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2003 Annual Science Report

NASA Jet Propulsion Laboratory Reporting  |  JUL 2002 – JUN 2003

Organic Molecules as Biosignatures

4 Institutions
3 Teams
0 Publications
0 Field Sites
Field Sites

Project Progress

We have continued our investigations into organic biogeochemistry in extreme environments on Earth and the implications for extraterrestrial organic biomarker searches. We are preparing to submit a manuscript describing our analysis of amino acid concentration vs. depth profiles in microbially colonized Antarctic sandstone rocks. We have found an interesting phenomenon in which one or more as yet unidentified molecules containing D-alanine and D-glutamic acid appear to pool at significant depths (up to 10 cm or more) inside the rock, while a second fraction containing D-aspartic acid and D-leucine is concentrated near the surface of the rock, at the level of highest biomass occurrence. These two contrasting profiles may be due to differential breakdown and aqueous transport of peptidoglycans or other biomacromolecules produced by the cryptoendolithic community. This discovery has important implications for the design of spacecraft amino acid analysis instrumentation that might be used to search for similar biological communities on Mars.

We are also extending our database of amino acid and lipid biomarker profiles from low-water-activity environments to include samples of possible Mojave Desert endoliths. These samples include rocks coated with desert varnish, a layer of metal oxides and clays that has been speculated to have a biologically mediated formation mechanism. A USC Geobiology graduate student, Rachel Schelble, is searching for bacterial fatty acid biomarkers in the varnish layers of these samples at JPL under a NASA Planetary Biology Internship.

We have also been investigating possible prebiotic organic chemistry on Titan through the use of laboratory-produced haze analog materials known as tholins. In collaboration with George Cody of the Carnegie Institution NAI team, we have obtained high-resolution 1H, 13C and 15N nuclear magnetic resonance (NMR) spectra of one form of Titan tholin. We are currently in the process of assembling those data into a model chemical structure. This structure will give us greater insight into the chemistry that may occur when atmospheric organic haze particles interact with water, rock, or hydrocarbon phases on the surface of Titan.

    Gene McDonald Gene McDonald
    Project Investigator
    George Cody

    Michael Storrie-Lombardi

    Henry Sun

    Alexandre Tsapin

    Rachel Schelble
    Graduate Student

    Objective 2.1
    Mars exploration

    Objective 2.2
    Outer Solar System exploration

    Objective 5.2
    Co-evolution of microbial communities

    Objective 5.3
    Biochemical adaptation to extreme environments

    Objective 6.1
    Environmental changes and the cycling of elements by the biota, communities, and ecosystems

    Objective 7.1
    Biosignatures to be sought in Solar System materials