In Investigation 2, we focus on simulating the geological disequilibrium in hydrothermal systems, and determining the role of minerals in harnessing these gradients toward the emergence of metabolism. Biological enzymes utilize catalytic metal sulfide active sites as well as “engines” (such as electron bifurcators, to couple endergonic and exergonic reactions); these components strongly resemble minerals found in hydrothermal environments and suggest that perhaps similar processes could have been driven geologically at the origin of life. We conduct laboratory experiments to simulate these primordial geological components, and the feedbacks that might have occurred to drive the emergence of metabolism in a seafloor system on the early Earth or any wet rocky planet.
Our lab work focuses on two main themes: first, we grow simulated hydrothermal chimneys to simulate the far-from-equilibrium conditions of alkaline vents and the electrical energy they produce that can drive carbon fixation; second, we investigate the ability of “green rust” – a catalytic iron oxyhydroxide mineral found in hydrothermal environments - to drive organic synthesis and proto-metabolic networks. Our simulated hydrothermal chimneys are small ‘chemical garden batteries’ which generate electrical potential and current (the magnitude of which depends on the specific reactants present) and we have also developed methods to vary the geochemical gradients by ‘switching’ hydrothermal fluid compositions during chimney growth, as may happen in a natural setting as the geochemistry evolves. Some reactions of interest on these electrochemically active chimneys include reduction/oxidation of geological carbon dioxide and methane with catalytic iron-nickel sulfides, and nitrogen chemistry and amino acid synthesis driven by green rust. From simulating the generation of electrical energy in hydrothermal chimneys, to exploring the prebiotic chemistry driven by the catalytic minerals within, this work is revealing the complex network of reactions that might have occurred in a hydrothermal mound on the seafloor of the early Earth – and perhaps also on icy worlds such as Europa or Enceladus that might also host a water-rock interface.
Barge, L. M., Abedian, Y., Doloboff, I. J., Nunez, J. E., Russell, M. J., Kidd, R. D., et al. Chemical Gardens as Flow-through Reactors Simulating Natural Hydrothermal Systems. J. Vis. Exp. (105), e53015, doi:10.3791/53015 (2015).
Here we report experimental simulations of hydrothermal chimney growth using injection chemical garden methods. The versatility of this type of experiment allows for testing of various proposed ocean / hydrothermal fluid chemistries that could have driven reactions toward the origin of life in environments on the early Earth, early Mars, or even other worlds such as the icy moons of the outer planets.
From Chemical Gardens to Chemobrionics
Laura M. Barge, Silvana S. S. Cardoso, Julyan H. E. Cartwright, Geoffrey J. T. Cooper, Leroy Cronin, Anne De Wit, Ivria J. Doloboff, Bruno Escribano, Raymond E. Goldstein, Florence Haudin, David E. H. Jones, Alan L. Mackay, Jerzy Maselko, Jason J. Pagano, J. Pantaleone, Michael J. Russell, C. Ignacio Sainz-Diaz, Oliver Steinbock, David A. Stone, Yoshifumi Tanimoto, and Noreen L. Thomas
Chemical Reviews 2015 115 (16), 8652-8703
In this review we recount the history of chemical-garden
studies, we survey the state of knowledge in this
field, and we give
overviews of the new fundamental understanding and of the
technological applications that these self-assembling precipita-
tion-membrane systems are providing.