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Project Progress

Peter Backus, Jill Tarter, Rocco Mancinelli- The results of a two and a half day workshop on the topic of the Habitability of Planets Orbiting M Stars was published recently. Thirty scientists from nineteen institutions in the US and UK participated. Thirteen of the participants were from six other NAI Teams. Results of the workshop are reported in a paper published in a special issue of the journal Astrobiology earlier this year. The paper was written over many months through the use of email lists and a secure private web site. Another web site, http://mstars.seti.org provided information for the general public. The paper concluded that M dwarf stars might indeed host habitable planets and identified research topics that would help clarify the issues. Since the workshop, participants have published more than a dozen relevant papers. We had planned to have a second workshop this year to review and discuss progress, but it was canceled due to funding cuts. We are, however, reviewing the literature and will write a final paper as an update to the published paper next year based on our literature review.

Max Bernstein- We have been performing lab measurements to enable the detection of molecular signs of life and discriminate between true and false biomarkers. We have measured IR spectra and photochemistry of aromatic nitrogen heterocycles, the class of compounds that include nucleobases, under conditions found on icy outer Solar System bodies such as Europa. These compounds are good test molecules since they bridge the biotic and planetary domains; they are both fundamental to, and ubiquitous in biochemistry, yet also are present in meteorites, and asteroidal and cometary dust. We found that radiation can cause changes that may make it more difficult to distinguish a biomolecule from abiotic organics.

Janice Bishop & Lynn Rothschild- This year we published a paper in the International Journal of Astrobiology that describes the results of our lab experiments with nanophase iron oxide-bearing minerals as potential sunscreening agents for photosynthetic organisms. Transmittance spectra are shown in Figure 4 of Euglena grown in a suspension of ferrihydrite-schwertmannite-montmorillonite. The chlorophyll absorption at 674 nm decreases with exposure in days and then greatly increases again after resuscitating the Euglena in a visible-light incubator. The normalized chlorophyll band is plotted in Figure 5 for three mineral suspensions and water, and shows an increase in chlorophyll for the ferrihydrite-montmorillonite suspensions indicating that the Euglena grown in the presence of these nanophase Fe minerals are more resistant to solar UV damage. Concurrent with other projects, we are evaluating the spectral properties of Fe-bearing Mars analog sites on Earth and analyzing spectra of Mars for Fe oxide-bearing components. We have collected some material from Yellowstone National Park (YNP) and Bolivia that are currently under study. Spectra of materials from many of these sites (Figure 6) show the presence of nanophase iron oxides/oxyhydroxides that may be facilitating growth of photosynthetic organisms in these natural environments by providing protection from UV radiation. An image of the YNP Chocolate Pots site is shown in Figure 7. Based on the spectral properties of iron oxides and the results of experiments with two photosynthetic organisms, we propose a scenario where photosynthesis, and ultimately the oxygenation of the atmosphere, depended on the protection of early microbes by nanophase ferric oxides/oxyhydroxides. Such niches may have also existed on Mars.
We have been evaluating the Pancam multispectral visible/near-infrared (VNIR) images of Mars from Gusev crater, Mars Express/OMEGA hyperspectral VNIR images and MRO/CRISM hyperspectral VNIR images of Mars in an effort to characterize deposits of nanophase ferric oxide-bearing minerals that could provide UV protected niches for photosynthetic microbes if they were present on Mars. There are a few sites that have been revealed in Gusev crater that show elevated S levels and are brighter than surrounding areas. It appears that this bright salty material is in a layer below the surface dust in a few regions near the Columbia Hills. Spectral analyses of this material indicate the presence of ferric sulfate minerals (Lane et al., 2006,2007; Parente et al., 2007). These unique bright salty patches exposed by the rover wheels in a few locations could represent locations where ferric minerals have provided a UV protected niche for photosynthetic organisms. Analyses of the OMEGA data showed the presence of sulfate minerals in association with hydrated minerals (Bishop et al., 2006). We are investigating these sites further with CRISM data in order to characterize the phyllosilicate and sulfate minerals present and identify ferric oxide/oxyhydroxide minerals accompanying them (Bishop et al., 2007a,b,c). Mapping ferric oxide/oxyhydroxide/sulfate minerals and phyllosilicates on Mars leads us to sites where water was present at one time. Understanding where ferric-bearing components were present in these aqueous environments further helps identify potential UV protected niches.

