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Project Progress

Eigenbrode has been developing thermochemolysis methodologies for extracting components of complex organics molecules from samples that pose unique analytical challenges because of their mineral composition. These include iron-oxide rich samples regarded as analogs to ancient aqueous environments on Mars and ancient Earth, as well as perchlorate-laden samples. The challenge in these cases is that the mineral oxidants can both chelate or ionically bond with the organics making them difficult to extract by traditional methods and contribute to partial or complete destruction of organic molecules over time (as in the rock record) or during traditional thermal extraction (in the lab). A manuscript containing current results on the impact of perchlorates and the applicability of the thermochemolysis approach for sediments of extreme chemistry is in preparation. In addition, this study has contributed to new perspectives on the organic (bio)geochemistry expected on Mars – a perspective being written up for a News and Views type article for submission to Geophysical Research.

The above investigations meet NAI objectives (5.1) Environment-dependent, molecular evolution in microorganisms, (5.3) Biochemical adaptation to extreme environments, (6.1) Effects of environmental changes on microbial ecosystems, and (7.1) Biosignatures to be sought in Solar System materials; and may have implications for objectives (2.1) Mars exploration and (4.1) Earth’s early biosphere.

Carbon Isotopic Records of the Neoarchean
In collaboration with colleagues of the NAI MIT (Roger Summons et al.) and Wisconsin (John Valley, Ken Williford, et al.) teams, Eigenbrode is working to understand the spatial and molecular variations in stable carbon isotopes of sedimentary organic matter in the 2.7 to 2.5 Ga sedimentary record of Neoarchean Hamersley Province. This work was stimulated by the Rasmussen et al. Science paper and notable lack of analytical standardization, sample set integrity, and no consideration for alternative (biogeochemical) interpretations. The goal for this project is to assess how microbial inputs having a very broad isotopic range are preserved in the Archean record and if other non-biological components are recognizable. Most of our early work was steered towards developing a set of standards appropriate for Archean kerogens necessary for verifying results from the CAMECA 1280 Ion Microprobe. Preliminary results from three kerogen samples indicate a complex history of isotopic fractionation and organic partitioning. These results will be presented at AGU by Ken Williford et al.

The above studies meet NAI objectives (4.1) Earth’s early biosphere, (5.1) Environment-dependent, molecular evolution in microorganisms, and (5.2) Co-evolution of microbial communities.

Fatty acid composition of glacial ice (substudy of the SLIce project that leverages support from NAI GCA)
As part of the SLIce study previously funded by EXOB and MFR programs, a subset of the filtered particulates of glacial-ice meltwater and associated environmental samples in the glacial environments of Svalbard are being analyzed for fatty acid composition using a automated thermochemolysis GCMS method. These data are being collected by Eigenbrode and Floyd and molecular interpretations are in early stages. The fatt acid results are being merged with other molecular results (amino acids, PAHs, other hydrocarbons, bacterial and eukaryotic biomarkers, bulk lipopolysacchride, bulk in situ adenosine triphosphate, and dissolved molecules) and contextual data for the same samples. This comprehensive molecular biosignature study is the heart of the SLIce investigations and is aimed at distinguishing different organic inputs to ice. SLIce will provide mission guidance for organic studies of extraterrestrial ices.

The above investigations meet NAI objectives (5.1) Environment-dependent, molecular evolution in microorganisms, (5.3) Biochemical adaptation to extreme environments, and (7.1) Biosignatures to be sought in Solar System materials; and may have implications for objectives (2.1) Mars exploration.