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2008 Annual Science Report

University of California, Berkeley Reporting  |  JUL 2007 – JUN 2008

Executive Summary

The UC Berkeley-led BioMARS team continues its efforts to integrate information about the coupled hydrologic, geomorphic, and tectonic evolution of Mars and its mineralogical and geochemical composition with geomicrobiological data from Earth analog ecosystems to support the scientific framework for the search for evidence of past or current life on Mars. The project combines a strong field-based research effort coupled with modeling and/or laboratory work utilizing state-of-the-art technologies. This combination of approaches aims to constrain geological habitats on Mars, either past or present, with what we can learn about potential metabolisms for life there based on these Earth-analogs. The ultimate goal of this work is to suggest where and what we might look for to discover life, or its vestigial traces, on Mars.

We have carried out geomorphological studies aimed at investigating processes that potentially have shaped the Martian surface. We discovered that Box Canyon, Idaho, our Mars analog site for seepage erosion, was instead carved by a large paleoflood about 45 thousand years ago. This finding forces us to rethink the importance of groundwater and seepage erosion on Mars because many Martian canyons, thought to be formed from seepage, have the same morphologic traits as Box Canyon. This work was complemented by supporting studies analyzing sediment transport physics, cosmogenic dating, and seepage erosion in Hawaii. In geomorphological work of direct relevance to Mars, we analyzed Mar Global Surveyor (MGS) spacecraft image data to further constrain potential ocean basins on Mars based on stratigraphic and spectroscopic analysis of current Martian sediments and surface features.

Geological studies on Mars using data from MGS have allowed us to test the idea that polar wander has occurred on Mars and calculate its potential magnitude and direction. This work has implications for the internal evolution, past atmospheric pressure, and (through changes in wind regime) the geomorphology of Mars. Other work based on data from the MAG ER instrument on MGS has constrained the period over which the crust of Mars lost its ability to be magnetized.

Continuing the theme of geochemistry and geochronology we investigated natural isotopes of calcium in calcium carbonate deposits in extreme desert soils from the Atacama Desert and Death Valley. These studies indicate fractionation of calcium isotopes are useful indicators of past geochemical conditions in soils from terrestrial Mars analog environments. Studies of calcium isotopes in calcite deposits from deep-sea sediments indicate biotically influenced sediments preserve significantly different isotope signatures compared to abiotically formed calcites. We are in the process of analyzing calcium isotopes from the Martian metorite ALH84001, initial results suggest they may be useful in constraining the age of Mars.

In research targeting Martian atmospheric processes, we have used mass spectrometry to investigate the kinetics of formation of hydrocarbon species more complex than methane. We have shown that as the carbon dioxide mixing ratio in a simulated atmosphere increases relative to methane, particle production at first increases as carbon dioxide increases and then markedly decreases. The implications are that organic aerosols are likely to have been more prevalent on early Earth and Mars than photochemical models have predicted and could have had a significant influence on surface temperatures. This, in turn, would influence the stability of liquid water at the surface and therefore climate and habitability on ancient Mars.

Our geomicrobiological studies have taken us from local wetland iron seeps in Virginia and Alabama, to Yellowstone, to an ultra-acidic mine in California, to hydrothermal vents in the Pacific, and to Lake Tyrrell in Australia. From the Mars perspective, the common theme of this work is the study of microorganisms fueled by iron redox metabolism.

Our work on the hypersaline Lake Tyrell in Victoria, Australia focuses on iron concretions that may serve as analogs for those which formed at Meridiani Planum on Mars. The potential for the preservation of biosignatures, principally in the form of lipids, makes these 'ferricretes’ especially interesting. Initial studies indicate that lipid preservation is poor under the extreme conditions of the ferricretes in Lake Tyrrell; however other crystalline Fe-oxide phases, such as hematite and goethite better preserve lipid signatures. This work may help constrain the types of minerals on the Martian surface or subsurface that would be the best targets for identification of biosignatures.

In addition to Lake Tyrrell, we have put considerable effort into comparative analysis of several different Fe-dominated natural systems. This work is aimed at understanding their role in biosignature preservation both through mineralogical remains and isotopic signatures. These sites include Fe seeps in Tuscaloosa, AL and Bloomington, IL; a Pliocene-age weathered volcanic tuff unit in Box Canyon, ID; and chemically-precipitated sediments in the Spring Creek Arm of the Keswick Reservoir downstream of the Iron Mountain acid mine drainage site in northern CA. Much of this work is ongoing, but indicates significant microbial influence on both mineralogy of the Fe-oxides and the iron isotopic signals that can be extracted from them..

Work from the acidic, pyrite oxidation-based microbial communities at Iron Mountain, CA have revealed a remarkable a group of ultra-small Archaea. These organisms have only a very small number of ribosomes per cell (ca. 92, compared to ca. 10,000 for E. coli in culture), which are positioned around the inside of the inner membrane. The size and highly organized internal structure of these organisms provide clues to the strategies of life at its lower size limits and how we might go about detecting it, Fig 1.

Investigation of both natural populations and pure cultures of neutrophilic Fe(II)-oxidizing bacteria continue to enhance our understanding of how their physiology and ecology influences the mineralogy and geochemistry that are hallmarks of these organisms in the environment. We have made important progress in delineating Fe(II) oxidation kinetics by these organisms both in situ and in the laboratory. Additional work has focused on the ultrastructure and behavior of a unique stalk-forming Fe-oxidizing bacterium, Mariprofundus ferrooxydans, isolated from a deep-sea hydrothermal vent. This organism bears striking resemblance to micro-fossils as old as 1.7 Ga on Earth. In addition, we have investigated a microbial enrichment capable of anaerobic, nitrate-dependent Fe(II)-oxidation. This relatively complex microbial community appears to work together in carrying out chemolithoautotrophic growth, and can couple growth to oxidation of the insoluble ferrous iron-bearing phyllosilicate mineral biotite, Fig 2.

Related in situ geochemical research on microbially-driven Fe(II) oxidation has been conducted in areas where free sulfide is not present (creeks in VA and Chocolate Pots, Yellowstone National Park), as well as locations where free sulfide is present [local Delaware Inland Bays and the hydrothermal vents at Kilo-Moana (20°3’S, 176°8’W), located on the East Lau Spreading Centre (ELSC), in the Lau Basin, SW Pacific Ocean]. Based on these studies, it is now possible to clearly distinguish between various abiotic and biotic mechanisms for Fe(II) oxidation using real time measurements. We also successfully tested a robot equipped with solid state voltammetric electrodes to measure in situ redox chemistry remotely. The robot could be radio controlled and was capable of floating and moving on water, as well as across soft sediments.

An important goal of the BioMARS project is to contribute to an overall improvement in both the teaching and learning of science locally and nationally through development of instructional materials and approaches that emphasize an evidence-based approach to science education. In conjunction with BioMARS scientists, our E/PO team have designed, developed and field-tested instructional materials used in teacher training efforts and creased a multimedia product “The Process of Scientific Investigation: Iron Processing Bacteria” that is directly related to team research on iron-oxidizing bacteria. This program has been field-tested at several school sites including being a center-piece in summer programs at two local universities. This video and related instructional material emphasize interactive experiemental features that allows students to make predictions, engage in discussions regarding predicted outcomes, and test these predictions using real data. These materials illustrate how important investigation design and detection systems are to BioMARS research in particular, and by extension how these two elements are fundamental to all scientific research. We intend to continue pilot testing of a complementary set of Web-based inter-actives that we intend to refine and field-test during the Fall of 2008.