Extremeophiles and Extreme Environments: January 2008

The NAI is pleased to sponsor travel scholarships for four graduate students (senior level) or postdoctoral fellows (with less than two years of postdoctoral training) to attend the Third International Polar and Alpine Microbiology Conference, to be held in Banff, Alberta, Canada, May 11-15, 2008. See the conference website for more details: Each award will provide up to $2000 to defray the cost of economy airfare from US or Canadian cities and local travel, registration and up to four nights lodging at the workshop venue (shared room, if at all possible). Travel funds will be awarded on a competitive basis.

Astrobiology December 2007, 7(6): 1023-1032

The shallow habitable region of cratonal crust deforms with a strain rate on the order of 1019 s1. This is rapid enough that small seismic events are expected on one-kilometer spatial scales and one-million-year timescales. Rock faulting has the potential to release batches of biological substrate, such as dissolved H2, permitting transient blooms.

Astrobiology December 2007, 7(6): 1006-1022

Europa is a prime target for astrobiology. The presence of a global subsurface liquid water ocean and a composition likely to contain a suite of biogenic elements make it a compelling world in the search for a second origin of life. Critical to these factors, however, may be the availability of energy for biological processes on Europa.

Astrobiology December 2007, 7(6): 987-1005

We examine means for driving hydrothermal activity in extraterrestrial oceans on planets and satellites of less than one Earth mass, with implications for sustaining a low level of biological activity over geological timescales. Assuming ocean planets have olivine-dominated lithospheres, a model for cooling-induced thermal cracking shows how variation in planet size and internal thermal energy may drive variation in the dominant type of hydrothermal system--for example, high or low temperature system or chemically driven system.

Astrobiology December 2007, 7(6): 971-986

Dissolved H2 concentrations up to the mM range and H2 levels up to 9-58% by volume in the free gas phase are reported for groundwaters at sites in the Precambrian shields of Canada and Finland. Along with previously reported dissolved H2 concentrations up to 7.4 mM for groundwaters from the Witwatersrand Basin, South Africa, these findings indicate that deep Precambrian Shield fracture waters contain some of the highest levels of dissolved H2 ever reported and represent a potentially important energy-rich environment for subsurface microbial life. The

Astrobiology December 2007, 7(6): 951-970

Radiolysis of water may provide a continuous flux of an electron donor (molecular hydrogen) to subsurface microbial communities. We assessed the significance of this process in anoxic marine sediments by comparing calculated radiolytic H2 production rates to estimates of net (organic-fueled) respiration at several Ocean Drilling Program (ODP) Leg 201 sites. Radiolytic H2 yield calculations are based on abundances of radioactive elements (uranium, thorium, and potassium), porosity, grain density, and a model of water radiolysis. Net respiration estimates are based on fluxes of dissolved electron acceptors and their products. Comparison of radiolytic H2 yields and respiration at multiple sites suggests that radiolysis gains importance as an electron donor source as net respiration and organic carbon content decrease.

Astrobiology December 2007, 7(6): 933-950

Numerical models are employed to investigate sources of chemical energy for autotrophic microbial metabolism that develop during mixing of oxidized seawater with strongly reduced fluids discharged from ultramafic-hosted hydrothermal systems on the seafloor. Hydrothermal fluids in these systems are highly enriched in H2 and CH4 as a result of alteration of ultramafic rocks (serpentinization) in the subsurface. Based on the availability of chemical energy sources, inferences are made about the likely metabolic diversity, relative abundance, and spatial distribution of microorganisms within ultramafic-hosted systems.

Astrobiology December 2007, 7(6): 905-932

In June 2003, the geochemical composition of geothermal fluids was determined at 9 sites in the Vulcano hydrothermal system, including sediment seeps, geothermal wells, and submarine vents. Compositional data were combined with standard state reaction properties to determine the overall Gibbs free energy (