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2009 Annual Science Report

University of Colorado, Boulder Reporting  |  JUL 2008 – AUG 2009

Executive Summary

1. Catalysis and the emergence of the genetic code (Shelley Copley, lead)

Summary of Recent Progress

Work on the project so far has focused upon the role of catalysis in the emergence of the genetic code (Copley, S. D., Smith, D. E., and Morowitz, H. G. “A Mechanism for the Association of Amino Acids with their Codons and the Origin of the Genetic Code”, Proceedings of the National Academy of Sciences, 2005, 102, 4442-4447) and in the emergence of the RNA World (Copley, S. D., Smith, E. and Morowitz, H. J. “The Origin of the RNA world”, Bioorganic Chemistry, 2007, 35, 430-443). Current work in collaboration with Smith and Morowitz is addressing the emergence of sparseness in metabolism. There are millions of possible small organic molecules, but the core metabolome of the chemolithoautotroph Aquifex aeolicus, which grows on CO2 and H2 and thus synthesizes everything it needs, consists of only about 260 small molecules. A paper on the process by which this sparse network emerged is in preparation. Important factors that we have identified include the nature and complexity of organic inputs, the presence of functional groups that contribute to binding to mineral surfaces and to intramolecular catalysis, and the pruning of complex metabolic networks by various types of catalysts.

Summary of work to be completed in the extension period

Work to be carried out during the no-cost extension will shift to an experimental investigation of catalysis in the RNA World, and specifically to the potential role of peptides as catalytic auxiliaries for RNA molecules. It has been proposed that peptides served as chaperones in the RNA World, providing structural stabilization that allowed RNA molecules to carry out catalytic roles. An additional role for peptides that has not been experimentally investigated may have been provision of an expanded array of functional groups for catalysis. RNA molecules might have provided a scaffold for arrangement of amino acid side chains that actually provided the catalytic power. We will investigate this possibility by using in vitro evolution procedures (SELEX) to evolve RNA molecules that bind to a library of tri-peptides designed to include the functional groups most likely to contribute to catalysis. We will then select RNAs that catalyze a particular reaction (peptide bond formation) in a tri-peptide-dependent manner. Finally, we will determine whether the tripeptide contributes to structural stability or provides catalytic groups for each catalytic RNA-tripeptide combination. This work will be carried out in collaboration with Professor Bruce Eaton (CU-Boulder Dept, of Chemistry and Biochemistry).

2. Major events in the evolution of life (William (Ned) Friedman, lead)

Summary of Recent Progress

We (Ph.D. student Jennifer Winther and I) have characterized the ecological and evolutionary history of fungal symbionts in an unusual but widespread set of plants that spend most of their lives underground. The fungal symbionts throughout the life cycle in ancient land plant lineages (Lycopodiaceae, Psilotales and Ophioglossales) have been identified using DNA sequence data. Based on our DNA sequence data, subterranean phases of the life cycles of ancient land plant lineages obtain fixed carbon through an extensive fungal network that ultimately draws carbon from above-ground photosynthetic organisms in the ecosystem. Additionally, our analyses have identified five new clades of fungi that form associations with subterranean plants. Based on the diversity of fungi that we have identified, it is apparent that multiple species of fungi and multiple species of plants have independently evolved the ability to form plant-fungal associations where the fungus provides the plant with fixed carbon. Our research suggests a new framework for studying the ecology and co-evolution of plant-fungal symbioses where carbon flow between separate plants in a community is potentially widespread through shared fungal networks.

Summary of work to be completed in the extension period

During the coming year, William (Ned) Friedman, in collaboration with Steve Schmidt, will extend work on the flow of organic carbon through plant-fungal symbioses from life underground (mycoheterotrophs) to life at extreme altitudes (extremophiles). Research on life in extreme soil environments has accelerated in recent years, especially in cold, plant-free soils of the high Arctic and in Antarctica. Less well studied are high-elevation soils that can be even harsher than high-latitude soils due to lower atmospheric pressures, higher UV irradiance and drier conditions that occur above 5000 m elevation. High-elevation soils can be more extreme than polar soils because, even during the summer, they experience dramatic freeze-thaw cycles on a daily basis. This temperature variability causes daily freeze-thaw cycles that are often cited as a major disruptor of microbial communities in soil. To date, mycorrhizal fungi have been observed at elevations up to 5250 meters above sea level, but new soils in the region occur up to elevations of over 6000 meters. We will use the DNA amplification techniques developed in the Friedman lab with NASA Astrobiology funding to precisely assess whether the essential components of this critical set of symbiotic associations are present at the extremes of environmental conditions on Earth. This will allow us to document the environmental limits of complex ecosystem carbon flow between eukaryotic organisms.

3. Evolution of martian climate (Brian Toon, lead)

Summary of Recent Progress

This group has been working to complete a model of the Martian climate using the NCAR GCM. We are making good progress on this, and have a running code that we are trying to test. We have also been working on a model for the climate of the early Earth. That model has been used to understand how haze particles might form in the Earth’s atmosphere. We are currently working on a model that reduces solar luminosity to 0.8 of present. Although it runs there are certain current earth aspects we need to remove.

