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Sugar in Space

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see captionJune 20, 2000 -- The prospects for life in the Universe just got sweeter, with the first discovery of a simple sugar molecule in space. The discovery of glycolaldehyde in a giant cloud of gas and dust near the center of our own Milky Way Galaxy was made by scientists using the National Science Foundation's 12 Meter Telescope, a radio telescope on Kitt Peak, Arizona.

"The discovery of this sugar molecule in a cloud from which new stars are forming means it is increasingly likely that the chemical precursors to life are formed in such clouds long before planets develop around the stars," said Jan M. Hollis of the NASA Goddard Space Flight Center in Greenbelt, MD.

Above: The National Radio Astronomy Observatory's 12 Meter Telescope was used by Jan Hollis (NASA/Goddard), Frank J. Lovas (University of Illinois) and Philip R. Jewell (NRAO/Green Bank) to detect the sugar molecule glycolaldehyde in an interstellar molecular cloud. Credit: NRAO.

"This discovery may be an important key to understanding the formation of life on the early Earth," agreed Philip Jewell of the National Radio Astronomy Observatory (NRAO). Conditions in interstellar clouds may, in some cases, mimic the conditions on the early Earth, so studying the chemistry of interstellar clouds may help scientists understand how bio-molecules formed early in our planet's history. In addition, some scientists have suggested that Earth could have been "seeded" with complex molecules by passing comets, made of material from the interstellar cloud that condensed to form the Solar System.

see captionGlycolaldehyde, an 8-atom molecule composed of carbon, oxygen and hydrogen, can combine with other molecules to form the more-complex sugars Ribose and Glucose. Ribose is a building block of nucleic acids such as RNA and DNA, which carry the genetic code of living organisms. Glucose is the sugar found in fruits. Glycolaldehyde contains exactly the same atoms, though in a different molecular structure, as methyl formate and acetic acid, both of which were detected previously in interstellar clouds. Glycolaldehyde is a simpler molecular cousin to table sugar, the scientists say.

Left: Glycolaldehyde, the simplest sugar, compared to more complex sugar forms that occur naturally (i.e., the D-sugars). Glycolaldehyde is the only member of the sugar family yet detected in interstellar clouds. Note that the structure of glycolaldehyde is contained in both Ribose and Glucose. Ribose sugars make up the backbone of the ribonucleic acid (RNA) molecule which is involved in protein synthesis in living cells. Glucose, the most common sugar, occurs in plant saps and fruits. Credit: NRAO.

The sugar molecule was detected in a large cloud of gas and dust some 26,000 light-years away, near the center of our Galaxy. Such clouds, often many light-years across, are the material from which new stars are formed. Though very rarefied by Earth standards, these interstellar clouds are the sites of complex chemical reactions that occur over hundreds of thousands or millions of years. So far, about 120 different molecules have been discovered in these clouds. Most of these molecules contain a small number of atoms, and only a few molecules with eight or more atoms have been found in interstellar clouds.

see captionRight: Jan M. Hollis of the NASA Goddard Space Flight Center in Greenbelt, MD. Credit: NASA/GSFC

"Finding glycolaldehyde in one of these interstellar clouds means that such molecules can be formed even in very rarefied conditions," added Hollis. "We don't yet understand how it could be formed there. A combination of more astronomical observations and theoretical chemistry work will be required to resolve the mystery of how this molecule is formed in space."

"We hope this discovery inspires renewed efforts to find even more kinds of molecules, so that, with a better idea of the total picture, we may be able to deduce the details of the prebiotic chemistry taking place in interstellar clouds," Hollis said.

see captionThe discovery was made by detecting faint radio emission from the sugar molecules in the interstellar cloud. Molecules rotate end-for-end, and as they change from one rotational energy state to another, they emit radio waves at precise frequencies. The "family" of radio frequencies emitted by a particular molecule forms a unique "fingerprint" that scientists can use to identify that molecule. The scientists identified glycolaldehyde by detecting six frequencies of radio emission in what is termed the millimeter-wavelength region of the electromagnetic spectrum -- a region between more-familiar microwaves and infrared radiation.

Above: The giant molecular cloud, known as Sagittarius B2 (North), as seen by the NSF's Very Large Array (VLA) radio telescope in New Mexico. This is the cloud in which scientists using the 12 Meter Telescope detected the simple sugar molecule glycolaldehyde. This VLA image shows hydrogen gas in a region nearly 3 light-years across. The 12 Meter Telescope studied this region at much shorter wavelengths, which revealed the evidence of sugar molecules. CREDIT: R. Gaume, M. Claussen, C. De Pree, W.M. Goss, D. Mehringer, NRAO/AUI/NSF.

The NRAO 12 Meter Telescope used to detect the sugar molecule has been a pioneer instrument in the detection of molecules in space. Built in 1967, it made the first detections of dozens of the molecules now known to exist in space, including the important first discovery of carbon monoxide, now widely used by astronomers as a signpost showing regions where stars are being formed. It is scheduled to be closed at the end of July, in preparation for the Atacama Large Millimeter Array, an advanced system of 64 radio-telescope antennas in northern Chile now being developed by an international partnership.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.Web Links

Scientists Discover Sugar in Space -- a Goddard Space Flight Center press release

Scientists Discover Sugar in Space -- NRAO press release, the same as the Goddard version but with more pictures.