Montana State, NASA-Goddard, and Penn State. Along with an expansion of research projects in Year 3, EPO activities also expanded; lead by our two EPO PIs, additional WARC personnel involved in EPO activities included six research PI’s, three post-docs, eight graduate students, and 43 undergraduate students. Major EPO events were held in Wisconsin, California, Georgia, Idaho, Hawaii, New Jersey, New York, Tennessee, and Texas. Several WARC EPO efforts were coordinated with other NAI teams, including both JPL teams and the Emeritus team at SETI.
Research efforts in Year 3 may be broadly grouped into five components: 1) organic compounds, including their preservation and interactions with minerals; 2) chemical and mineralogical biosignatures; 3) isotopic biosignatures; 4) new frontiers in analytical methods; and 5) Mars-related studies. These were tied into the goals of the Astrobiology Roadmap (AR) as follows: Eighteen projects had AR Goals 7.1 and 7.2 (biosignatures) as a major component, followed by eleven projects with AR Goals 4.1, 4.2, and 4.3 (Earth’s early biosphere; complex life; extraterrestrial effects) as a focus, next followed by seven projects connected to AR Goal 2.1 (Mars exploration), followed by six projects that pursued AR Goals 5.1 and 5.2 (molecular evolution; evolution of microbial communities). In addition, four projects were pursued that addressed AR Goals 3.1, 3.3, and 3.4 (prebiotic materials, origins of energy and cellularity), three projects involved work related to AR Goals 6.1 and 6.2 (environmental change, evolution of life), and one project focused on AR Goal 1.1 (habitable planets). The following is a summary of these efforts:
1. Organic compounds
The nature and preservation of organic compounds in the universe bears on the search for life elsewhere. In addition, interactions between organic compounds and minerals were likely key to early cell development, as well as defining the processes that produce biominerals that may be found in the rock record. In Year 3, WARC research pursued these themes in four projects. First, Pascale Ehrenfreund continued her studies of the survivability of organic compounds such as polycyclic aromatic hydrocarbons (PAHs), fullerenes, and macromolecules upon exposure to space environments using the EXPOSE-R facility on the International Space Station (ISS). Ehrenfreund’s experiments began in March 2009, and these compounds will be exposed to solar UV for ~18-24 months under vacuum or a controlled atmosphere. In addition, Ehrenfreund worked on development of a UV-visible spectrometer for in situ measurements of organic compounds on future free-fliers and lunar surface exposure facilities. This work is related to the NASA Organism/Organic Exposure to Orbital Stresses (O/OREOS) mission, scheduled to launch in late 2010. A second WARC project on organic compounds was directed by Nita Sahai, who has been working on novel methods for creating proto-cell membranes through interactions of phospholipid vesicles with mineral surfaces. Sahai found that the stability of proto-cell membranes is dependent upon mineral surface and lipid bilayer charges, solution composition, temperature cycling, and other factors. A third WARC project, also directed by Sahai, centered on the hypothesis that extra-cellular polymeric substances (EPS) evolved as an “armor” against cell membrane rupture upon cell-mineral interactions. Sahai showed that exclusion or incorporation of nano-minerals into cells was dependent upon surface charges of the minerals, but that production of EPS does indeed appear to facilitate mineral exclusion from cell membranes, preventing lysis of the cells (Figure 1). A fourth WARC project on organic compounds involved Huifang Xu and Eric Roden, who studied the effects of EPS on catalyzing dolomite formation, a mineral difficult to precipitate in the laboratory, but common in the geologic record. They found that EPS analogs lower the energy of dehydration of Mg in solution, a critical step in forming dolomite, enhancing dolomite precipitation. These results provide important insights into the mechanisms by which organisms may enhance dolomite formation.
Figure 1 near here.
