Abstracts of Posters Presented at Issol '02, Oaxaca, Mexico, June 30 to July 5, 2002

ABSTRACTS OF POSTERS PRESENTED AT ISSOL ’02 OAXACA, MEXICO, JUNE 30 TO JULY 5, 2002 Origins of Life and Evolution of the Biosphere 32: 405–546, 2002. © 2003 Kluwer Academic Publishers. Printed in the Netherlands. 406 ABSTRACTS OF POSTERS PRESENTED AT ISSOL ’02 ABSTRACTS OF POSTERS PRESENTED AT ISSOL ’02 407 PREBIOTIC ENVIRONMENTS 408 ABSTRACTS OF POSTERS PRESENTED AT ISSOL ’02 ATMOSPHERIC NITROGEN FIXATION RATE BY LIGHTNING AND CORONAE DISCHARGES OVER THE EARTH’S GEOLOGIC HISTORY Na Mvondo D.1,2, Navarro-González R.1, Raulin F.2,CollP.2,andMcKayC.P.3 1 Laboratorio de Química de Plasmas y Estudios Planetarios, Instituto de Ciencias Nucleares, Universidad Autónoma de México, Circuito Exterior, Ciudad Universitaria, Apartado Postal 70- 543, México D.F. 04510, Mexico; 2 Laboratoire Interuniversitaire des Systèmes Atmosphériques, Universités Paris 12 et 7 & CNRS, 61 av. Général de Gaulle, F-94010 Créteil Cedex, France; 3 Space Science Division, NASA-Ames Research Center, Moffett Field, CA 94035-1000, USA The production of reactive nitrogen species in the troposphere by lightning and coronae discharges is the only natural source of fixed nitrogen to the biosphere today. In the early Earth, abiotic nitrogen fixation was a fundamental prerequisite for the origin and sustainability of life until the advent of biological nitrogen fixation. Reactive nitrogen could have been delivered to the early Earth by exogenous contributions or fixed by endogenous sources. It is predicted that the endogenous sources dominated the supply of nitrogenated compounds. Among these sources, electrical discharges during thunderstorm could have been an important source of reactive nitrogen (NO, NO2,andN2O) in the terrestrial troposphere. Here we report the first experimental study of the variation of the atmospheric nitrogen fixation rate by cloud-to-ground lightning and by point discharges in the ground over the whole Earth’s geologic history. The energy yields of nitric oxide, nitrous oxide and nitrogen dioxide were estimated over a wide range of atmospheric compositions, from neutral (CO2 –N2) to oxidized conditions (O2 –N2).In the absence of free oxygen, NO was identified as the sole N-product formed during lightning whereas during coronae processes N2O was produced as a secondary product. In the presence of molecular oxygen, among the nitrogen oxides produced NO2 was the predominant form. ORIGINS OF UV-RADIATION SCREENING COMPOUNDS Bettina Heinz Palomar College, 1140 W. Mission Road, San Marcos, CA 92069 California State University San Marcos, Twin Oaks Valley Road, San Marcos, CA 92069 Present life depends on various ultra-violet radiation products for protection against genetic and other damage. such as mycosporine like amino acids (MAA’s) mela- noids, caroteinoids etc. The same protection would be required for early life forms, if not more. Pteridines have been produced by thermolysis and pyrolysis of dry amino acid mixtures (Heinz et al.) as a possible prebiotic pathway. Related compounds such as flavins and acridines were also found in the reaction mixtures. The latter serve as photoactive compounds for electron transfer reactions as well as intercalating agents. However, the UV spectra of the distillates produced by the thermolysis reactions, have strong resemblance to the ones produced by micro-sporine like amino acid UV protectors. This means that amino acids are capable of forming ABSTRACTS OF POSTERS PRESENTED AT ISSOL ’02 409 protective agents against ionizing radiation, which can be damaging to the fragile beginnings of life. METEORITIC IRON-NICKEL AS A SOURCE OF CHEMICAL REDU- CING POTENTIAL AND HETEROGENEOUS CATALYSIS, BOTH WA- TER GAS SHIFT TYPE (WGST) AND FISCHER-TROPSCH TYPE (FTT), ON AN OXIDIZED/OXIDIZING EARLY EARTH S.N. Platts Cogswell Laboratory, R.P.I., Troy NY 12180-3590 U.S.A. ([email protected]) If the auto-generated condition of the late Hadean atmosphere was oxidized and essentially redox neutral (i.e.CO2;N2;H2O), prebiotic chemistry faces a fundamental redox problem: amino acids, lipids, sugars, purines and pyrimidines are all very reduced relative to carbon dioxide. The impact delivery (comets/meteorites) of exogenously-produced organics constitutes one suggested solution to the problem, and hydrothermal vent geochemistry offers another viable scenario for the accumulation of reduced organic species via FTT reactions at mineral surfaces. The present work proposes a third contribution toward the production of reduced organics in situ on the early Earth: that the delivery of large cumulative tonnages of meteoritic Fe-Ni metal to the surface would have constituted a significant reservoir of electrochemical reducing potential towards the redox