New Origin of Life Proposed: Zinc & Zap

The Miller-Urey experiment, conducted by chemists Stanley Miller and Harold Urey in 1953, is the classic experiment on the origin of life. It established that the early Earth atmosphere, as they pictured it, was capable of producing amino acids, the building blocks of life, from inorganic substances.

Now, more than 55 years later, two scientists are proposing a hypothesis that could add a new dimension to the debate on how life on Earth developed.

Armen Mulkidjanian of the University of Osnabrueck, Germany and Michael Galperin of the U.S. National Institutes of Health present their hypothesis and evidence in two papers published and open for review in the web site Biology Direct.

The scientists suggest that life on Earth originated at photosynthetically active porous structures, similar to deep-sea hydrothermal vents, made of zinc sulfide (more commonly known as phosphor). They argue that under the high pressure of a carbon-dioxide-dominated atmosphere, zinc sulfide structures could form on the surface of the first continents, where they had access to sunlight. Unlike many existing theories that suggest UV radiation was a hindrance to the development of life, Mulkidjanian and Galperin think it actually helped.

"The problem of the origin of life is such that you have to answer a set of different questions to explain how life has originated," says lead author Mulkidjanian. "We just provide answers to the problem of energetics of the origin of life."

Altering the Early Atmosphere

According to Mulkidjanian, the debate about whether life could arise from chemical reactions began to change when scientists started to question the atmospheric conditions used by Miller and Urey. In their famous experiment, Miller and Urey replicated the early Earth atmosphere with a mixture of methane, hydrogen, ammonia and water vapor. This mixture, along with some "sparks" which simulated lightning, led to the formation of amino acids. With this setup, Miller and Urey assumed that the early Earth had a reducing atmosphere, which meant it had large amounts of hydrogen and almost no oxygen. link...