2. Chemical and mineralogical biosignatures
There is little doubt that microbes may catalyze chemical and mineralogical changes in the environment that may be preserved in the rock record. Distinguishing minerals that form abiologically from those that exclusively form by biological processes, however, is a more difficult task. WARC research on chemical and mineralogical biosignatures in Year 3 was pursued in four projects. First, Eric Roden studied microbial oxidation of Fe(II) in basalt, the most common rock type on the rocky planets, coupled to nitrate reduction. These results suggest that a biological pathway is possible for producing the Fe(III)-bearing clays that have been identified on the surface of Mars. A second WARC project was pursued by Chris Romanek, who has investigated mechanisms for producing Mg calcite as a potential biosignature. Mg calcite is commonly produced by organisms, where it has been hypothesized that they may catalyzed Mg dehydration in solution, enhancing Mg calcite precipitation. Romanek, however, showed that if nucleation barriers are decreased by using calcite seed crystals, Mg calcite (up to 10 mol %) overgrowths may be produced entirely abiologically. This work is extending into Mg isotope studies to see if unique Mg isotope fractionations are produced as a function of formation pathways. A third project was led by Nita Sahai, which looked at the role of peptides in promoting hydroxyapatite formation. Late Precambrian exoskeletons may be composed of Ca phosphate and not calcite, suggesting that hydroxyapatite may have preceded calcite as a biomineral during the rapid rise of multicellular life at the end of the Precambrian. Sahai found that the random coil conformation of certain peptides are key to promoting hydroxyapatite formation. The insights into Ca phosphate biomineralization gained by this work also demonstrates a connection between astrobiology and the fast-growing field of medical mineralogy. Finally, a fourth WARC project pursued under this topic was led by Huifang Xu, who investigated potential geologic/tectonic sources for hydrogen that might sustain a deep biosphere. Xu found that the piezoelectric effect for quartz, where mechanical energy may be converted into chemical energy, producing hydrogen through water disassociation, is a potential mechanism for supporting hydrogen-based microbial communities in the deep biosphere.
3. Isotopic biosignatures
Perhaps the most important biosignature for life on Earth is the presence of free oxygen in the atmosphere, given the fundamental chemical disequilibrium that this presents when considered against the reduced interior of the planet. A commonly proposed time for the rise of free atmospheric oxygen is between 2.4 and 2.2 Ga, but this has always been problematic due to evidence for significantly earlier development of oxygenic photosynthesis. In Year 3, Clark Johnson and Brian Beard led a study that combined Mo and Fe isotopes in shallow marine Ca-Mg carbonates from the Transvaal basin, South Africa (2.65 to 2.5 Ga in age), and they found that the co-variation in these isotope systems provides a unique constraint on atmospheric oxygen contents. They calculated that free oxygen contents in the photic zone were at least 100 times higher than previously suggested at this time, indicating a significant increase in free oxygen prior to the Great Oxidation Event (GOE), or earlier so-called “whiff” events at 2.5 Ga. In a second project, Johnson and Beard studied C, O, Fe, and Sr isotopes in the same banded iron formation (BIF) carbonates from the 2.5 Ga Kuruman Iron Formation (South Africa). They found that none of the iron-rich carbonates have isotopic compositions that match those expected for 2.5 Ga seawater, indicating a dominant control by microbial processes; these results indicate that iron-rich BIF carbonates cannot be used to infer past seawater compositions, or make inferences on ancient CO2 contents of the atmosphere. A third WARC project pursued under this theme by Roden, Johnson, and Beard focused on Fe isotope fractionations produced by microbial Fe(III) reduction under conditions that better simulate those of Archean marine environments (low sulfate, high dissolved silica) relative to previous work. Surprisingly, these results showed that significantly greater quantities of isotopically light Fe were produced in these complex systems, and these results provide powerful arguments that microbial iron reduction was an important process in the Archean oceans. A fourth project was led by John Valley, who looked at Si and O isotope variations in cherts from BIFs of a variety of ages (Figure 2), from 3.8 to 1.8 Ga, using SIMS techniques. Valley showed that SIMS analysis of BIF cherts reveals fine-scale isotopic variations for Si but not for O, and these results suggest that Si isotopes may be a more robust indicator of chert genesis than O isotopes. Finally, a fifth WARC project, also led by Valley, involved in situ SIMS analysis of S isotopes in Archean and Proterozoic sulfides from the Pilbara craton. This work in part was aimed at constraining formation temperatures of the cherts, but in situ analysis demonstrated that no sulfides formed in S isotope equilibrium, indicating a complex history for the cherts. In addition, Valley applied in situ SIMS analysis approaches to pyrite from the Meteorite Bore glacial diamictite, which was deposited about the time of the GOE, and found very large ranges in S isotope compositions on fine scales. These results suggest a much larger fractionation in S isotopes by microbial sulfate reduction than would be indicated based on bulk analysis, which in turn suggests greater levels of seawater sulfate through the GOE than previously thought, providing further evidence for an early oxygenation of marine environments.
Figure 2 near here.
