Investigation 1

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Research Investigation 1: The inventory of organics in a planetary body – acquisition and modification during biogenic and abiogenic processes

One of the major goals of astrobiology is to determine the chemical and isotopic characteristics of exogenous and/or endogenous organic matter that can be identified on planetary bodies beyond the Earth. Astronomical observations of comets and laboratory measurements of carbonaceous meteorites show a rich carbonaceous inventory. Though several classes of organic compounds important in contemporary biochemistry are found in carbonaceous chondrites, the dominant form of carbonaceous material that has been delivered to the young planets was macromolecular carbon (kerogen-type material). The most common type of organic matter on Earth is kerogen, the insoluble breakdown product of microbial and higher living tissue. The investigation of organic matter in meteorites (as well as early terrestrial kerogens) with respect to their degradation pattern, isotopic fractionation, and inorganic matrix is a key component to life detection on other planets.

Detection of residual organic compounds that might be present from either biotic or abiotic sources, as well as characterization of oxidants in the Martian surface materials, are among the main goals of future Mars missions. Although Viking did not find any traces of impacting organics on the Martian surface, this may reflect environmental alteration, including energetic ultraviolet (UV) radiation, dryness and oxidization. Organic matter, including that delivered from extra-Martian sources, would have suffered from multiple weathering processes not currently understood, including gardening of the surface dust, UV photolysis, and mineral-catalyzed oxidation reactions. Laboratory simulations are a crucial step towards determining the stability and decomposition of specific organic compounds under Mars-like conditions and advance understanding of the chemical pathways by which organic matter is processed on the Martian surface.

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The Murchison meteorite is the best studied object among the carbonaceous meteorites. More than 70 different amino acids, nucleobases, polycyclic aromatic hydrocarbons and many other carbon compounds have been identified in Murchison.

Our objectives in Investigation 1 are to:

  • Understand the chemical composition and isotopic fractionation of extraterrestrial organic matter that may represent the major carbon source for life’s origin on Earth and possibly Mars;
  • Study how we can distinguish between abiogenic and biogenic carbonaceous material in the framework of life detection;
  • Test the survival of organics in simulated planetary environments to determine the most plausible inventory of organics that should be targets of future space missions.

The origin and subsequent modification of organic matter on planetary bodies is the logical first step in the development of biosignatures, because these processes determine the initial compositions and structures that will be subsequently used by life. In the absence of clear morphological evidence for past life such as undisputed fossilized cells, the chemical, molecular, and isotopic composition of organic matter is likely to be one of the strongest lines of evidence for life. Recognizing, however, that modification of organic matter through exposure to extreme conditions is likely on planetary bodies such as Mars, studies of the degradation of organic matter in such environments is critical.

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