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Executive Summary

The Penn State Astrobiology Research Center (PSARC) was created in 1998 as part of the NASA Astrobiology Institute. PSARC is currently comprised of 19 (Co)-PIs and their research teams: Mike Arthur, Sue Brantley, 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 of The Pennsylvania State University; Rosemary Capo and Brian Stewart of The University of Pittsburgh; and Martin Schoonen from SUNY Stony Brook. During the period of July 1, 2007 — June 30, 2008, PSARC has supported all or part of the research/education/PO activities carried out by 93 persons (19 (Co)PIs, 6research associates, 9 postdoctoral fellows, 41 graduate students, 13 undergraduate students, 1 technician, and 4 staff in administration/IT/EPO). The total number of PSARC personnel has remained about the same as last year. In addition, 36 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 70 peer-reviewed papers were published by PSARC members during the period 7/1/07 — 6/30/08.

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’s group continued mineralogical and (bio)geochemical investigations of seven cores from the 2003-2004 ABDP (Archean Biosphere Drilling Project) drilling. They also conducted field investigations (3 weeks in 2007 and 3 months in 2008) of the “probable lateritic paleosols” that developed on the oldest land surface ~3.4 Ga ago in the Pilbara Craton, Western Australia, and laboratory investigations of these samples. These investigations have yielded a variety of data suggesting that by ~3.4 Ga: (1) an extensive biosphere developed on land, as well in the oceans; and (2) the atmosphere-ocean system became O₂-and CO₂-rich, and CH₄-poor.

Stewart-Capo group has determined the Nd-Sm ages (~3.5 Ga) and Rb-Sr ages (2.6 — 2.8 Ga) of the above paleosols in the Pilbara Craton. These data put constraints on the ages of soil formation and a major tectonic event, respectively.
Kump has developed a hypothesis that the rise of atmospheric O₂ around 2.45 Ga ago was a consequence of the establishment of large and thick continents and associated subaerial volcanism. His group also published a paper, suggesting that anoxia and the buildup of hydrogen sulfide were more important than imagined for the end-Permian mass extinction and less important for the Proterozoic than envisioned. They are also continuing geochemical studies of paleosols in South Dakota and Iowa to understand changes in the biosphere during the latest Precambrian — Cambrian period.
Ohmoto and Kump organized a 10-day Field Workshop “Biosignatures in Ancient Rocks” in Ontario, Canada under the sponsorships of the NAI, the Agouron Institute (AGI), the Canadian Institute for Advanced Research (CIFAR), the Ontario Geological Survey, and Laurentian University. This workshop brought together 15 of the world’s leading scientists and ~40 young scientists (professors, research associates, post-doctoral fellows, and advanced graduate students from USA, Canada, England, Denmark, and Japan) to promote research on the biological and chemical evolution of early Earth and Mars.

II. Investigations of Photochemical Reactions of Sulfur and Iron in the Early Earth.
The mass-independently fractionated sulfur isotopes (MIF-S), primarily found in pre-2.4 Ga sedimentary rocks, have been interpreted by many geoscientists as the products of UV photolysis of volcanic SO₂ in an O₂-poor atmosphere. Castleman’s group has been investigating the kinetic isotope effects during 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 that the photolysis of ³²SO₂ and ³⁴SO₂ were strongly affected by pump wavelength (~200 to 197 nm) and power.
Kasting’s group have updated their methane greenhouse model for the early Earth by including the greenhouse effect of ethane and the anti-greenhouse effect of organic haze. They analyzed the MIF-S record to find evidence for the existence of such haze during the mid-Archean, between 3.2 and 2.8 Ga. They have also worked on the problem of hydrogen escape from the early Earth, and on the significance of O and Si isotope records of sedimentary rocks in terms of surface temperatures on early Earth.
Ohmoto’s group has developed a new theory that the MIF-S signatures in some Archean sedimentary rocks were most likely associated with chemisorption of sulfur-bearing compounds on immature organic matter (e.g., kerogen) during reactions with sulfate-rich submarine hydrothermal fluids. Therefore, the MIF-S record represents biological and thermal evolution, rather than atmospheric evolution, of early Earth. This theory was developed from: (1) theoretical studies (i.e, ab initio calculations), published in two papers; (2) analyses of mineralogical and geochemical characteristics of rocks with MIF-S signatures; and (3) laboratory experiments on sulfur isotope effects during thermochemical sulfate reduction by solid amino acids.

III. Investigations of Genomic Record of the Earth’s Early Biosphere.
Hedge’s group continues to update Time Tree (www.timetree.org), which presents divergence times of organisms in ~3,000 publications.

