Today’s Top Science Headline: Clue to the Mystery of Carbon’s Cosmic Origin Uncovered –“The Backbone of Life”




A chemical found in a distant gas cloud could help explain where planets like Earth get the seeds of life. Some 18 percent of the human body’s weight is carbon. The simple element is considered the backbone of life, and is also abundant in Earth’s rocks, atmosphere and oceans. Scientists don’t know how carbon first appeared on our planet, but now astronomers have discovered a special molecule in space that could help trace this essential element back to its source.

Researchers using the Green Bank Telescope, writes Clara Moskowitz in today's Scientific American, identified signatures of the molecule benzonitrile (C6H5CN) in a mass of gas and dust called the Taurus Molecular Cloud 1, which lies 430 light-years from Earth. The heart of benzonitrile is a six-carbon hexagon called benzene—a structure that puts the compound in the “aromatic” class of molecules and makes benzonitrile a building block for a group called polycyclic aromatic hydrocarbons (PAHs), which contain lots of carbon hexagons. Scientists think PAHs are incredibly common in the universe, yet astronomers have not identified a single such molecule in space. This new observation is the closest they have come.

“This study shows you have the first steps of PAHs, these first rings of benzene,” says Xander Tielens, an astrochemist at Leiden University in the Netherlands who was not involved in the research. “Then you can grow to bigger and bigger species. Understanding where these molecules come from and understanding what role they play in the inventory of space is a key goal of astronomy.” The findings were published today in Science and presented at a meeting of the American Astronomical Society in Washington, D.C.

The study may be a step toward explaining where planets like Earth got their carbon. The element starts out in the cores of stars, where it is a product of nuclear fusion. But when stars die and eject their materials into space, what happens to it? Scientists think the largest fraction—between 10 to 20 percent—becomes PAHs, which can form whenever a warm carbon-containing gas cools down. Eventually, do those PAHs find their way into the protoplanetary disks around stars that form planets and asteroids?

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The image at the top of the page shows a giant carbon star that requires a new theory that could significantly alter our understanding of what materials exist in interstellar space, and where water and life could exist in the universe.



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