2001 Annual Science Report
NASA Ames Research Center Reporting | JUL 2000 – JUN 2001
Executive Summary — ARC (dm)
The research efforts of the Ames team integrate a variety of disciplines around three scientific themes that address the context for life, the origin and early evolution of life, and the future of life.
Context for life. We investigate both the chemistry and the environments conducive to life’s origin. First, we trace, spectroscopically and chemically, the cosmic evolution of carbon compounds from the interstellar gas and dust to protoplanetary nebulae, planetesimals, and finally onto habitable bodies. Second, we probe the history of abiotically produced molecules of biological significance. Both investigations rely on spectral and chemical studies of realistic, laboratory analogs tightly coupled with quantum chemical calculations followed by astronomical searches.
We investigate the habitability of planets by identifying and quantifying those factors that collectively determine the inner and outer limits of the circumstellar habitable zone. For example, (1) water must have been delivered to the planet; and (2) climatic conditions must allow surface liquid water to persist. Thus we focus on the origin and physical state of water, a study that depends on the sources of the water, the cycling of water and other volatiles between the surface and interior of a planet, and the detailed climate of the planet.
Origin and early evolution of life and its biosignatures. Do all habitable planets in fact become inhabited? We are identifying specific segments of this problem that are amenable to computational and laboratory investigation. We are testing the hypothesis that the most primitive protocells were structures built of evolving components related to those present in contemporary cells, but functioning without genomic control. We are defining simple biomolecular systems that are capable of performing essential cellular functions, and we will determine conditions under which they can work together in a cellular environment.
We are investigating early microbial ecosystems by combining paleohistorical studies with experimental investigation of representative contemporary microbial ecosystems, and with model building. An improved understanding of long-term evolution of our own biosphere and the biogeochemical cycles that influence the environment will help us to assess the prospects for survival of other biospheres and to develop a strategy to find them by interpreting their biosignatures. Such biosignatures will assist our search for a potential martian biosphere, and to recognize possible spectroscopic signatures of an inhabited planet around another star. We are also examining the effects of varying levels of oxygen upon the photochemistry of atmospheric constituents.
Future of life. We investigate the effect of rapid environmental change on ecosystem properties and the potential for survival and biological evolution beyond the planet of origin. We are defining environmental factors that drive ecological change in South America. We also analyze preserved records of past change ultimately to predict future trends. We are exploring the effects of various forms of radiation upon the survival of life in extreme environments, including space. Our work includes developing methods for assessing radiation damage, examining specific biota for radiation resistance, and exposure experiments that include space flight.
Training, Education, and Public Outreach. Our approach involves several elements. Source material is developed through a partnership between our scientists and participants in the professional training and development programs. This material is translated into curricula, web site content, public presentations, and other education or public outreach products by professional curriculum developers and communication specialists. Products are distributed to selected target groups (i.e., students, educators, and the public, including underrepresented minorities).
Vesicles assembled spontaneously from molecules formed in an interstellar ice simulation (Dworkin et al  Proc. Nat. Acad. Sci. 98, 815-819.). Similar vesicles perhaps played key roles abiotically and thus have great astrobiological importance. This work garnered extensive positive international media attention (e.g., front page coverage on the Washington Post and The International Herald Tribune; radio interviews on NPR and in Canada, television, etc.).
The photochemically-driven oxidation of policyclic aromatic hydrocarbons (PAHs) in interstellar ices can explain the presence and deuterium enrichment of oxidized aromatics in meteorites. Some of these compounds (such as naphthoquinone) play key roles in the biochemistry of some archaea.
Hydrothermal circulation may occur in the martian regolith and may significantly thin the surface layer on Mars at some locations, due to the upwelling of warm convecting fluids driven solely by background geothermal heating. This study is relevant to understanding the seepage channels discovered by the Mars Global Surveyor spacecraft now in orbit about Mars.
Studies of the first proteins of non-genomic origin suggest that functional proteins are sufficiently common in protein sequence space that they can be discovered by entirely stochastic means, such as presumably operated when proteins were first used by protocells.
The production of adenosine tri-phosphate (ATP) using light as the external source of energy was coupled to an ATP-dependent metabolic reaction. However, the coupling was efficient only under a narrow range of conditions that were favorable for both reactions. This work indicates that one of the main challenges in the origin of life was the integration and coordination of different cellular processes.
A theoretical model indicated that collections of proteins could grow and evolve even in the absence of a genome. This process was markedly accelerated when it was coupled to energy-driven activation of monomers.
Microbial mats produce quantities of hydrogen, carbon monoxide and methane that indicate a potentially important role for archean photosynthetic microbial mats in shaping both the composition and oxidation state of the ancient atmosphere.
Microbial biofilms influence the accretion, lamination and early lithification of carbonate stromatolites. These processes can collectively create biosignatures for the microbial mat ecosystem.
An extensive review article addressing extremophiles was published in Nature magazine. (Rothschild, L.J. & R.L. Mancinelli  Life in extreme environments. Nature [London] 409: 1092-1101)