2012 Annual Science Report
University of Wisconsin Reporting | SEP 2011 – AUG 2012
The focus of the WARC Team is on the signatures and environments of life, and in Year 5, the team completed its fundamental research plan, but also significantly expanded its research and Education and Public Outreach (EPO) efforts into new directions. Twenty-two research projects were pursued in Year 5, ten of which extended into areas beyond what was originally envisioned in our proposal. EPO efforts in Year 5 also expanded, and thirteen projects and programs were run through NASA-JPL and the University of Wisconsin. WARC research pursued five themes (topics). First, WARC research on organic compounds included study of the inventories of organics in the terrestrial planets, evolution of organics and their role in the origin of life, the survivability of organics on the planets, and development of early cell membranes. Second, research on experimental studies of biosignatures and paleoenvironmental indicators, a major focus of our proposed research, was pursued in seven programs in Year 5. Third, we applied our knowledge of isotopic biosignatures gained from our experimental program to four research projects on the ancient Earth. Fourth, our work continued on Mars analog environments, which offer an opportunity to test strategies for inferring potential biosignatures on Mars based on terrestrial environments. Fifth, we greatly expanded our work on developing new technologies for astrobiology, beyond what we originally proposed, including new work on in situ laser ablation analysis both in Earth-based labs and planned rover-based instruments, as well as geochronological studies.
Research Topic 1: Organic compounds in the terrestrial planets – Inventories, evolution, survivability, and early life
In Year 5, Nita Sahai’s group pursued three research projects aimed at understanding interaction between lipid membranes and mineral surfaces, development of extracellular polymeric substances (EPS) as a protection against mineral toxicity, and absorption of amino acids on mineral surfaces. Collectively, these studies are aimed at understanding interactions between biomolecules and mineral substrates, a key issue in understanding the origin of life and evolution of cellular membranes. Based on this work, Sahai’s group proposed that mineral toxicity may have been a major driving force in the early evolution of life, where “evolutionary stress” selected only the most robust membranes and vesicles, which in turn probably determined the fundamental nature of cells. Sahai’s team also found that EPS likely developed as a protective measure for early life against the toxic effects of contact with high-charge mineral surfaces. Turning to the theme of organic delivery to the early terrestrial planets, Sahai and coworkers determined amino acid sorption isotherms on a variety of minerals, which will eventually provide a quantitative means for predicting the inventory of organic compounds that may be delivered to a planetary body via meteorite impacts. Work on organic compounds by John Valley’s team focussed on in situ C isotope analysis of subcomponents of ancient microfossils, including preserved cellular walls and putative nuclear (DNA) material. This work demonstrated the potential for in situ C isotope analysis to distinguish eucaryote cellular material from that derived from bacteria or archaea cells, as well as distinction between methanogen/methanotroph and photosynthetic pathways in ancient microbial ecosystems. Pascale Ehrenfreund joined a broad international team in work on the ORGANIC experiment of EXPOSE-R on the International Space Station (ISS), which was returned to Earth for analysis in the lab last year. In-progress analyses of the polycyclic aromatic hydrocarbons and fullerenes that were exposed for >2500 hours on the ISS will provide critical data for the effects of long-term space exposure on organic compounds.
Research Topic 2: Experimental studies of biosignatures and paleoenvironmental indicators
An extensive experimental program was pursued in Year 5, capping our five-year research program in developing new biosignatures. The occurrence of carbonates on Earth and Mars has focussed much of our experimental work on Ca-Mg-Fe carbonates, with a special emphasis on the role of Mg because the high dehydration energies of Mg has previously posed significant experimental difficulties. In Year 5, Chris Romanek’s group demonstrated that Mg-bearing carbonates can be successfully produced using seed crystals, suggesting that nucleation barriers to Mg carbonate precipitation may be overcome in the presence of pre-existing nuclei. In addition, Romanek’s team explored Fe carbonates in the system calcite-siderite, which was an important system on the early Earth, when Fe(II) was abundant in the oceans. Huifang Xu pursued three carbonate studies in Year 5, all focused on the classic “dolomite problem”, a term used to describe the difficulty of producing dolomite in experiment despite its ubiquity in many natural systems. Xu’s team demonstrated that the presence of EPS can promote dolomite formation via hydrogen bonding, providing a link to proposed roles of organisms for dolomite formation. In addition, Xu and coworkers showed that hydrogen sulfide can also promote dolomite formation via enhanced Mg dehydration from solution, providing a positive test of proposed roles for microbial sulfate-reducing bacteria in carbonate formation. Xu tested the results obtained in laboratory experiments using a natural hyper-saline lake system, and he noted that enhanced dolomite formation occurred in the presence of EPS, suggesting EPS catalyzes dolomite formation. Eric Roden’s group continued their work on microbial Fe(II) oxidation of basaltic glass, using organisms that were previously shown to be able to oxidize Fe(II) in clays. Roden’s work has shown that despite the amorphous structure of glass, microbial Fe(II) oxidation of basalt glass was much less efficient than oxidation of Fe(II) in clay minerals. Such results have implications for potential roles of microbial Fe(II) oxidation on early Mars or Earth, and suggest that clay minerals are a more likely site of microbial Fe cycling than basalt.
