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Creation of Life

April 23, 2014

An international team has reformulated the theory of the creation of life at hydrothermal vents in the Earth's primal oceans, proposing a membrane-driven process making use of two energy gradients. This location for the initial emergence of life on Earth would be significant because any particular vent may last no longer than 30,000 years. That is, the first living protocell would have to be created in this time span. In fact, the speed at which life has appeared is surprising. The Earth formed about 4.5 billion years ago and underwent a catastrophic collision 50 million years later that created the Moon. A heavy bombardment by asteroids followed 600 million years later, tailing off about 3.8 billion years ago. The oldest fossil evidence of life is about 3.8 billion years old.

The team, led by Michael J. Russell of NASA Jet Propulsion Laboratory, reason that early evolution did not primarily involved emergence of prebiotic chemistry from which ever more complex organic chemicals eventually come together to assemble a living cell. Rather they focus on the evolution of nanoengines, precursors of the molecular motors that move essential chemicals within and through the membranes that all cells possess. This focus stems from the viewpoint that membrane-spanning energy gradients rather than organic chemical reactions play a vital role in life's operations, and that complex inorganic membranes precipitated in thermal vents in the early ocean could play that role. If so, some evidence of membrane transfer should be found in contemporary vents. Alternatively, experiments with water and suitable minerals at high pressures should indicate the validity of the approach.

How life originated from non-living materials is important to us in understanding our own origins and evolution. The conditions under which such a process can occur is also important in gauging the likelihood that life has emerged elsewhere in the universe. We have speculated from ancient times whether we are alone or whether other civilizations have evolved around other stars. The realization that there are tens of billions of planets in our Galaxy have given increased emphasis to these speculations.

We search for life in the universe on the assumption that there are other planets that formed in the way that Earth formed. So, the emergence of life on Earth out of physical processes is likely to be mirrored on other planets. However, we do not know the process that produced life in Earth's early environment. So if we find evidence of the early stages of chemical and biological evolution elsewhere, we may learn more about out own evolution. For example, if evidence of living cells is found on Mars in the absence of hydrothermal vents, then Mars has seen an alternative path for the creation of life out of non-living matter. Therefore other sources of life may have existed on Earth, or hydrothermal vents did not produce living cells. (More)

Reference

The Drive to Life on Wet and Icy Worlds by Michael J. Russell, Laura M. Barge, Rohit Bhartia, Dylan Bocanegra, Paul J. Bracher, Elbert Branscomb, Richard Kidd, Shawn McGlynn, David H. Meier, Wolfgang Nitschke, Takazo Shibuya, Steve Vance, Lauren White, and Isik Kanik. Astrobiology, 14, 309, 2014.