We have examined the chemical and microbiological composition of groundwater Fe seep material from Tuscaloosa, AL and weathered basalt materials from Box Canyon, ID. Significant numbers of both Fe(III)-reducing and Fe(II)-oxidizing microorganisms were detected in both materials, which suggests the potential for microbially-catalyzed Fe redox cycling. Several highly-purified Fe(III)-reducing and Fe(II)-oxidizing cultures have been obtained and are currently being physiologically and phylogenetically characterized. A 16S rRNA gene clone library indicated the presence of a variety of lithotrophic ammonium- and Fe(II)-oxidizing phylotypes in the Fe seep community, and additional clone libraries have been constructed for both the Fe seep and weathered basalt communities. Incubation of amorphous Fe(III) oxide-rich seep material under anaerobic conditions demonstrated the potential for rapid Fe(III) oxide reduction. These results are conceptually consistent with previous studies with cocultures of Fe(III)-reducing and Fe(II)-oxidizing bacteria, and suggest that tight coupling of microbial Fe oxidation and reduction takes place in the seep environment. Similar results were obtained with the weathered basalt materials, which are unique in that they contain magnetic Fe(III) oxide phases (presumably maghemite), which appear to be converted to the magnetite during microbial reduction. The Fe seep and weathered basalt systems provide models for how microbially-catalyzed Fe redox cycling could take place in subsurface Martian environments where reduced fluids/solids contact oxygen-bearing water or water vapor. Simultaneous operation of Fe(III) oxide reduction and Fe(II) oxidation reactions could in principle support a self-sustaining Fe redox cycle-based microbial life system that could be sustainable over geological time scales.

Emerson Lab: Cross Team Collaborations: We have collaborated quite extensively with the NAI team at the Carnegie Institute of Washington, Dr. Sean Solomon, PI. The most exciting aspect of this collaboration is with Dr. Andrew Steele of CIW and Dr. Ed Vincenzi of the Smithsonian Institution. Together we have begun to undertake a detailed analysis of bacterial iron biominerals at very high resolution using Raman Spectroscopy and TOF-SIMS coupled with microscopy to both image and identify mineral states and chemical bonds, qualitatively and quantitatively. This work has yielded some exciting initial results and we are proceeding to do more systematic studies. In addition, we collaborate extensively with Dr. Katrina Edwards who is part of the MBL team on studies at Loihi. We have a separate NSF grant for studying this site with Dr. Edwards and other colleagues.

Luther Lab: Efforts to study in situ Fe(II) oxidation in the microbial mats at Chocolate Pots shows that Fe(II) oxidation is mainly caused by photosynthetic O2 production and 10% or less by chloroflexus, a Fe(II) oxidizing organism. This work was done in collaboration with Dr. Beverley Pierson of the University of Puget Sound, who is a member of the Arizona U. NASA NAI. We have also transfered electrode technology to the U. Hawaii NASA NAI, as one of my former graduate students is now a postdoctoral student there.

The Banfield Lab: In addition to interactions with other NAI teams, the Banfield lab has intiated discussions and meetings with the Spanish and Australian Astrobiology institutes. In the former case, a trip to Spain to investigate paralellisms between the Iron Mountain and Rio Tinto acid mine drainage (iron sulfur biosphere) systems is planned in the near future. In the case of the Australian institute, funds have been secured for reciprocal team visits. An initial field trip to a potential joint field site in Australia (Mars analog site) was undertaken and samples collected for preliminary analysis. We have also participated in discussions with several other teams under the Microbial Systems Initiative.

This project examines relationship between hydrological and biological diversity within a mesophilic, sufide-rich spring system. We are focusing on a set of springs in which the water composition, temperature and discharge are variable because of the mixing of groundwater from different sources. These springs are terrestrial analogues for late-stage groundwater discharge at the Martian surface. The site was chosen chosen based on geologic history, extant biology, and the accretion of large calcite ‘mounds’ created by spring water discharge. The mounds allow us to relate the extant biological communities to that preserved in the calcite mounds and to discern taphonomic processes affecting biosignature preservation. This allows us to identify the potential and challenge of finding a fossil record of life at spring deposits on other planets.

Even though the springs all lie within a few tens of meters of each other there is a wide range of hydrogeochemical properties and this is reflected in the biological communities that inhabit the springs. The dominant biology present at each spring is composed of sulfur-oxidizing members of both the Epsilon- and Gammaproteobacteria as revealed by 16S rRNA analysis; lipid analysis of the biomass confirms this observation. To date wee have been monitoring the hydrology of these springs for two years (discharge, temperature, geochemistry, water source as identified with stable isotopes of O and H). These measurements allow us to develop theoretical models for the hydrogeology associated with the springs and hence to understand their evolution in time, and the origin of spatial variability, of water temperature and geochemistry. We also have biological samples from a year period. In addition to differences between individual springs, we also see seasonal variations in the biological communities at a given spring.

A second site was chosen which we believe may be more analogous to Martian springs during periods of high discharge because the springs originate is largely unweathered basalt. They may also represent a possible terrestrial analog for Fe-based microbial ecosystems on Mars. This site (Box Canyon, Idaho) has been the subject of geomorphological and hydrological research by our NAI team (see subproject 1). We have focused on enumeration, enrichment, and isolation of lithoautotrophic Fe(II)-oxidizing and dissimilatory Fe(III)-reducing microorganisms from this circumneutral pH groundwater seep environment. At present we have several highly-purified enrichment cultures, and are preparing to isolate organisms in pure culture. The phylogenetic position of the pure culture isolates will be compared to in situ microbial community composition at the two sites as determined by 16S rRNA gene clone libraries (currently under construction) in order to assess whether the cultures are representative of dominant Fe redox-metabolism organisms in situ.

Figure (i) Biofilm present on the surface of spring water; (ii) Flourescent in situ hybridization of the biofilm - blue indicates presence of nucleic acids, red and green indicate Epsilon- and Gammaproteobacteria, respectively.

Manga and Dietrich have talked with Nimmo (UCLA) about water-ice-spring interactions.

This project focuses on the early evolution of the Martian atmosphere, the interaction of geodynamic and hydrologic processes, and the possible role of seepage in channel development (with implications for subsurface water available to support life). Our research indicates that organic aerosols may have had a large influence on the climate of early Mars and hence habitability of the planet. Particle formation can occur at considerably lower CH₄-to-CO₂ ratios than predicted by photochemical models. Geophysical modeling of polar wander and internal dynamic processes of Mars has shown that features mapped as potential shorelines, which currently exhibit relief of up to 2 km, could indeed be paleoshorelines from large, vanished oceans. Modeling also suggests that some (or even many) of the Martian outburst floods may have been triggered by large impacts and that the resulting liquefaction provides a source of water and may form the chaotic terrain. In contrast, analysis of some of the landslide features in Valles Marineris indicates that these features were dry fall, rather than associated with water. We conducted field investigations in the Colorado Plateau and Hawaii at sites often cited as examples of seepage driven channel formation. Unexpectedly, we have concluded the case for seepage erosion of bedrock is unpersuasive. Detailed field research at a new site in which a spring headed channel has carved into the basalts of the Snake River Plain has shown subtle evidence that at least one major flood down the plain may be responsible for carving the canyon, rather sapping at the channel head. Key data at this site are exposure age dating of boulders to test whether the channel advanced progressively over 10’s of thousands of years or was essentially in an instant. Our findings here have important implications for the common assumptions about the role of seepage in cutting channels across the Martian surface.