Research Topic 3: Signatures of life and ancient environments in the early Earth
In Year 5, isotopic studies were pursued on banded iron formations (BIFs), sulfides, and jasper-chert sequences of Paleoarchean to Paleoproterozoic age. John Valley’s team completed an extensive study of O isotope analysis of BIFs of a variety of ages, including detailed study of the very large BIFs of the Pilbara Craton, Australia. They found, via in situ O isotope analysis at the micron scale, that iron oxides had a wide range of O isotope compositions that record a range of diagenetic and metamorphic reactions. Through correlation to petrographic observations, they were able to determine the most primary iron oxide minerals, and demonstrated that these were not in isotopic equilibrium with ancient seawater, but instead recorded diagenetic effects. Continuing the theme of in situ isotopic analysis, Valley’s team also studied S isotope variations in sedimentary sequences that spanned the rise of atmospheric oxygen, and documented an unprecedented range in both mass-dependent and mass-independent S isotope variations on the micron scale, which indicates that multiple S pathways contributed to the isotopic signals. Brian Beard’s team applied in situ Fe isotope analysis to the same BIFs studied by Valley’s group, and these combined results showed that Fe and O isotopes can be decoupled, where O isotopes provide information on the fluid-mineral history of BIFs, whereas Fe isotopes are controlled by processes of Fe oxidation and reduction. Collectively, these studies demonstrate a clear role for microbial processes in BIF genesis, a topic that has been debated for decades. Finally, Clark Johnson’s team completed a study of Paleoarchean jasper and chert deposits from the Pilbara Craton, which previous studies have used to suggest that Fe oxidation occurred very early in Earth’s history via an oxygen-rich atmosphere. By combining Fe isotope analysis with U-Th-Pb geochronology, Johnson’s group showed that oxidation of Fe did indeed occur early, but under oxygen-poor conditions, as demonstrated by low U contents, suggesting the anoxygenic photosynthesis was the likely process of oxidation.
Research Topic 4: Mars, Mars analogs, and other extreme environments
In Year 5, research on Mars analog sites continued via existing projects, and expanded into new sites. Pascale Ehrenfreund and coworkers completed sample collection at the Mars Desert Research Station in Utah, with a focus on detection of clays as a potential repository of organic molecules that would be used in life detection strategies. Max Coleman and his group continued their work at Rio Tinto, with an emphasis on using O isotopes to constrain the pathways that lead to sulfate formation via oxidation of pyrite, and they added new microbiological studies in Year 5. In a new project, Coleman’s team worked on modifying current rover-based wet chemical analysis methods (Robotic Chemical Analysis Laboratory; RCAL), including installation of miniature electrodes for increased selectivity of in situ chemical analysis. Continuing work in evaporite deposits that are Mars analogs, Coleman and coworkers applied H, O, and Cl isotopes to understand the processes by which various evaporite minerals on Mars may have formed, including reconstruction of important parameters such as temperature, humidity, and original water mass. In a new study for Year 5, Eric Roden teamed with the MSU NAI team on studies of iron-bearing springs at Yellowstone. The goal of this new study was to integrate information on microbial metabolisms obtained from genetic studies with chemical and isotopic data to provide a holistic understanding of iron cycling in a hot spring system that was likely analogous to those on Mars.
Research Topic 5: New technologies for astrobiology
In Year 5, WARC researchers continued several projects aimed at developing new analytical approaches for in situ studies on other planetary bodies, and expanded into new directions. Brian Beard and coworkers led a new effort in developing ultra-fast, femtosecond (10-15 s) laser ablation isotopic analysis. This approach promises to be an excellent complement to more traditional methods of in situ analysis such as the ion microprobe. Mahadeva Sinha’s team continued their work on the Miniature Mass Spectrometer (MMS) that is intended for deployment on a rover, turning to new laser ablation approaches for maximizing sampling efficiency for in situ chemical and isotopic analysis. In addition to exploring the effect of laser wavelength on sampling, Sinha and colleagues worked on developing a new ion source for the MMS to address the significant challenges of interplanetary mass spectrometers in terms of sensitivity, accuracy, weight, and power consumption. In addition, Sinha worked on new geochronological applications of the MMS, something not envisioned in the original research plan, but which is critical for constraining the ages of deposits studied by rover-based missions on other planetary bodies. Sinha’s focus has been on developing the K-Ar geochronology system, and in Year 5 he demonstrated that the MMS is capable of producing K-Ar ages via in situ analysis to a precision that is useful for constraining the early history of Mars.
Education and Public Outreach Activities
A wide range of EPO activities were completed in Year 5, from programs that worked with small groups to those that reached millions of people. In Year 5, Kay Ferrari led efforts in the NASA Solar System Ambassadors program, which, in the past year, involved 2,209 Astrobiology-themed events reaching a total of 527,189 people in direct contact events. More people were reached through related media events including 12,236,980 via television, 1,953,540 through radio and 1,698,302 publications. In addition, Ferrari operated the Solar System Educators program, which hosted 27 Astrobiology educator workshops reaching a total of 1220 teachers in the following states: California, Georgia, Hawaii, Idaho, Minnesota, New Jersey, New York, North Carolina, South Carolina, West Virginia, Colorado, Arizona, Oregon, Texas, Michigan and Montana. Other highlights include work by Ferrari and Brooke Norsted on an Astrobiology Boot Camp for Middle School students. Norsted collaborated with Lunar and Planetary Institute personnel to host a two-day workshop for 32 Wisconsin librarians as part of a LPI ROSES grant. In addition, Norsted collaborated with Heather Nelson (Penn State EPO Lead) and Jorge Bueno (Director of the Instituto de Astrobiología Colombia) to co-chair an E/PO session (oral and poster) at the 2012 AbSciCon entitled “Space, Slime, and the Search for Life: Astrobiology Education and Public Outreach”. Norsted worked on the second stage of the biosignatures exhibit in the Geology Museum at UW-Madison, which includes an innovative “smells of the Archean”, which highlights a number of sulfur-based gases for students to try. Finally, WARC Ph.D. student Liz Percak-Dennett was a national finalist in the 2012 FameLab Astrobiology competition.