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2006 Annual Science Report

Pennsylvania State University Reporting  |  JUL 2005 – JUN 2006

Executive Summary

The Penn State Astrobiology Research Center (PSARC) was created in 1998 as part of the NASA Astrobiology Institute. PSARC currently comprises 19 (Co)-PIs and their research teams from The Pennsylvania State University (Mike Arthur, Sue Brantley, Lisa Brown, Jean Brenchley, Will Castleman, Greg Ferry, Kate Freeman, Blair Hedges, Chris House, Jim Kasting, Lee Kump, Jenn Macaladay, Hiroshi Ohmoto, Mark Patzkowsky, Steinn Sigurdsson, and Alex Wolszczan), The University of Pittsburgh (Rosemary Capo and Brian Stewart), and SUNY Stony Brook (Martin Schoonen). During the period of July 1, 2005 — June 30, 2006, PSARC has supported all or part of the research/education/PO activities carried out by 88 persons (19 (Co)-PIs, 4 research associates, 3 postdoctoral fellows, 37 graduate students, 17 undergraduate students, 4 technicians, and 4 staff in administration/IT/EPO). In addition, 32 Associate Members for Research (who are mostly professors at other institutions) closely collaborate with the 19 (Co)-PIs. Three other Associate Members work closely with the EPO team. About 100 peer-reviewed papers were published by PSARC members during the period 7/1/05 — 6/30/06.


PSARC’s research has focused on critical issues concerning planetary habitability: (1) the evolutionary history of the biosphere, hydrosphere, and atmosphere on Earth and other planets, specifically the times, causes, and consequences of the emergences of major organisms (e.g., cyanobacteria, methanogens, sulfate reducers, fermenters, sulfide oxidizers, and eukaryotes); (2) the effects of photochemical reactions on the early biosphere; and (3) detection of biosignatures on other planets. Our approaches to these critical issues, and some important achievements during the last year, are briefly summarized below:

I. Investigations of the Geochemical Record of the Earth’s Early Biosphere. Ohmoto directed the Archean Biosphere Drilling Project (ABDP), which conducted drilling of two new deep holes during summer 2004 in the Pilbara district, Western Australia to recover modern-weathering-free rock sequences 3.5-2.7 Ga in age. Mineralogical and geochemical investigations of the seven drill cores from the 2003-2004 ABDP drilling yielded evidence that during the 3.5-2.7 Ga period: (1) microbes flourished in the oceans and land; (2) the atmosphere-ocean system was O2-and CO2-rich, but CH4-poor; and (3) mass-independently fractionated sulfur (MIF-S) was absent in most sedimentary rocks. Determination of an accurate age of a Precambrian paleosol has been difficult, but Capo-Stewart’s group was successful in determining the ages of several Archean and Proterozoic paleosols by applying the Nd-Sm and Rb-Sr methods. Kasting’s group has developed new models linking the evolution of climate through geologic time, including: (1) a “thin-ice” model for the Neoproterozoic Snowball Earth; (2) a model linking the MIF-S record of sedimentary rocks, atmospheric O2-CH4 history, and the 2.9 Ga mid Archean glaciation; and (3) a model for the evolution of δ18O of seawater through geologic time.

II. Investigations of Photochemical Reactions of Sulfur and Iron in the Early Earth. To understand the mechanism(s) for the creation of MIF of S isotopes and to aid in the reconstruction of the Precambrian S cycle using the isotope record in rocks, Castleman’s group has been conducting series of laboratory experiments on photochemical reactions of SO2 by utilizing a reflectron time-of-flight mass spectrometer (RETOF-MS) and a femtosecond laser system coupled with the pump-robe technique. They found a pronounced pump wavelength effect on during the photolysis of 32SO2 and 34SO2: an inverse kinetic isotope effect at 197.5 nm, but no reproducible isotope effects at other wavelengths. From laboratory experiments, Watanabe and Ohmoto have recognized the possibility that MIF-S signatures in some Archean sediments may have been caused by diagenetic reactions between sulfate and organic matter. Schoonen’s group has been conducting hydrothermal experiments on reactions between nitrite (or nitrate) and Ni (or Fe) to investigate abiotic formation of ammonium in Hadean hydrothermal systems.

III. Investigations of Genomic Record of the Earth’s Early Biosphere. Hedge’s group completed and released database of published divergence times among organisms. They have also published several papers ranging from deep divergences among animals in the Precambrian to the human-chimpanzee split. Ferry and House have developed a new theory for the early evolution of the cell. The theory is based on the extant pathways for conversion of CO to methane and acetate, largely reduced from the gnomic analysis of the archaeon Methanosarcina acetivorans. It proposes that an energy-conservation pathway was the major force which powered and directed the early evolution of the cell.

