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2008 Annual Science Report

Indiana University, Bloomington Reporting  |  JUL 2007 – JUN 2008

The Diversity of the Original Prebiotic Soup: Re-Analyzing the Original Miller-Urey Spark Discharge Experiments

Project Summary

Recently obtained samples from some of the original Stanley Miller spark discharge experiments have been reanalyzed using High Pressure Liquid Chromatography-Flame Detection and Liquid Chromatography-Flame Detection/Time of Flight-Mass Spectrometry in order to identify lesser constituents that would have been undetectable by analytical techniques 50 years ago. Results show the presence of several isoforms of aminobutyric acid, as well as several serine species, isomers of threonine, isovaline, valine, phenylalanine, ornithine, adipic acid, ethanolamine and other methylated and hydroxylated amino acids. Diversity and yield increased in experiments utilizing an aspirating device to increase the gas flow rates; this could be applied as a simulation of prebiotic chemistry during a volcanic eruption. The variety of products formed in these experiments is significantly greater than previously published and mimic the assortment of compounds detected in Murchison and CM meteorites.

4 Institutions
3 Teams
0 Publications
0 Field Sites
Field Sites

Project Progress

Experiments were carried out to mimic the present Martian diurnal cycling of a Mg-Fe-Ca-Na-SO4 brine derived from acidic weathering of olivine-laden basalt. Experimental brines were laced with an enantiomeric excess of amino acids. Testing was done with and without exposure to the photolytic effects of UV radiation and utilizing a diurnal temperature cycle suitable for simulation of evaporation and sublimation processes in a Martian paleolake or permafrost system.

Results indicate that iron containing brines in the presence of UV are prone to increased levels of amino acid degradation due to photo-Fenton oxidation reactions. In the absence of UV, iron-rich brines provide enhanced preservation, with half lives 200-300% longer than systems lacking iron. Racemization half lives are 30 and 50 times greater than corresponding degradation half lives in iron and non-iron samples, respectively. These initial results provide interesting scenarios in the preservation of organic matter on Mars; an iron-rich subsurface groundwater system, such as those attributed to hematite concretion formation, may provide increased organic matter preservation. Additionally, a limiting factor in life detection may not be the detection of an enantiomeric excess of amino acids but detecting a pool of amino acids at all.

In addition to laboratory brines, we are studying a hydrologically closed basin system in southern California as a Mars analog environment. Samples from a long sediment core (30 meters) drilled at Soda Lake in the Carrizo Plain are being analyzed to determine the yield of enantiomeric excess of amino acids in lacustrine sediments dominated by interbedded clay- and sulfate-mineral assemblages. Obtained values will provide rates of amino acid racemization in environments dominated by seasonal to decadal cycles of evaporation and precipitation of sulfate and chloride minerals.

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    Jeffrey Bada Jeffrey Bada
    Adam Johnson
    Doctoral Student

    Objective 2.1
    Mars exploration

    Objective 3.1
    Sources of prebiotic materials and catalysts

    Objective 3.2
    Origins and evolution of functional biomolecules

    Objective 3.4
    Origins of cellularity and protobiological systems

    Objective 4.1
    Earth's early biosphere

    Objective 4.2
    Foundations of complex life

    Objective 5.1
    Environment-dependent, molecular evolution in microorganisms

    Objective 6.2
    Adaptation and evolution of life beyond Earth

    Objective 7.1
    Biosignatures to be sought in Solar System materials

    Objective 7.2
    Biosignatures to be sought in nearby planetary systems