Nathalie Cabrol- The High-Lakes Project (HLP) completed successfully all ascents and scientific activities planned for the 2006 expedition, which took place October 28—November 26, 2006. The general public could follow the expedition daily on http://highlakes.seti.org. The samples of zooplankton from Licancabur and Laguna Blanca are currently being analyzed (e.g., taxonomy, molecular analyses) by experts in the US, Canada, Australia, Russia, Brazil, and Belgium. Several species are still unidentified as of now. Microbial organisms are being analyzed in the US and Chile and preliminary results suggest a high percentage of unknown organisms at the genus or phylum level. One article was published this year as a chapter of a book at the Cambridge University Press; a second is under review; and a third one has been submitted to the same editor. Two abstracts were selected as oral presentation in professional conferences. We are currently preparing a special issue with the Journal of Geophysical Research. The special issue will consist of 12 articles focused on the results of HLP, and 6 invited papers from other studies by experts on high-altitude lakes.

Chris Chyba, Cynthia Phillips, Kevin Hand- The project has two components. The first, an overview of the astrobiological potential of various geological features on Europa, is proceeding well — we are continuing the study of various proposed formation mechanisms for different feature types such as ridges, bands, and chaotic terrain. The second, a search for current geological activity by comparing Galileo images taken on different orbits, is also in progress. We have completed a first-stage search of the Galileo Europa images to find overlapping images, and are continuing to work on improving our automated search method to make sure that we find all possible comparison images. We have processed a number of comparison pairs, and are currently working on automated techniques for speeding up the comparison process.

We also received funding from the NAI DDF to include 4 extra students in our NSF-funded REU summer program that brings undergraduate students from around the country to the SETI Institute to do research in astrobiology (Figure 8). The four students received a stipend, travel, and housing for the summer. The students were selected in a competitive process from a pool of over 100 applicants. The selected students were: 1) Elizabeth Frank, from RPI, who worked with Jean Chiar at the SETI Institute on a project relating to chemistry of interstellar materials that might be important in the origin of life, 2) Amanda Smith, from University of Virginia, worked with Hector D’Antoni and Jay Skiles of the Ames NAI team, on a project related to paleoclimatology and early Earth conditions relevant to the origin of life, 3) Andrew Honma, from University of Hawaii, worked with Janice Bishop at the SETI Institute on a project relating to spectroscopy of materials on the surface of Mars with potential for aqueous alteration, 4) Teresa Cadarette, of Scripps, worked with Scott Sandford and Rachel Mastrapa of the Ames NAI team, on a project doing laboratory experiments with interstellar ice materials important for prebiotic organic chemistry. The students all will present a talk at the end of the summer summarizing their research, to which members of the SETI Institute and Ames NAI teams, and NAI Central, will be invited. The DDF funding also helped support Cynthia Phillips who ran the program.

Friedemann Freund & Lynn Rothschild- The major objective of this task is to study the causes for the slow but inextricable oxidation of the Earth over the first 3 Gyr of its history. Contrary to the widely held belief that planet Earth became oxidized due to the activity of early photosynthetic microorganisms, we have shown that there is an alternative, entirely abiogenic pathway toward global oxidation: the presence of oxygen anions in the minerals of common igneous rocks that have converted from a valence of 2— to a valence of 1— (peroxy). Upon weathering this peroxy fraction hydrolyzes to hydrogen peroxide, which in turn oxidizes reduced transition metal cations, foremost ferrous iron to ferric iron. This is expected to lead to the precipitation of ferric oxides and, hence, to the deposition of Banded Iron Formations (BIF) in the ocean. After a sufficiently long time, 1-2 billion years, the continental rocks will evolve toward andesitic-granitic compositions, releasing less ferrous iron during weathering, and free oxygen will begin to be injected into the atmosphere. The presence of oxygen in the valence 1—, in the form of peroxy, has yet another important consequence: Upon stressing the rocks, the peroxy bonds break up and generate mobile electronic charge carriers, defect electrons, also known as positive holes or pholes for short. The pholes have the unusual capacity that they can flow out of the stressed rock volume, generating electric currents that can reach or exceed 100,000 amperes, if the stressed rock volume is a cubic kilometer in size. We have shown that this electric current flowing through rocks converts quantitatively into hydrogen peroxide, H₂O₂, at the rock-water interface. This discovery opens the door to re-assess the conditions that primitive microorganisms, which lived in contact with rock surfaces, must have encountered on the early Earth.

