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Project Progress

Morphologic Biomarkers and Microbial Ecology (dm)

The purpose of this project is to study a large variety of terrestrial samples to document the micromorphology of microbial biota, both extant life and fossilized life. The goal is to (1) determine, characterize, and document new biomarkers, and (2) relate microbial types, variations, and related features such as biofilms and mineral precipitates to environment, including acidity, water temperature, water chemistry, and changes in these over hours, days, seasons, years, and geologic time. The application is to provide new potential biomarkers for Mars samples and other astromaterials, and to contribute to our understanding of the effects of environmental parameters on microbial life and their resulting biomarkers. This project considers both extant life and fossilized life.

During the past year we have studied fossil microbes in the Gunflint formation, a complex variety of extant microbes and biofilm forming stromatolite structures in Storr’s Lake in the Bahamas, a variety of biofilms from several locations, and daily and seasonal variations of microbes in a hot spring in Yellowstone. We have found (along with many others) that the Gunflint formation contains abundant evidence for microbes and we are trying to determine whether the various minerals are bioprecipitated, bioassisted, or coincidentally coexistent with microbes. In addition, we have documented possible fossilized microbial structures in the Mars meteorite Nakhla and also in Shergotty. Studies are underway to determine whether these structures are associated with organic compounds, have martian deuterium isotopic ratios, and have carbon isotopic ratios characteristic of martian materials. We found that the hot springs studied in Yellowstone show daily variations in hydrogen peroxide content related to UV solar flux and also to breakdown of hydrogen peroxide by microbial activity. We have also shown significant seasonal and longer term variations of sediments in a Yellowstone hot springs which may be related to different sources of water, water chemistry variation, and the resultant change in the mix of bacteria species.

With our Russian colleagues we have documented possibly the best phosphate microfossils ever found from a deposit of Cambrian phosphorites from Mongolia, and have published a photographic atlas of many of them. Phosphate microfossils are bacteria that are mineralized mainly by Ca-phosphate. They provide an important control for comparison to carbonate-replaced microbes, iron oxide-replaced microbes, or silica-replaced microbes.