nai

Project Progress

This project involves studies of the deep subseafloor basement biosphere. We are utilizing Ocean Drilling Program borehole (CORK) observatories to access the fluids that circulate through the ocean basin wide environment, where temperatures (2-100°C) and chemistry are conducive to a very broad range of aerobic and anaerobic and heterotrophic and chemolithotrophic metabolisms and survival strategies.

Our current efforts are directed at developing equipment and methods to extract high integrity samples from the boreholes for microbial molecular genetic and metabolic experiments and to collect in situ geochemical data in order to accurately characterize the redox conditions present within the basement environment. We are currently focusing on two independent efforts:

i) Seafloor Instrument Sled for Integrated geochemical and microbial characterization:

We are adapting existing in situ electrochemical voltammetric technology and in situ multi-sample filtration systems to exploit deep-sea ODP borehole observatory’s seafloor fluid delivery systems. The instrument sled, currently nearing field testing, consists of an In Situ Electrochemical (voltammetry) Analyzer (ISEA), a modified McLane Water Transfer System, a central controller/computer, optical and acoustic communication links, battery. The entire system has an open architecture to permit addition of other sensors. The sled fluid intake connects to the observatory’s fluid delivery line via a specially designed manifold. The only surfaces that the basement fluids will contact during sampling is PVDF, a highly inert, chemically and thermally resistant Teflon-like plastic. This new microbiological sampling system provides the exciting capability of making in situ high resolution, real-time, simultaneous measurements of O₂, H₂O₂, HS, S(0), S_x², S₂O₃, S₄O₆, Fe(II), Fe(III), FeS_(aq), Mn(II), and Zn(II) during in situ collection of whole borehole basement fluids or the in situ filtration and fixation or extraction of fluid particles for molecular biology and other studies.

We will field test this system in September, 2005, at IODP borehole observatory 1301A, which is in Cascadia Basin on the flanks of the Juan de Fuca Ridge. Dr. K. Binsted and graduate students Kayo Fujiwara and Brian Norman are collaborating on this project; their role is to develop software to automate the initial processing of the extensive time-series raw data from the in situ electrochemical analyzer.

ii) Downhole Fluid Sampler and Experimental Incubator for Borehole Observatories:

We are currently building a Downhole Sampler (DS) for ocean crustal fluids; subsequent versions of the DS will also permit downhole in situ incubations. Direct collection of fluids at the bottom of the borehole should avoid any potential changes imposed on the fluid composition during its ascent to the surface. Although access for downhole instruments at ODP observatories is intermittent, it is important to verify the integrity of samples collected using our seafloor sampler and observatory fluid delivery line. Using the DS we will study the microbial community structure in the actual context of geochemical and physical conditions of the basement crust. It is our intention to demonstrate the feasibility of collecting uncontaminated fluids from aging, sediment-buried ocean basement crust. We will: 1) Perform preliminary shore-based borehole simulations (underway now); 2) use dissolved, particle and microbial tracers to test the ability of the inlet system to obtain clean samples(underway now); and 3) compare the chemistry, microbial diversity, and community structure of pristine crustal fluids at the bottom of the borehole with those collected throughout the borehole and with seawater in order to establish the nature and magnitude of any influence of the borehole on the ascending fluids (future cruise to a open borehole observatory).

Relevance to Astrobiology: This project focuses on the deep subsurface basement biosphere. Its relevance to Astrobiology lies in the fact that (i) this represents an extreme environment in terms of temperatures (<2 to >100°C), pressure (200 to >500 bar), and fluid flow, and nutrient supply (from abundant inorganic and organic substrates to severely limiting); and ii) this environment represents a valuable proxy for an extraterrestrial rocky body that is at least liquid saturated within its outer crust. This environment is only recently becoming accessible for studies of its biosphere and the projects summarized above are at the leading edge of this exploration.

{{ 1 }}

{{ 2 }}

{{ 3 }}