The East German Creek Mars analogue site in Manitoba consists of hypersaline waters discharging up through a Devonian limestone reef. It appears to be an excellent analogue for putative springs discovered on Mars. Preliminary investigations at the site suggest that the mineralogy at the site varies with distance from the discharge point. To address this issue we will look for any changes in the composition and structure of the minerals the precipitate in the spring discharge waters as a function of distance from the spring. This information will be used to analyse spectroscopic data for presumed spring deposits on Mars, to determine whether similar variations in mineralogy with distance from discharge points occur on Mars.

The Triassic age Lake St. Martin impact crater in Manitoba hosts a thick sequence of presumed intracrater evaporite gypsum deposits that have been exposed by historic quarrying operations. These deposits will be examined to characterize weathering textures, analyse the nature of induration of gypsum sediments, and characterize glacial-gypsum interactions (scour marks, drag folds). The intent is to derive information that can be used in the analysis of imagery and spectroscopic data for gypsum-rich terrains on Mars.

I am assisting Melissa Battler in her research on biomineralization on Axel Heiberg Island.

Biological attributes of Mars analogue sites: East German Creek hypersaline springs and Lake St. Martin crater

The East German Creek Mars analogue site in Manitoba consists of hypersaline waters discharging up through a Devonian limestone reef. It appears to be an excellent analogue for putative springs discovered on Mars. A number of the springs host iron-stained algal mats and other microbiological communities. This project will examine the nature of the algal mats and microbiology at the springs and as a function of distance from the discharge points. This information will be coupled with measurements of water chemistry and determinations of mineral precipitates, in order to unravel biological-geological-water chemistry interactions, and provide guidelines that can be used to search for the remains of similar environments on Mars.

The Triassic age Lake St. Martin impact crater in Manitoba hosts a thick sequence of presumed intracrater evaporite gypsum deposits that have been exposed by historic quarrying operations. These deposits will be examined to search for cryptoendoliths and the presence of microbes encased in the gypsum sequences. This information will be used to develop microbiological search strategies for future Mars missions.

PROJECT COMPLETE

Sulfate reducing bacteria are important actors in the sulfur, carbon, and oxygen cycles. Their highly tuned metabolism produces characteristic isotopic fractionations evident in waste products (e.g., H2S) and in the metabolic substrates they utilize (e.g., SO42-). These sulfur isotopic signatures are then preserved in the rock record (eg., in grains of pyrite) as the fingerprint of microbial activity. They are used today by biogeochemists to infer the environmental characteristics of the early biosphere as well as to identify evidence for early microbial activity. These biogeochemical studies, however, rely on the assumption that the metabolism of sulfate reducers today and in the past has been the same. Experimental evolution can address this question by revealing the rate of change of microbial metabolism under specific stressors and its impact on sulfur isotopic fractionation. In order to experimentally determine the effects of changes in microbial metabolism on isotopic fractionation, it is essential to understand the experimental subject: Desulfuvibrio vulgaris. This sulfate reducer was chosen as guinea pig as it is well-studied and ubiquitous in anoxic environments worldwide.

The primary objective of my research project is to determine how salt (NaCl) acts as a selective pressure on D. vulgaris cultures. In order to achieve this objective we need to be able to quantify the growth characteristics of D. vulgaris as evolution proceeds. This will be performed with a high sensitivity protein assay as well as flow cytometry and quantitative tracking of specific genetic markers inserted in different populations of D. vulgaris. An endeavour of my initiative to this project will be to determine growth characteristics of sulfate reducers by using protein-specific tags to differentiate salt-adapted individuals from non-adapted ones. These tests are all being developed with one goal in mind: the determination of fitness (a measure of the growth of a descendant population compared to its ancestors under identical experimental conditions) with the highest accuracy possible. The fitness experiments must be done in order to demonstrate that a significant change in the metabolism of the bacteria, and thus adaptation to the novel conditions, occurred.

The primary outcome of this research will be a set of descendant populations of D. vulgaris, each grown in media with a different salt concentration as well as estimates of the fitness of those populations compared to their ancestral strain. These populations will be investigated for their characteristic sulfur isotope fractionations, with the goal of producing an isotopic dataset that I can present at the Fall 2010 meeting of the American Geophysical Union.