June 1, 2007

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Gary Campbell, garycamp@asu.edu
(480) 965-7209
February 14, 2003
Sources: Sandra Pizzarello, (480) 965-3370

Researchers find space, earth may have had complimentary roles in origins of life

Scientists have debated whether the origins of life come from outer space or from Earth for years. Now a new study shows the two forces may have had a dual, complimentary role.

The findings by Sandra Pizzarello of the ASU chemistry & biochemistry department, and Arthur Weber, from the SETI Institute of the NASA Ames Research Center, will be presented at the NASA Astrobiology Institute General Meeting Feb. 10 - 13 at ASU. The preliminary findings show organic compounds from endogenous formation (from Earth) and exogenous delivery (from meteorites) could have reacted together under early Earth conditions to create some of the early building blocks of life.

In the debate over the origins of life, one major hypothesis holds that the first building blocks of life came from carbonaceous chondrites (meteorites). These meteorites contain a complex grouping of organic compounds (particularly amino acids and sugar alcohols) that are similar and in many cases identical to those found on Earth. The theory holds that the meteorites that frequently shower the Earth, first delivered these building blocks to the planet.

Another theory is that organics needed for life were synthesized "de novo" on the planet from simple compounds and then evolved into more complex and polymeric material.

Both of the theories take an either/or approach, excluding any possible assistance from the other theory. Pizzarello and Weber took a third approach, that of a combination of both methods.

"We wanted to see if something we know was part of an exogenous delivery could interact with some of the proposed endogenous syntheses of early Earth," says Pizzarello.

The key to the study was to consider homochirality, i.e., the one-handedness of amino acids and sugars that are important to the organization and function of biopolymers. Pizzarello and Weber showed that in a reaction in an environment similar to that of early Earth, the amino acids can catalyze non-racemic sugar formations. The sugars would then go on to further react and produce other and more complex compounds.

"We found that the catalytic effect of amino acids, including that of one abundant in meteorites, includes the transfer of asymmetry," she says.

The finding, while still preliminary, will lead to greater exploration of the concept that life began as more of a collaborative effort than a simple either/or proposition.

"It's something no one has really ever looked at," she says.