"If sugar's in space, it's an important thing," Ziurys said in a telephone interview. "You add a few more carbons, and you end up with a sugar called ribose, and ribose is an essential component" of DNA and RNA.
What that means, however, is anybody's guess: "So suppose we have these interstellar clouds that are producing sugar molecules, and they're found throughout the galaxy," Ziurys said. "The big question is: Did the basic ingredients of life begin out in these clouds or on a planet?"
The simple sugar molecule glycolaldehyde was found in this dust and gas cloud, Sagittarius B2. The colors indicate radio emissions of different strengths.
(R. Gaume, M. Claussen, C. De Pree -- National Science Foundation)
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"We don't have a clue," Sandford said. "This seems to raise the odds that life could get started out there, but we don't know. That's why most of these arguments tend to be of a general nature."
In our solar system, and presumably elsewhere, the colder reaches of space are areas where particles of dust, ice and other debris bond in ever-larger clumps that eventually become comets.
Most comets in the solar system were formed about 4.5 billion years ago near the planets Uranus and Neptune and were subsequently cast into deep space well beyond Pluto. They reenter the solar system when nearby stars or large planets perturb their orbits.
Scientists long ago raised the possibility that early impacts from comets -- or asteroids from the belt between Mars and Jupiter -- may have brought Earth most of its water supply as well as the sugars and other compounds that served as the building blocks of life. The Green Bank research provides further evidence that this may have occurred.
Once liberated from their icy embrace and allowed to steep in warm water on the Earth's surface, the sugars could have combined with other carbon compounds to form ribose and, eventually, DNA and RNA.
But while this view appears to clash with more traditional thinking -- that the early Earth mixed its own soup without any help from space -- there is no reason why both phenomena could not have occurred.
"Current thinking is that sugars formed on the planet, but they could have been deposited on the planet by a comet or by interstellar dust," Ziurys said. "The important thing is that one method does not exclude the other."
And "nothing says that the stuff that fell out of the sky was the key thing, or the stuff that came from hydrothermal vents was the key thing, or the stuff that was struck by lightning was the key thing," Sandford said. "In the end, the chemical system that made life on Earth wasn't worried about 'Made in' labels. It just grabbed what it needed."