Summary of work to be completed in the extension period

We plan to continue developing the Mars and early Earth models.

4. Late-phase Bondi-Hoyle accretion and a new infrared laser comb for exo-planet searches (John Bally, lead)

Summary of Recent Progress

We are continuing research into the formation and evolution of proto-planetary disks in clustered environments containing massive stars.

In collabration with Dr. Henry Throop ( Southwest Research Institute, Boulder – SWRI), I am completing an investigation of the consequences of Bondi-Hoyle accretion of gas from remnants of the parent molecular cloud onto a disk several million years after the the original condensation of the star and disk.

My collaborators at CU/CASA (Steve Osterman) and NIST (Scott Diddams) have developed an 1.4 to 1.6 micron infrared laser system that produces a comb of wavelength calibration lines at intervals of 12.5 GHz stable to about 1 part in 10^11. We will be combining this new capability with a high resolution IR spectrograph being build by Jian Ge (Univ. of Florida) and deploying it at our 3.5 meter telescope at the Apache Point Observatory. We will be searching for short-period Earth-mass planets around red-dwarf stars and for gas giants around embedded pre-main sequence Solar type stars to constrain when giant planets migrate to become “hot Jupiters”.

Summary of work to be completed in the extension period

Support completion of Bondi-Hoyle accretion modeling and publication of results.

Support observational tests of late-phase Bondi-Hoyle accretion using the VLA and CARMA radio-interferometers and publication of results.

Support deployment of laser-comb wavelength reference at the Apache Point Observatory and the acquisition of “first-light” during early 2010 to demonstrate this new capability.

5. Potential for life on Mars (Bruce Jakosky, lead)

Summary of Recent Progress

Efforts have focused recently on two tasks. The first is examining the availability of geochemical energy that could support metabolism in martian organisms. We have been examining various martian geochemical systems, the types of weathering and redox reactions that could occur there, and the amounts of energy released that could be utilized by organisms. Recent efforts have emphasized environments that are similar to those seen at the martian surface, including the Meridiani region and the Gusev Crater regions that have been explored by the MER rovers. Model development (based on Geochemist’s Workbench) is complete, and preliminary models have been run, showing the amounts of energy available in each environment.

In the second task, Dr. Feng Tian has applied his upper thermosphere-ionosphere model to investigate the responses of early Mars atmosphere to the soft X-ray and EUV (XUV) radiation from the Sun betweeen now and 4.5 Gyrs ago (Tian et al. 2009). In this work they found that even a CO2-dominant early Mars atmosphere would not have been able to survive the strong XUV environment because of the weak planet gravity field. Since January 2009, he has expanded the model to include carbon ion and the relevant chemistry. The expanded model has been validated and largely confirmed the results in Tian et al. 2009. He also collaborated with Jim Kasting at PSU on the development of early Mars photochemical and climate models. They found that although SO2 might have provided extra greenhouse warming for early Mars, the formation of sulfate aerosols could have provided anti-greenhouse effect which could have significantly reduced the net warming contribution of SO2.

Summary of work to be completed in the extension period

On the first task related to geochemical energy availability and habitability, we will complete the running of the models, explore the variation of the input parameters within appropriate bounds, and apply the results to Mars. We will present the results at Mars workshops, including in the forums related to planning upcoming missions (such as MSL (Mars Science Laboratory) landing site planning, and MRR (mid-range rover) and MSR (Mars sample return) mission concept planning. The results will comprise the second half of Lindsey Link Tierney’s doctoral dissertation, and will also be submitted for publication.

On the second task, Feng Tian will focus on two projects. The first one is on the gas exchange between different reserviors (atmosphere, polar ice caps, high latitude highlands, etc.) and its effects on the isotopic ratios of H and O in Mars atmosphere. This work might provide constraints on the possible ranges of the H and O atmospheric isotopic ratios and thus constraints on the evolution of water on Mars. The second project will be on the influence of atmosphere escape on early Mars climate. In addition to finishing the investigation on methane’s climate effect, he and his collaborators will investigate the interactions between the upper and lower atmosphere of early Mars. This will provide more quantitative constraints on the possible O2 concentration and the early water loss mechanisms.

6. Philosophical issues in astrobiology (Carol Cleland, lead)

Summary of Recent Progress

I have been working on two interrelated books this year. Both are under contract with Cambridge University Press and are part of their series on astrobiology. One of them is an anthology (The Nature of Life: Classical and Contemporary Perspectives from Philosophy and Science), co-edited with philosopher Mark Bedau, and the other is an original work (The Quest for a Universal Theory of Life; Searching for life as we don’t know it) authored by myself. The anthology, for which I have written extensive introductions for each of the four sections, has been completed and is currently being processed by CUP.

Summary of work to be completed in the extension period

The other book, for which the anthology functions as a background and source book, will be completed during the no-cost-extension period.