Life on the Rocks: Microbes, Mines, and Martians

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Picture a world before the dinosaurs when plants and animals hadn't evolved yet. Where volcanoes gave birth to new land and spewed toxic gases into an oxygen-free atmosphere. Where the continents were just being born and where the oceans were almost free of life except for tiny single-celled organisms. But what was there to eat? Look a little deeper. In the cracks and crevices deep beneath the seafloor, seawater seeps down into the rocks, gets heated, and strips metals that are later concentrated in jets of dense black "smoke" that exit through mineralized chimneys rising like misshapen spires into the darkness. As these chimneys grow they sometimes crumble under their own weight, forming mounds that briefly expose their glistening riches of metal sulphides before they quickly rust in the cold, oxidized, salty seawater. In these deep, dark, watery places microbes have been found that colonize the sulphide mounds and glassy lavas beneath, extracting nutrients from this unlikely food source. Lavas continuously erupt at undersea volcanoes that form mountain chains beneath the sea like seams on a baseball. These are dynamic environments where globally significant chemical, biological, and heat fluxes occur between the geo-, hydro-, and atmosphere. The formation of new crust and the reincorporation of aged crust into the mantle at subduction zones are perhaps the most fundamental components of the plate tectonic cycle. These processes control the physiography of the Earth and the chemical and thermal evolution of the crust and mantle. The guiding principle of the proposed research is the investigation of water-rock-microbial processes in Earth and planetary materials over timescales of billions of years. This field is at the forefront of interdisciplinary study. My group uses a multidisciplinary approach combining geochemical, mineralogical, petrological, and imaging techniques to study modern and ancient hydrothermal systems. Our work focuses on both Earth and planetary materials. We have pioneered research on the biogeochemical effects of water- rock-microbial interactions using novel geochemical techniques to detect microbial biosignatures and constrain environmental conditions in rocks that have undergone deformation and metamorphism. This has been further applied to geochemical processes that lead to metal accumulations in the crust and create economic ore deposits. More recently, we have applied our cutting-edge techniques to quantify and constrain the creation and alteration of meteorites. Although these topics may at first glance seem to be somewhat disparate they are inextricably intertwined. The theme that runs through all these processes and ties them together is that of water- rock-microbial interactions through geological time. Outcomes of this research will be of interest and importance to both academic and applied researchers and practitioners with impacts that will benefit society from both an economic as well as basic understanding.