Monday, November 1, 2010

Tracing our origins to the stars

The color mosaic of the Orion Nebula and nearby star-forming region. Credit: NASA, ESA, M. Robberto (Space telescope Science Institute) and the Hubble Space Telescope Orion Treasury Project Team.

Discover Magazine writes about how scientists are searching for the origins of life in deep space by teasing out different strands of the story of prebiotic chemistry:

Carbon, hydrogen, oxygen and other atoms knock about in nebulas, sometimes freely and sometimes bound up with ice and dust. They arrange themselves into elaborate molecular structures. Meteorites abound with organic compounds, which rain down on any nearby planets.

Helping to weave all those strands into a single, elegant narrative is an Emory University astrochemist with a providential name: Susanna Widicus Weaver. Through a series of models and experiments, she has demonstrated that ultraviolet radiation can break chemical bonds and split molecules into highly reactive fragments called radicals. It is difficult for radicals to do much at -440 degrees F, but when the temperature warms even slightly (as when a star begins to form), the radicals merge to form larger molecules …. In a major 2008 paper, Weaver predicted an abundance of such radicals in dust clouds. A thorough search of interstellar ice grains by infrared astronomers should determine whether radicals indeed play a primary role in constructing prebiotic molecules. …

We know that meteorites contain amino acids and even nucleobases, but not whether they scooped up those molecules from dust clouds or created them later, on their interplanetary course. “We really don’t know where the chemistry in the dust cloud stops and where the chemistry in meteorites starts up,” Weaver says. She notes that the answer has tremendous implications for one of science’s most fundamental questions: How common is life throughout the universe?

Read the full article in Discover.

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