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Inorganic Footprints of Life

Wednesday, April 27, 2011
Douglas (Applicant)

Microorganisms are almost ubiquitous on Earth and in every environment they inhabit, they interact intimately with the geosphere. In environments where water is plentiful, such as lakes, rivers, and oceans, water, by carrying ions and elements leached from soils or dissolved from minerals, the geosphere-biosphere interaction is indirect. However, when water becomes scarcer in more and more arid environments, the effect of life on rock becomes more apparent and of greater consequence to the overall character of the environment. To illustrate this, I will describe how microorganisms use inorganic ions to produce minerals and how this activity affects the character of a geological fabric and can even affect the large scale geomorphology of a landscape. Examples will be given from meromictic carbonate environments, saline-alkaline lakes and, from evaporite deposits (e.g., Death Valley), dry permafrost soils, and the interior of porous rock. Finally, I will describe how knowledge of the microbial effect on rock texture, fabric, and mineralogy may be used to discriminate the past effects of aqueous abiotic from biotic effects and that these effects can be seen and measured by the presently planned payloads of Mars spacecraft. While not providing absolute proof of life’s presence in rock, this approach can be used as a triage for choosing the targets of more definitive measurements.

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