SCOL Project: Defining Phosphorus and Nitrogen Speciation as Cool Fluids Circulate Through Iron-Silicate Rocks
A continuum of chemical environments are stably established as cool fluids circulate within iron-bearing silicate rocks in the absence of hydrothermal activity. Several aspects of these subsurface water/rock reaction systems may have been stably conducive to the receipt, reaction, storage and release of organic molecules relevant to prebiotic chemistry on the early Earth and Mars.
This project will focus on the potential availability of reduced and reactive forms of phosphorous (P) and nitrogen (N) formed in the subsurface during low-temperature water/rock interaction, as modulated by the hydration and oxidation of iron silicates and (hydr)oxides, as a key connection point between prebiotic geochemistry and organic chemistry. Specifically, we will address several first-order questions regarding the forms of N and P available in ultramafic rocks hydrating under near-surface conditions. Using materials and chemical information derived from ultramafic rocks and fluids currently reacting hundreds of meters under the surface, we will determine the dominant organic and inorganic forms of P and N potentially produced during extensive water/rock interaction under highly reducing conditions near the stability limit for water. This work will require detailed X-ray spectroscopic and nuclear magnetic resonance spectroscopy to be conducted in collaboration with other SCOL Investigators. Separately, we will conduct a spectrum of experiments focused on the reactivity of a common metastable phase in ultramafic rocks, ferroan brucite (Mg,Fe(OH)2). Using natural and synthesized ferroan brucite, we will constrain the mechanisms controlling the reduction of nitrates and nitrites to ammonium, giving rise to a flux of reduced N. The two projects will be integrated to examine the formation of reduced P, N and PN compounds produced under nonhydrothermal conditions that could give rise to efficient phosphorylation and amination reactions. Exploring the (hydro)geochemical connections that likely existed between surface and subsurface environments on the early Earth should increase our ability to identify the combination of atmospheric and rock-hosted chemical processes that give rise to successful reaction networks for organic syntheses leading to the formation of proteins, nucleic acids, membranes and more.
Alexis Templeton received her Ph.D. in mineral and biological surface chemistry from the Department of Geological Sciences at Stanford University in 2002. Currently a professor of geobiology and geochemistry at the University of Colorado, she has previously held positions at the Lawrence Berkeley National Laboratory and the Scripps Institution of Oceanography. Templeton is the principal investigator of the Rock-Powered Life NASA Astrobiology Institute; she has also received awards and fellowships from the Geochemical Society, the Mineralogical Society of America, the Geological Society of America, the David and Lucile Packard Foundation, the Advanced Photon Source, the Department of Energy and the National Science Foundation.
Her research focuses on mechanistic studies of mineral-fluid and mineral-microbe interactions, using spectroscopic tools to probe the distribution, speciation and reactivity of metals (Fe, Mn) and light elements (S, N, P) at interfaces. She leads a geomicrobiology and low-temperature geochemistry group that uses laboratory experiments and work in natural systems to interrogate how reactions between Fe- and S-bearing rocks and anoxic waters drive electron flow and the formation of labile energy carriers that can be harnessed for microbial metabolism and/or protometabolic networks as fluids circulate beneath the surface of the Earth.