4. New frontiers in analytical methods
Two projects were pursued by WARC researchers in Year 3. First, Valley continued work on developing new approaches for in situ SIMS analysis of stable isotopes. A major finding was a strong effect of crystal orientation for O and S isotope analyses of certain minerals. This suggests that for some minerals, measured data may be incorrect if analysis conditions are not carefully adjusted. In addition, significant breakthroughs were made in achieving very small spots sizes, where data of reasonable precision can now be attained with micron-size spots, allowing assessment of complex mineral histories. Second, Mahadeva Sinha and Brian Beard continued work on developing a miniature mass spectrometer that is intended for in situ chemical and isotopic measurements, as well as geochronological work, on other planetary bodies such as Mars (Figure 3). Major breakthroughs for Year 3 included better control of ion generation during laser ablation and a substantial reduction in mass interferences in the ion source. In addition, analysis of natural samples began in Year 3, demonstrating the accuracy of the approach.
Figure 3 near here.
5. Focus on Mars
WARC research that is specifically targeted at Mars increased in Year 3. Ehrenfreund participated in Crew #77 at the Mars Desert Research Station (MDRS) in Utah. MDRS is a habitat complex for a 6-person crew, and Crew #77 collected soil samples for in situ spectroscopic studies and analysis of microbial communities. This work was intended to test specific instrumentation in the field, as well as life detection protocols. In a second Mars-related project, Max Coleman continued research on Rio Tinto, which has often been used as an analog for acid-sulfate weathering on Mars. In Year 3, Coleman showed that airborne remote sensing could be used to distinguish zones of microbial sulfide oxidation from zones of Fe(II) oxidation, based on distinct spectral characteristics associated with changes in iron speciation in Rio Tinto waters (Figure 4). The recognized importance of Mg sulfate minerals on Mars led Brian Beard to begin Mg isotope fractionation studies of epsomite. These results showed that Mg isotope fractionation during epsomite precipitation has little temperature dependence, making it an ideal isotope system to apply to Mars where past temperatures are uncertain. Moreover, the lack of temperature dependence makes Mg isotopes highly sensitive to the extent of evaporation and hence an indicator of paleo aridity. Finally, a fourth WARC project related to Mars that was pursued in Year 4 was aimed at revisiting the age of Mars meteorite ALH84001. The questions surrounding this meteorite helped establish the NAI, but, remarkably, its formation age has remained poorly constrained. Early work suggested an age of ~4.5 Ga. Taking a new approach, Beard showed that Lu-Hf geochronology avoids the alteration problems of earlier attempts to date ALH84001, providing a well-constrained formation age of 4.09 Ga; this significantly younger age fits much better into most models for early Mars evolution.
Figure 4 near here.
6. Education and public outreach (EPO)
Five EPO projects were pursued in Year 3 by Kay Ferrari and Brooke Norsted. WARC was a major participant in a Solar System Educator Astrobiology Institute workshop at NASA Ames, where 21 Solar System Educators (SSE) from 18 states and Puerto Rico participated. These educators are master teachers who train with various NASA groups to bring instructional materials into K-12 classrooms. Eight Astrobiology educator workshops were run for Solar System Educators in Year 3 in Idaho, Hawaii, New Jersey, New York, and Tennessee. In addition, 235 Solar System Ambassadors events were run throughout the year, reaching a total of 93,296 participants. WARC held its second “Astrobiology in the Ballpark” event, which is tied to a home game for the Madison Mallards (Figure 5), and over 5,500 people attended the event in Year 3. In addition to participating in the SSE program, WARC held a series of “Afterschool Science Nights” in Madison that had astrobiology as its theme; over 400 people, including parents and students, participated in eight elementary school events. WARC also participated in training sessions for the Imagine Mars Project via the UW Center for Biology Education ARMS (Adult Role Models in Science) initiative; 80 people were trained in astrobiology education who will then lead after school science clubs in the greater Madison area. In addition, WARC EPO staff brought Imagine Mars to 20 second- and third-grade elementary school students in an eight week summer session.
Figure 5 near here.