IV. Laboratory Microbial Simulations: Astrobiological Signatures. In order to relate the biogeochemical signatures in Precambrian rocks to specific organisms and environments, to understand the response of consortia of organisms to their environment, and to provide the references of biogenic gases in remote sensing of possible life-sustaining planets, our group (House, Arthur, Kump, Freeman, Ferry, Ohmoto and their students) has set up a series of microbial microcosms. Special foci are placed on the chemical and isotopic signatures of inorganic substrates, biogenic gases, and microbial lipids, and on the responses of anaerobes to oxygen and aerobes to methane and sulfide. From separate experiments, House’s group has made significant progress in understanding: (1) the influence of vitamins on the carbon isotope fractionation from inorganic carbon to methane and biomass; and (2) the effect of Fe in N isotopic fractionation by Anabaena. Through a variety of microbes-mineral reaction experiments, Brantley’ group has discovered: (1) the production of a “molybdophore” and extraction of Mo from a silicate by Azotobacter vinelandii; (2) isotopic fractionation of Cu during oxidation of chlacocite by Acidothiobacillus ferrooxidants; (3) the role of cyanobacteria biopolymers n apatite dissolution and P utilization; and (4) the potential for Ni biomarkers by methanogens. Ferry’ group has determined the structure, functions, and properties of iron-sulfur flavoproteins (ISF) and tryptophan repressor binding protein (WreA) which are involved in the oxidative stress response of anaerobic procaryotes from Bacteria and Archaea domains.

V. Investigations of Modern Analogues of Precambrian Microbial Ecosystems. Kump, Arthur, House, Freeman and their students have been conducting a comprehensive geochemical – microbial investigation of Fayetteville Green Lake, New York, a meromictic lake, as a modern analogue of the Proterozoic marine biosphere. Arthur’s group has investigated N isotope systematics in modern anerobic environments and at oxic/anoxic interface using the Black Sea and Fayetteville-Green Lake as Proterozoic analogues. Kump’s group has initiated a project to explore the nature of chemical weathering at the end of the Precambrian, following the “Snowball Earth” glaciation. Kump-Arthur group has submitted several papers on the Permian/Triassic extinction, evaluating their model of the mass extinction by H2S release from carbon and sulfur isotope records. Brenchley’s group has continued investigations (phylogenetic and morphological analyses; growth and culturability) of psychorphillic (cold-loving) microorganisms and their cold-active enzymes to increase understanding their roles in the biosphere on Earth and other planets. Macalady’s group has been investigating microbial communities in caves in Italy, and House’s group investigating microbial communities in deeply buried marine sediments.

VI. Investigations on Planetary Habitability and Life Detection. Sigurdsson’s group has completed: (1) analysis of Hubble Space Telescope observations of white dwarf candidates; (2) Spitzer observations and data analyses. Wolszczan’s group has continued a search for planets around K-giants with the Hobby-Ebbery Telescope (HET). They have collected multiple epoch observations for 80 stars, and discovered several of them may have giant planets around them.

Fieldwork: Geologic field work was conducted in: (a) the Pilbara district, Western Australia by Ohmoto’s group to investigate the geology of the ABDP drilling sites and of 3.4 Ga paleosols (3 weeks, June-July, 2005); and (bm) Fayetteville Green Lake, New York by Kump, Arthur, Freeman, House and their students to investigate the microbial ecology and to collect water and microbial samples for laboratory simulators (July, 2005 — June, 2006).

Education and Public Outreach

Public Outreach: An annual Astrobiology workshop for high school teachers was held under the direction of Darren Williams (PSU, Erie) during the week of July 30-August 4, 2005. Space Day at PSU, an annual one-day event to showcase the exciting space-related research carried out at PSU, was held on April 22, 2005. PSARC faculty and graduate students exhibited posters describing their Astrobiology research and worked with the general public on hands-on experiments to increase the public’s awareness of Astrobiology. In May, 2005, we created an Astrobiology Exhibit, with displays of illustrations, cores, and outcrop samples from the ABDP, in a newly renovated Museum of the College of Earth and Mineral Sciences. This exhibit has already attracted a large number of visitors.

Undergraduate Education: Astrobiology Minor Program, established in Fall 2000, as inter-college undergraduate program, had five students from the Departments of Geosciences, Astronomy, Microbiology, Biology, and Mathematics. It is administered by Jenn Macalady. A total of 17 undergraduate students were involved in a variety of research carried out by the 19 (Co)-PIs.

Graduate Education: A Dual-Title Ph.D. Degree Program in Astrobiology, inaugurated in August 2004, currently has 15 graduate students. Two students, Pushker Kharecha (Astrobiology/Geosciences) and Jaime Blair (Astrobiology/Biology), received Ph.D. degrees in the Summer of 2005. The dual-title program is under the direction of Lee Kump.