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KNOXVILLE, Tenn.– The recipe for life on Earth may include ingredients from outer space, a University of Tennessee-Knoxville geologist said Wednesday.

 Dr. Hap McSween said elements such as carbon, nitrogen and oxygen are created inside of stars and spewed across the cosmos when the stars explode. Extreme conditions in space turn these elements into organic molecules such as amino acids, which are chief components of proteins necessary for life, he said.

“These molecules are not complex by the biochemical standards of living systems but they represent a major step in organic evolution,” McSween said.

 McSween said the organic molecules are trapped in ice and rocks in space. For example, Comet Halley is believed to be 25 percent organic matter. Some meteorites contain amino acids enriched with deuterium, a hydrogen isotope that shows the molecules were born in outer space.

 Comets and other bodies carrying these organic molecules could have crashed to Earth’s primordial surface billions of years ago, introducing a key ingredient in the formula for life, McSween said.

 Other theories suggest biological compounds formed on Earth. In 1953, experiments by Harold C. Urey and Stanley Miller of the University of Chicago combined methane, ammonia, water, hydrogen and electricity to recreate early Earth conditions. The system created organic compounds and amino acids, suggesting that the ingredients necessary for life would have been abundant on the primitive planet.

 However, McSween said organic compounds found in meteorites and proof that rocks can be blasted from one planet to another during large impacts shows that organic matter or even primitive life forms such as bacterial spores could be exchanged between worlds.

 “It is plausible that life did not require Miller-Urey type synthesis of biogenic compounds,” McSween said. “The history of the Earth’s biogenic elements reveals that life may not have had to start from scratch.”

 McSween is scheduled to give a presentation Oct. 20 titled “Life’s Recipe: Extraterrestrial Sources of Biogenic Elements and Compounds” at the Geological Society of America annual meeting in Salt Lake City.

 McSween was a member of NASA’s Mars Pathfinder team which landed a probe on Mars in July. He also examined a Martian meteorite which NASA scientists said contains proof of past life of Mars.


 Contact: Dr. Hap McSween (423-974-9805)