conversion of CO2 (under aqueous conditions) as the metal was effectively being redox titrated against the atmosphere. Local to the wet surface of a metallic meteoritic body under an (0) oxidized atmosphere, the oxidation of Fe by H2CO3 generates hydrogen in the Fe-Ni/CO2/H2O system which could thus access WGST chemistry (e.g.CO2 + 2H(ads) =CO+H2O). The Ni atoms would be cathodically protected by the prefer- ential corrosion of Fe, hence nickel is expected to be redox stable while it remains electrically connected to any uncorroded iron. Nickel would thus be made avail- + + − → able to serve both as a locus for hydrogen ion discharge (H(aq) e H(ads)) and as a site for the chemisorption of CO towards the heterogeneous catalysis of FTT chemistry, and hence the generation of a suite of reduced and functionalized organic compounds. LIQUID OR SUPERCRITICAL CO2 PHASE ON EARLY EARTH AS POS- SIBLE PREBIOTIC MEDIUM Gyula Pályi and Claudia Zucchi Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, I-41100 MOD- ENA, Italy (e-mail: [email protected]) Model experiments exploring the possibilities of the formation of “biomolecules” under conditions supposed for the early Earth were exceptionally successful in the 20th century [1]. Some gaps, in the chain of molecular events leading from inan- 410 ABSTRACTS OF POSTERS PRESENTED AT ISSOL ’02 imate to animate matter are, however, not yet filled. One of these is the problem of spontaneous polycondensation (water-releasing) reactions in the presence of high excess of water (as primary requirement of life) [2]. A possible solution of this problem would be the consideration of non-aqueous media on the “primitive” Earth. Palaeoclimatological considerations [3] permit the hypothesis that liquid or even supercritical CO2 phases could have locally existed on the early Earth, providing an excellent, non-aqueous medium [4] for prebiotic reactions. Supposed physical and chemical parameters on early Earth and phase behavior of CO2 are compared in this paper, concluding, that – at least in some regions of Earth – liquid or even supercritical CO2 phase(s) might have existed. Experimental verification of this hypothesis is in course. References (a) W. Löb, Ber. Deutsch. Chem. Ges. 1913, 46, 684-697. (b) O. Baudisch, Angew. Chem. 1913, 26, 612. (c) S.L. Miller, Science, 1953, 117, 528-529. (d) A. Lazcano, S.L. Miller, Cell, 1996, 85, 793–798. J. Maynard Smith, E. Szathmáry, The Major Transitions in Evolution. W.H. Freeman/Spectrum, Oxford, 1995. Chapter 3.8 (a) S. Bengtson, Early Life on Earth, Columbia University Press, New York, 1994. (b) G. Pályi, C. Zucchi, L. Caglioti (Eds.), Fundamentals of Life, Elsevier, Paris, 2002. (ISBN: 2-84299-303-9] P.G. Jessop, W. Leitner, Chemical Synthesis Using Supercritical Fluids, Wiley-VCH, Weinheim, 1999. ABSTRACTS OF POSTERS PRESENTED AT ISSOL ’02 411 CHEMICAL EVOLUTION 412 ABSTRACTS OF POSTERS PRESENTED AT ISSOL ’02 BILATERAL SURFACE ACTIVE MINERALS AS SELECTIVE CONCEN- TRATORS, CATALYSTS, AND CELLS IN PUTATIVE PREBIOTIC REAC- TIONS – DYNAMICS AND ENERGETICS Gustaf Arrhenius and Siew Ung Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0236, [email protected], [email protected] Expanding sheet structure minerals have proven effective in mediating several cru- cial steps in chemical evolution. They open pathways to five basic problems in prebiotic chemistry. These are: first, to bring necessarily highly dilute potential reactants from dilute solution into reactive state at high concentration (∼10M) in the mineral interlayer. Second; this concentration process is selective – essential polar- and charged species are withdrawn from a presumed pool of potentially interfering molecules. Third; the catalytic properties of these minerals facilitate constructive reactions such as aldol condensation leading to the formation of nucleoside phos- phates including, selectively, ribose-2,4-diphosphate, and to the oligomerization of nucleotides. Fourth; they provide protection against hydrolysis of sensitive species in the interstitial solution contained by the molecular sheets of the minerals. Fifth; this encapsulated solution of charged and polar reactants stands in diffusive contact with the surroundings through the slit-shaped pores provided by the openings at the crystal edges – the mineral with its reactive internal multicomponent solution may function as a first primitive cell. FATE OF PREBIOTIC ADENINE Corey A. Cohn2, Thomas K. Hansson1, Håkan S. Larsson∗, Stephen J. Sowerby∗, Nils G. Holm∗ and Gustaf Arrhenius2 1 Dept. of Geology and Geochemistry, Stockholm University, SE 10-691 Stockholm, Sweden; 2 Scripps Inst. Oceanography, Univ. Calif. San Diego, La Jolla, CA 92093-0236 USA The plausible prebiotically relevant synthesis of nucleic acid bases has been demon- strated

Load more