Partial Ingredients for DNA and Protein Found Around Star
NASA's Spitzer Space Telescope has discovered some of life's most basic ingredients
in the dust swirling around a young star. The ingredients - gaseous precursors to DNA
and protein - were detected in the star's terrestrial planet zone, a region where rocky
planets such as Earth are thought to be born.
Image right: This artist's concept illustrates a solar system that is a much younger version of our own. Dusty disks, like the one shown here circling the star, are thought to be the breeding grounds of planets, including rocky ones like Earth. Image credit: NASA/JPL-Caltech
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The findings represent the first time that these gases, called acetylene and hydrogen
cyanide, have been found in a terrestrial planet zone outside of our own.
"This infant system might look a lot like ours did billions of years ago, before life
arose on Earth," said Fred Lahuis of Leiden Observatory in the Netherlands and the
Dutch space research institute called SRON. Lahuis is lead author of a paper to be
published in the Jan. 10 issue of the Astrophysical Journal Letters.
Lahuis and his colleagues spotted the organic, or carbon-containing, gases around a
star called IRS 46. The star is in the Ophiuchus (pronounced OFF-ee-YOO-kuss), or
"snake carrier," constellation about 375 light-years from Earth. This constellation
harbors a huge cloud of gas and dust in the process of a major stellar baby boom.
Like most of the young stars here and elsewhere, IRS 46 is circled by a flat disk
of spinning gas and dust that might ultimately clump together to form planets.
When the astronomers probed this star's disk with Spitzer's powerful infrared
spectrometer instrument, they were surprised to find the molecular "barcodes" of
large amounts of acetylene and hydrogen cyanide gases, as well as carbon dioxide gas.
The team observed 100 similar young stars, but only one, IRS 46, showed unambiguous
signs of the organic mix.
"The star's disk was oriented in just the right way to allow us to peer into it,"
The Spitzer data also revealed that the organic gases are hot. So hot, in fact,
that they are most likely located near the star, about the same distance away
as Earth is from our sun.
"The gases are very warm, close to or somewhat above the boiling point of water
on Earth," said Dr. Adwin Boogert of the California Institute of Technology, Pasadena.
"These high temperatures helped to pinpoint the location of the gases in the disk."
Organic gases such as those found around IRS 46 are found in our own solar system,
in the atmospheres of the giant planets and Saturn's moon Titan, and on the icy
surfaces of comets. They have also been seen around massive stars by the European
Space Agency's Infrared Space Observatory, though these stars are thought to be
less likely than sun-like stars to form life-bearing planets.
Here on Earth, the molecules are believed to have arrived billions of years ago,
possibly via comets or comet dust that rained down from the sky. Acetylene and
hydrogen cyanide link up together in the presence of water to form some of the
chemical units of life's most essential compounds, DNA and protein. These chemical
units are several of the 20 amino acids that make up protein and one of the four
chemical bases that make up DNA.
"If you add hydrogen cyanide, acetylene and water together in a test tube and
give them an appropriate surface on which to be concentrated and react, you'll get a
slew of organic compounds including amino acids and a DNA purine base called adenine,"
said Dr. Geoffrey Blake of Caltech, a co-author of the paper. "And now, we can detect
these same molecules in the planet zone of a star hundreds of light-years away."
Follow-up observations with the W.M. Keck Telescope atop Mauna Kea in Hawaii confirmed
the Spitzer findings and suggested the presence of a wind emerging from the inner region
of IRS 46's disk. This wind will blow away debris in the disk, clearing the way for
the possible formation of Earth-like planets.
The Jet Propulsion Laboratory manages the Spitzer Space Telescope mission for NASA's
Science Mission Directorate, Washington. Science operations are conducted at the Spitzer
Science Center at Caltech. JPL is a division of Caltech. Spitzer's infrared spectrograph
was built by Cornell University, Ithaca, N.Y. Its development was led by Dr. Jim
Houck of Cornell.
For graphics and more information about Spitzer, visit http://www.spitzer.caltech.edu/spitzer
For more information about NASA and agency programs on the Web, visit http://www.nasa.gov/home/
Whitney Clavin (818) 354-4673