Organic matter biomarker molecules

Due to the complexity of organic matter sources in estuaries and the aforementioned problems associated with making only bulk measurements to constrain them, the application of chemical biomarkers has become widespread in estuarine research (see review, Bianchi and Canuel, 2001). The term biomarker molecule has recently been defined by Meyers (2003, p. 262) as compounds that characterize certain biotic sources and that retain their source information after burial in sediments, even after some alteration. This molecular information is more specific and sensitive than bulk elemental and isotopic techniques in characterizing sources of organic matter, and further allows for identification of multiple sources (Meyers, 1997, 2003). 

Our contribution to this project was to find and characterize these PAHs. In themselves, they could be biomarkers of fossilized organic matter of long ago, or they could have come from some nonliving source, such as metal-catalyzed reactions of organics on hot surfaces. If we could establish these PAHs as indigenous to the meteorite, then they would be the first observation of organic molecules found from Mars. 

Biological marker (biomarker) molecules are compounds that have distinctive biotic sources and that retain their identity after burial in sediments, even after partial alteration. Most biomarkers are lipids, which are hydrocarbons and hydrocarbon-like molecules. Because of their low susceptibility to microbial degradation compared to other types of organic matter, saturated hydrocarbons — those having only carbon-carbon single bonds — can record many aspects of the depositional history of organic matter sources in lake sediments. A number of detailed reviews of the biomarker contents of lake sediments exist (e.g., Barnes Barnes, 1978 Cranwell, 1982 Johns, 1986 Muller, 1987 Meyers Ishiwatari, 1993). 

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