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Executive Summary

EXECUTIVE SUMMARY

The Evolution of a Habitable Planet

The Penn State Astrobiology Research Center (PSARC) was created in 1998 as part of the NASA Astrobiology Institute (NAI). With a new hire of Jenn Macalady (Assistant Professor of Astrobiology) as part of PSU’s commitment to NAI, PSARC currently is comprised of 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 Macalady, 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, 2004 — June 30, 2005, PSARC has supported all or part of the research/education/PO activities carried out by 80 persons (19 (Co-)PIs, 10 research associates and postdoctoral fellows, 35 graduate students, 8 undergraduate students, 4 technicians, and 4 staff in administration/IT/EPO). In addition, 30 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. More than 100 peer-reviewed papers were published by PSARC members during the period 7/1/04 — 6/30/05.

Research

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 five drill cores from the 2003 ABDP drilling yielded evidence that microbes flourished in the oceans and land, and that the atmosphere-ocean system was O₂-and CO₂-rich, but CH₄-poor, during this period. Determination of an accurate age of a Precambrian paleosol has been difficult, but Capo-Stewart’s group was successful in determining the ages of one of the oldest paleosols at Steep Rock, Canada (3.0 Ga) and of the oldest lateritic (ferric-iron enriched) soils at Hokkalampi, Finland (2.35 Ga) by applying the Nd-Sm and Rb-Sr methods.

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-probe technique. They found an inverse kinetic isotope effect during the photolysis of ³²SO₂ and ³⁴SO₂. From laboratory experiments at 35-150 °C, Schoonen’s group has initiated molecular modeling to evaluate the energetics and kinetics of Fe(II) mediated reduction of dinitrogen and the photochemical reduction of dinitrogen with Fe(II) as the electron donor. In order to estimate the production rate of methane in early Archean Earth, Kasting’s group has conducted coupled ecosystem/atmosphere modeling, which incorporates organisms that utilize H₂, H₂S, and Fe²⁺ as reductants.

III. Investigations of Genomic Record of the Earth’s Early Biosphere. Hedge’s group developed a method for phylogenetic analysis of complete genome sequences, for use with either prokaryotes or eukaryotes. They have also completed an analysis of complete prokaryote genomes and better constrains on the origin of organisms producing metabolic products that influenced the history of the biosphere. House has made significant progress in redefining the Tree of Life by developing a method for building Prokaryotic trees based entirely on Gene Order.

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: (i) the effects of metal limitation (Fe, Mo) on cyanobacteria growth and N₂ fixation; (ii) trace metal acquisition by hydrothermal microorganisms; (iii) barite (BaSO₄) dissolution by sulfate-reducing bacteria; and (iv) the effects of different vitamins on C isotope fractionation during methanogenesis. Ferry’ group has made significant advancement in understanding the structure, function (especially in reduction of oxygen to water), and properties of iron-sulfur flavoproteins (ISF) which constitutes a widespread family of redox-active proteins in anaerobic prokaryotes.

V. Investigations of Modern Analogues of Precambrian Microbial Ecosystems. Kump, Arthur, House, Freeman and their students have initiated 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 been investigating N isotope systematics in anerobic environments and at oxic/anoxic interface using the Black Sea and Fayetteville-Green Lake as Proterozoic analogues. Kump and Arthur published a paper proposing that episodic release of hydrogen sulfide (H₂S) from the ocean caused the end-Permian mass extinction. The discovery by Brenchley’s group of ultra-small microorganisms (< 0.2 micron size) in a 120,000-year-old Greenland-Glacier ice sample has been followed by a series of investigations (phylogenetic and morphological analyses; growth and culturability) to increase understanding their roles in the biosphere on Earth and other planets.

VI. Investigations on Planetary Habitability and Life Detection. Sigurdsson’s group has completed: (1) HST imaging search and data analyses; (ii) followup observations using Gemini, CFHT and NO; (iii) 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 discovered two (or more) stars that may have giant planets around them, one with a ~8 Jupiter mass. Kasting’s group, working in conjunction with Vikki Meadows’ NAI group at Caltech/JPL, have made progress in understanding potential biomarkers on planets around F, G, K, and M stars.

Fieldwork: Geologic field work was conducted in: (a) the Pilbara district, Western Australia by Ohmoto’s group to conduct deep drilling under the Archean Biosphere Drilling Project (5 weeks, July-August, 2004; 3 weeks, June-July, 2005); (b) Arctic Russia by Kump for research on the Archean-Proterozoic transition (July, 2004); and© 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, 2004 — June, 2005).

Education and Public Outreach

Public Outreach: An annual Astrobiology workshop for high school teachers (~10 attendees) was held under the direction of Darren Williams (PSU, Erie) and Jim Kasting during the week of July 25-July 29, 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 2, 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: The Astrobiology Minor Program, established in Fall 2000, as inter-college undergraduate program, has attracted about ten students from the Departments of Geosciences, Astronomy, Microbiology, Biology, and Mathematics. It has been administered by Chris House. An undergraduate summer training program in astrobiology was established at Penn State, with the help of a 3-year NSF REU-Site award (Blair Hedges, PI). Last summer it supported 8 students (sophomores and juniors) from colleges and universities other than PSU to participate in research training under the PSARC PIs for a 10 week period.

Graduate Education: A Dual-Title Ph.D. Degree Program in Astrobiology was inaugurated in August 2004 with a 10-day Astrobiology field trip to southern Canada for ~11 graduate students in this program. Currently, about 10 graduate students are in this program. The dual-title program is under the direction of Lee Kump.