How did Earth’s primitive chemistry get kick-started?

At alkaline hydrothermal vents at the bottom of oceans, says NASA JPL scientist
August 2, 2013
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A team of scientists at NASA’s Jet Propulsion Laboratory is testing whether organic molecules can be brewed in a simulated ocean vent. Pictured here is Lauren White, a member of the NASA Astrobiology Icy Worlds team. (Credit: NASA/JPL-Caltech)

Three new papers co-authored by Mike Russell, a research scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., strengthen the case that Earth’s first life began at alkaline hydrothermal vents at the bottom of oceans.

Scientists are interested in understanding early life on Earth because if we ever hope to find life on other worlds — especially icy worlds with subsurface oceans such as Jupiter’s moon Europa and Saturn’s Enceladus — we need to know what chemical signatures to look for.

Two papers published recently in the journal Philosophical Transactions of the Royal Society B provide more detail on the chemical and precursor metabolic reactions that have to take place to pave the pathway for life. Russell and his co-authors describe how the interactions between the earliest oceans and alkaline hydrothermal fluids likely produced acetate (comparable to vinegar).

The final cascade of engines leading to the emergence of life. The mantle convection engine delivers heat to the near surface and stresses the crust to effectively feed the serpentinization engine (a processes whereby rock is changed, with the addition of water into the crystal structure of the minerals found within the rock.engine). The photographic montage of a typical, scale invariant example of serpentinite, offers us a gallery view of the composite engine responsible for driving life into being. (Credit: Russell MJ, et al./Philosophical Transactions of the Royal Society B: Biological Sciences)

The acetate is a product of methane and hydrogen from the alkaline hydrothermal vents and carbon dioxide dissolved in the surrounding ocean. Once this early chemical pathway was forged, acetate could become the basis of other biological molecules. They also describe how two kinds of “nano-engines” that create organic carbon and polymers — energy currency of the first cells — could have been assembled from inorganic minerals.

A paper published in the journal Biochimica et Biophysica Acta analyzes the structural similarity between the most ancient enzymes of life and minerals precipitated at these alkaline vents, an indication that the first life didn’t have to invent its first catalysts and engines.

“Our work on alkaline hot springs on the ocean floor makes what we believe is the most plausible case for the origin of the life’s building blocks and its energy supply,” Russell said. “Our hypothesis is testable, has the right assortment of ingredients and obeys the laws of thermodynamics.”

Russell’s work was funded by the NASA Astrobiology Institute through the Icy Worlds team based at JPL, a division of the California Institute of Technology, Pasadena. The NASA Astrobiology Institute, based at NASA’s Ames Research Center, Moffett Field, Calif., is a partnership among NASA, 15 U.S. teams and 13 international consortia. The Institute is part of NASA’s astrobiology program, which supports research into the origin, evolution, distribution and future of life on Earth and the potential for life elsewhere.