Rocco Mancinelli & Amos Banin- We tested soil samples, from the Yungay region of Atacama desert, for toxicity against a variety of microbes ranging from pure cultures obtained from the ATCC to isolates obtained from soil just outside the laboratory. The results indicate that the Atacama soil is not toxic. We also tested Atacama soil for its ability to reduce nitrate to nitrite, the first step in denitrification. These tests were negative. Additionally, we mixed Atacama soil with pure and mixed cultures of denitrifiers to determine if the soil inhibited denitrification in known denitrifiers. These tests have not yet been concluded. These data combined with past data indicate no detection of nitrogen cycling in the field, even under wet conditions. The nitrite reductase gene analyzed for DNA encoding for the key denitrification enzyme suggests that either there are no organisms capable of N-cycling in in the soil, or the soil contains something inhibiting their activity. In a set of soil samples from the Yungay region of the Atacama desert we have conducted detailed analyses of organic and inorganic C and N concentrations. Organic carbon (OC) and organic nitrogen (ON) were low, especially in the soils from the most extreme arid region. The OC/ON ratio was in the range typical for biotically synthesized organic matter. Comparison to estimates of C content in the Mars soil analyzed by the Viking Landers show that the Atacama soils, even in the hard-core extreme desert sites, have very low biological activity as far as terrestrial soils are concerned, but still have higher concentrations of total organic carbon compared to the Mars soils analyzed by the Viking Pyrolytic experiment.

Alessandra Ricca- We are investigating the chemical energetics and plausibility of reaction pathways leading to the formation of nitrogenated aromatics suggestive of purine and pyrimidine bases of RNA and DNA molecules using quantum chemistry. We have focused on the reactivity of pyridine radical cation with acetylene and shown that it is a viable reaction pathway leading to the formation of a bicyclic nitrogenated aromatic molecule. Very recent experiments performed at Virginia Commonwealth University have confirmed our results. In addition, we are investigating the reactivity of N⁺ with various unsaturated hydrocarbons, such as 1,3-butadiene, to form small nitrogenated heterocycles.

Seth Shostak & Molly Bentley- “Are We Alone?” radio show. We have expanded content and improved technical quality of a weekly, one-hour radio program devoted to the topics of astrobiology, SETI, space exploration, and related areas. Whereas most programs of a year ago would have one or two guests, it is now typical to have four, resulting in a greater range of subjects, and snappier interviews. Other show elements, including humorous skits and wider use of music, have been incorporated. In addition, we have invested in hardware and software that has improved both the audio quality and speed and flexibility of production.

Once a month we do a special show on skepticism, taking on such controversial topics as intelligent design and the boundary between religion and science. These are among our most popular shows.

A highly abbreviated listing of guests of the past six months include:

In February, a reorganization at Discovery Communications eliminated their science channel on Sirius Satellite Radio, which broadcast “Are We Alone?” four times a week. We have since begun an effort to secure on-the-air replacement distribution, and are currently uploading shows to the National Public Radio satellite, making the programs available for distribution to the NPR network. However, irrespective of broadcast, the show is clearly enjoying a growing popularity. Internet downloads in the week previous to this report were approximately 50 thousand. Indeed, in 2007, we are expecting that the total number of one-hour shows downloaded will be between one and two million. The show is hosted by P.I. Seth Shostak (SETI Institute) and produced by Molly Bentley, whose efforts are supported by this NAI grant (Figure 9).

David Summers & Bishun Khare- We completed the first experiments to demonstrate abiotic nitrogen fixation this year. Results show that both the theoretically predicted pathway and an alternate pathway can occur and that the observed chemistry is dependent on the amount of water and the state (liquid or gas) in which water is present. We have also discovered this year that NO can alternately be directly reduced to ammonia by FeS minerals in aqueous solution, with good product yield (15-20%). Currently, we are studying pH and other variables for this reaction and are in the process of identifying a gaseous by-product. We are also conducting experiments to determine the most effective method for measuring isotope fractionation. The resulting method will be used as a benchmark for biogenic determination and for identifying the isotopic composition of samples from the Atacama, where nitrates may be of abiotic origin. The results of this work were published in the Journal of Astrobiology.

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