7. Field Sites
Five general field sites were associated with WARC research in Year 3. Project 2A (microbial iron oxidation of basalt; Eric Roden) involved basalt samples from Kilauea, Hawaii. Projects 3A and 3B (Fe and Mo isotopes as a constraint on past oxygen, and banded iron formation carbonates; Clark Johnson and Brian Beard) involved field sites in the 2.5-2.7 Ga Transvaal Basin of the Kapvaal Craton, South Africa. Projects 3D and 3E (O and Si isotope studies of banded iron formations and cherts, S isotope studies of Meteorite Bore diamictites and early Archean cherts; John Valley) involved several field sites in the 2.4-2.5 Ga Hamersley Basin and 3.4 Ga North Pole Dome, Pilbara Craton, Australia. The Utah Mars Desert Research Station (MDRS) was used for Project 5A (testing Mars-related instrumentation; Pascale Ehrenfreund). Finally, Project 5B (calibration of remote sensing results with measured aqueous iron speciation; Max Coleman) was done at Rio Tinto, Spain.
8. Mission Involvement
In Year 3, WARC was involved in two active missions, and one mission in the long-range planning stage. The mission on the International Space Station (ISS) was activated in Spring 2009. This project, led by Pascale Ehrenfreund, will be completed in Spring 2011. EXPOSE-R is intended to study the effects of exposure of polycyclic aromatic hydrocarbons (PAHs) to solar UV. The NASA (Organism/Organic Exposure to Orbital Stresses) satellite mission is scheduled to launch in Fall 2010. WARC Co-I Pascale Ehrenfreund worked on development of a UV-Visible spectrometer for the mission, which is intended for in situ analysis of organic materials in future low-orbit satellites and lunar surface exposure facilities. WARC was also involved in instrumentation development that is intended for use on missions that are in the planning stages, including . The miniature mass spectrometer (MMS) that is being developed under WARC at JPL (Mahadeva Sinha and Brian Beard) is designed for a Mars rover-based mission. An anticipated use of the MMS includes pre-screening of samples intended for sample return, including elemental and isotopic analysis, as well as geochronology. Because the quantity of samples that may be returned from Mars is extremely small, in situ pre-screening is important for ensuring that the most promising samples are returned to Earth for detailed study.
List of Project Reports for Wisconsin NAI Team – Year 3 Annual Report
1. Organic compounds
1a. Stability of polycyclic aromatic hydrocarbons and fullerenes in space environment
1b. Proto-cell membrane evolution may have been directed by mineral surface properties
1c. Extra-cellular polymeric substances as armor against cell membrane rupture on mineral surfaces
1d. Dolomite precipitation from solutions containing agar or carboxymethyl cellulose, synthetic analogs for extracellular polymeric substances (EPS)
2. Chemical and mineralogical biosignatures
2a. Chemolithotrophic microbial oxidation of basalt glass
2b. Production of mixed cation carbonates in abiologic and biologic systems
2c. Computational studies of calcium mineralization (calcium phosphate nucleation and dolomite formation) as model systems for biomineral signatures on Earth and other solid planetary bodies
2d. Tectonic hydrogen production through piezoelectrochemical effect, a new mechanism for the direct conversion of mechanical energy to chemical energy by deforming piezoelectric minerals in water
3. Isotopic biosignatures
3a. Quantifying the amount of free oxygen in the Neoarchean photic zone through combined Fe and Mo isotopes
3b. Do iron-rich carbonates from banded iron formations record ancient seawater?
3c. Iron isotope biosignatures: Laboratory studies and modern environments
3d. Stable isotope and mineralogical studies of Banded Iron Formations: O & Si isotopes by SIMS
3e. In Situ Sulfur isotope studies in Archean-Proterozoic Sulfides
4. New frontiers in analytical methods
4a. Improving accuracy of in situ stable isotope analysis by SIMS
4b. Development of Laser Ablation-Miniature Mass Spectrometer (LA-MMS) for geochronology and geochemistry of Martian Rocks
5. Focus on Mars
5a. Astrobiology studies at the Utah Mars Desert Research Station in support of current and future Mars missions
5b. Detection of biosignatures in extreme environments, analogs for Mars
5c. Fluid-mineral fractionation of Mg isotopes and tracing the origin of sulfate minerals
5d. The rock that started it all: Geochronology of Mars meteorite ALH84001
6. Education and public outreach (EPO)
6a. EPO: Astrobiology formal and informal education through NASA/JPL volunteer programs
6b. EPO: Astrobiology Night at the Ballpark
6c. EPO: Elementary School Science Nights
6d. EPO: Imagine Mars training for UW Center for Biology Education ARMS Program
6e. EPO: Imagine Mars at Emerson Elementary Afterschool Program