IV. Laboratory Microbial Simulations: Astrobiological Signatures.
Ferry’ group has continued to work on a major question “how anaerobic Archaea cope with oxidative stress, with the long-term view of how anaerobic life evolved to adapt to rising oxygen levels before, during and after the evolution of oxygenic photosynthesis. The research also addresses ancient enzymes involved in metabolic pathways with a focus on energy conservation in methanogenic Archaea.
From a variety of laboratory culture experiments, House’s group has published papers showing that: (1) cyanobacteria have a distinct nitrogen isotopic signature when exposed to high Fe concentrations, a condition that might occur during ocean anoxic events; and (2) methanogens can grow by producing methyl-sulfides.
Brantley’ group has continued to investigate the roles of organisms in chemical transformation of rocks during interactions with water and air. The chemistry of metals and minerals are being probed to elucidate possible biosignatures that may be identified on Earth and Mars. Specifically, they have been investigating: (1) the mechanisms that a variety of microbes use to obtain bioessential metals (e.g., Fe, Mn, Ni, Cu and Mo) from rocks ; (2) how these metals are utilized in microbes; and (3) how the kinetics of biochemical and isotopic reactions involving isotopes of Fe, Mo and Cu differ under different (bio)geochemical conditions.

V. Investigations of Modern Analogues of Precambrian Microbial Ecosystems.
Brantley’s group has investigated basalt and olivine weathering in a Mars analog environment, the Sverrefjell volcano in Svalbard. They have also compiled mineral weathering rates in natural environments and those in laboratory conditions in order to provide the basic kinetic data that are necessary to interpret weathering profiles on Mars to study the planet’s aqueous chemistry.
Macalady’s group has investigated the ecology and evolutionary relationships among extremely acid-loving bacteria and archaea living in biofilms called “snottites” in sulfidic caves in Italy and Mexico. The acid-loving microbes form the base of food chains cut off from the surface, and are interesting from an astrobiological perspective because they are microbially dominated ecosystems (like ecosystems on early earth and potentially elsewhere in the universe). The snottites are also important because they help us learn how life adapts to environmental conditions much different from the ones that can be tolerated by our own species.
A research goal of Brenchley’s group is to discover microorganisms surviving in cold or frozen environments and to use this information to understand how different organisms survive extreme habitats elsewhere in the solar systems. Their recent results demonstrated that abundant populations, including many bacteria representing novel taxa, exist frozen in a Greenland glacier ice core for at least the last 120,000 years. Current isolates are being characterized as new species of ultra-small celled bacteria.
House’s group is also investigating the metagenomic signatures of microbial life in the marine subsurface, and the metagenomics of microbes in the Dead Sea, a possible analogue for Mar’s terminal oceans.

VI. Investigations on Planetary Habitability and Life Detection.
Sigurdsson’s group has completed: (1) A theoretical model of post-migration planet formation; (2) analysis of Sptzer Space Telescope data; and (3) analysis of Hubble Space Telescope data to follow-up observation doing direct imaging search for giant planets around nearby white dwarfs obtained in current cycle.

Fieldwork:
Geologic field work was conducted in: (1) 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, August, 2007; 3 months, May — August, 2008); (2) the Sudbury — Temagami — Cobalt — Timmins — Wawa — Thunder Bay areas, Ontario, Canada as a part of Field Workshop “Biosignatures in Ancient Rocks” (10 days, September, 2007); (3) central Italy sulfide caves by Macalady group for geochemical measurements and sample collection of extremely acidic snottite biofilms for genomic analysis (5 weeks, May-June, 2007).

Education and Public Outreach
Public Outreach: Three five-day astrobiology workshops for high school teachers were held during the summer of 2007:“Evolution” in July, “Planet, Star, or Neither?” in July, and “Origins of the Cosmos” in August, 2007. PSARC faculty and graduate students presented talks and exhibited posters describing their Astrobiology research and worked with the general public on hands-on experiments to increase the public’s awareness of Astrobiology on a number of occasions. An Astrobiology Exhibit, with displays of illustrations, cores, and outcrop samples from the ABDP, created in a newly renovated Museum of the College of Earth and Mineral Sciences in 2005 continued to attract 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 13 undergraduate students were involved in a variety of research carried out by the 19 (Co)-PIs. Over 1,500 students per year are enrolled in the 13 astrobiology-related undergraduate courses.

Graduate Education: A Dual-Title Ph.D. Degree Program in Astrobiology, inaugurated in August 2004, currently has 24 graduate students. During the period between 7/1/07 — 6/31/08, 2 students graduated with Master’s degrees (David Bevacqua and Tazzi Howard) and 11 students with Ph.D. degrees (Matthew Bachmann, Fabia Battisuzzi, Shawn Goldman, Libby Hausrath, Avi Mandell, Karla Panchuk, Tony Ricardi, Sherry Stafford, Alexis Sitchler, Matthew Wander, and Sabrina Zimmerman). The dual-title program is under the direction of Lee Kump.