what is "serpentinization"?
Serpentinization is the reaction of olivine (a major mantle mineral) with water, producing serpentine minerals. [You may have seen gem quality olivine (peridot) used in art and jewelry.] When the iron in the olivine is oxidized to magnetite, much hydrogen can be produced, fueling microorganisms that use hydrogen for metabolic work. This seems to be a prevalent situation in the deep subsurface of the world's oceans, and is also under study in tectonically uplifted blocks of the ocean floor. The logical place to hike along these uplifted blocks is as close as you can get to a convergent margin, where two of Earth's tectonic plates collide and deep rocks may get plastered to the continent. We head to the Philippines to study just such a setting: mantle rocks have been exposed by tectonics, and we can characterized the geology and biology of these rocks.
what is the "deep biosphere" and how is it related to serpentinization?
Definitions of what constitutes the "deep biosphere" vary, but the general concept is that we are talking about life on Earth in places where sunlight does not reach. This typically refers to, for example, below the ocean seafloor, deep within aquifers on the land surfaces, or even deep inside mine tunnels. You could also consider caves, fluids deep in hot springs, or even deeper soil environments as "deep subsurface." In the last decade, scientists have come to realize that microorganisms living in these sunlight starved environments may have a huge impact on Earth's energy cycles.
Biomass below the Earth’s surface sediments may outnumber the biomass in surface environments, and microbial communities in the deep subsurface are likely adapted to extremes of temperature and pH, and limited carbon, nutrients, and energy sources. Deep biosphere research adds relevance to studies of other “extreme” environments, even in surface ecosystems. Comparison of serpentinization-derived fluids with related surface mixing zone fluids will likely reveal shifts in diversity of taxa and metabolic capacity as a result of geochemical gradients. These terrestrial, high pH, "ophiolite" sourced fluids (very high geogenic methane and measurable electron acceptors) will provide a valuable comparison to other ongoing studies in terrestrial and marine serpentinizing systems. This project will add new context to the discourse on the geobiology of modern serpentinites and may re-define the relevance of serpentinization to life on the Early Earth and astrobiology.
Biomass below the Earth’s surface sediments may outnumber the biomass in surface environments, and microbial communities in the deep subsurface are likely adapted to extremes of temperature and pH, and limited carbon, nutrients, and energy sources. Deep biosphere research adds relevance to studies of other “extreme” environments, even in surface ecosystems. Comparison of serpentinization-derived fluids with related surface mixing zone fluids will likely reveal shifts in diversity of taxa and metabolic capacity as a result of geochemical gradients. These terrestrial, high pH, "ophiolite" sourced fluids (very high geogenic methane and measurable electron acceptors) will provide a valuable comparison to other ongoing studies in terrestrial and marine serpentinizing systems. This project will add new context to the discourse on the geobiology of modern serpentinites and may re-define the relevance of serpentinization to life on the Early Earth and astrobiology.
what are ophiolites?
An ophiolite is a stack of rocks that we find on our continents that originally came from the seafloor! Ophiolites are to be found wherever colliding tectonic places have lodged them over Earth's history. The world map at left (Vaughan and Scarrow, 2004) shows ophiolites painted different colors to show their different ages, as far as we know.
These rocks make it up onto land via a variety of tectonic processes, and represent places to study seafloor environments, chemistry, and geology right here at the surface. Interesting chemistry occurs when water (such as rainwater, groundwater, or seawater) reacts with these rocks, which have high levels of iron in them (see discussion on "sepentinization" above).
Ophiolites are of keen interest to Early Earth geobiology research, because biogeochemical potential produced by the serpentinization of peridotite (i.e., the reaction with water of olivine-rich ultramafic parent rocks), may have important for nurturing life on the Early Earth (Sleep et al., 2004). In addition, it has been found that olivine-bearing mafic rocks similar to those on Earth exist at or below the Martian surface, and are predicted for submarine environments on Europa (Hoefen et al., 2003; McSween et al., 2004), providing close analogue environments to terrestrial serpentinizing systems (Sleep et al., 2004, Schulte et al., 2006). Research into the subsurface habitability of terrestrial serpentine terrains will ground-truth the search for life in ultramafic rock complexes beyond modern Earth. Our project will also supply a continental reference site for other ongoing projects in serpentinizing ecosystems, marine deep biosphere systems, and high pH environments. Mafic/ultramafic units of ophiolites my serve as geological repositories of excess carbon dioxide or radioactive waste materials, locked in carbonate minerals (Arcilla 2011, Milodowski 2009). A clear concept of microbially mediated biogeochemical cycling in ophiolite-hosted fluids is necessary to understand the potential effects of carbon or other waste storage in these settings.
These rocks make it up onto land via a variety of tectonic processes, and represent places to study seafloor environments, chemistry, and geology right here at the surface. Interesting chemistry occurs when water (such as rainwater, groundwater, or seawater) reacts with these rocks, which have high levels of iron in them (see discussion on "sepentinization" above).
Ophiolites are of keen interest to Early Earth geobiology research, because biogeochemical potential produced by the serpentinization of peridotite (i.e., the reaction with water of olivine-rich ultramafic parent rocks), may have important for nurturing life on the Early Earth (Sleep et al., 2004). In addition, it has been found that olivine-bearing mafic rocks similar to those on Earth exist at or below the Martian surface, and are predicted for submarine environments on Europa (Hoefen et al., 2003; McSween et al., 2004), providing close analogue environments to terrestrial serpentinizing systems (Sleep et al., 2004, Schulte et al., 2006). Research into the subsurface habitability of terrestrial serpentine terrains will ground-truth the search for life in ultramafic rock complexes beyond modern Earth. Our project will also supply a continental reference site for other ongoing projects in serpentinizing ecosystems, marine deep biosphere systems, and high pH environments. Mafic/ultramafic units of ophiolites my serve as geological repositories of excess carbon dioxide or radioactive waste materials, locked in carbonate minerals (Arcilla 2011, Milodowski 2009). A clear concept of microbially mediated biogeochemical cycling in ophiolite-hosted fluids is necessary to understand the potential effects of carbon or other waste storage in these settings.