July 31, 2013
Origins Of Life On Earth May Help Hunt For Life On Other Planets
Brett Smith for redOrbit.com - Your Universe Online
Tracing the origins of life isn't only central to understanding our own history, it can also be important for discovering life on other planets.
Two recently published papers -- 'Beating the acetyl coenzyme A-pathway to the origin of life' and 'The inevitable journey to being' -- in the Philosophical Transactions of the Royal Society B add supporting details to the theory life on Earth began near hydrothermal vents in the ocean floor. For life to have originated there, several metabolic and chemical reactions must have taken place and the new research describes how the interactions between hydrothermal fluids and the surrounding ocean facilitated these life-giving reactions.
"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," said Michael Russell, a NASA geochemist and co-author of both papers. "Our hypothesis is testable, has the right assortment of ingredients and obeys the laws of thermodynamics."
The work done by Russell and his colleagues focuses specifically on how early, simple forms of life accessed and exploited an energy source. This process used external energy to constantly pump protons into biological membrane. As these protons attempt to flow back across that membrane, they passed through a turbine-like molecular engine that generated a chemical fuel called ATP instead of electricity.
The odd and inefficient process would be akin to pumping water behind a dam and then letting it flow down through a turbine and out the dam to generate power. However, the new study suggests active "pumping" wasn't necessary as the proton gradient was already there to be exploited.
According to Russell's theory, which he first postulated 25 years ago, life arose out of a natural consequence of a geochemical process called serpentinization.
Serpentinization occurs when water enters hot, newly formed ocean crust. There it chemically reacts with the minerals in the rocks to create extremely alkaline liquid. This high-pH fluid is sent up to the ocean's surface where, particularly in the case of the primordial ocean, it interacts with cooler, low-pH water to generate precipitates that fall back down and create chimney-like towers on the ocean floor. These towers contain countless cell-like compartments, each encased in mineral membranes -- analogous to our own cells.
The membranes establish a proton gradient that strikingly resembles the cell membranes of all living things on earth, complete with simple, "mineral-based" forms of energy production that allow protons to exit the membrane.
"So, if the Russell theory is correct, it is suddenly obvious why we pump protons and use this silly method," said co-author Elbert Branscomb, from the Institute for Genomic Biology at the University of Illinois at Urbana-Champaign. "We got stuck on this 'free lunch' energy system when life was born, developed a lot of fancy machinery to use it, and have never severed that umbilicus since."
The study authors suggested if this primitive system did lead to life on Earth, then it could be replicated on other planets. They are currently working up experimental models to replicate and test the crucial principals of Russell's theory.