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Astronomers have detected a true sugar in interstellar space for the first time, floating in a chemically rich cloud near the center of the Milky Way.
The molecule is called erythrulose. It is a four-carbon monosaccharide, or simple sugar, also found in raspberries. By itself, its discovery doesn’t mean that there’s life in outer space, but it does show that surprisingly complex ingredients for prebiotic chemistry can form before planets exist.
The molecule, called erythrulose, belongs to the same chemical family as the sugars that help build RNA and DNA. Basically, the raw materials needed for early biology need not have originated on Earth. They could have formed in space, become incorporated into asteroids and comets, and eventually landed on young planets.
A Sweet Signal From the Galactic Center
An international team led by Izaskun Jiménez-Serra, an astronomer at Spain’s Center for Astrobiology, identified erythrulose in a molecular cloud called G+0.693−0.027. The cloud lies in the Galactic Center region, about 27,000 light-years from Earth. It’s one of the richest known reservoirs of complex molecules in the Milky Way and has already yielded several compounds relevant to prebiotic chemistry.
Molecular clouds are enormous concentrations gas and dust. They often become stellar nurseries, where stars and planets begin to take shape. Scientists have identified hundreds of molecules in interstellar space, including an increasingly impressive collection of complex organic compounds. But until now, they hadn’t directly detected a true sugar there.
That was puzzling because sugars such as ribose and glucose have been found in meteorites andasteroid samples, including material from Bennu. Those discoveries hinted that space rocks may have delivered sugars to the young Earth. But finding a sugar already floating between stars goes a step further in proving the ingredients for life could have emerged in deep space.
Sugars are central to life as we know it. They can provide and store energy, form structural materials and make up part of the backbone of nucleic acids. RNA contains ribose, while DNA contains the closely related sugar deoxyribose. Erythrulose is not itself part of RNA or DNA, but it belongs to the same broad chemical world and could provide starting material for reactions involved in early genetic chemistry.
This is why the new find is so important.
True Sugar
Astronomers can’t go there and collect erythrulose or photograph individual molecules. Instead, they identified it through its rotational spectrum—essentially a molecular radio fingerprint.
Molecules rotate in space, and those rotations produce specific patterns of radio waves. By comparing signals from space with measurements made in the laboratory, researchers can tell which molecules are present, even from thousands of light-years away.
The search gained traction in 2022, when Emilio Cocinero, a physical chemist at the University of the Basque Country, shared laboratory data showing what erythrulose should look like to a radio telescope.
Jiménez-Serra was doubtful at first. “I said, ‘OK, why don’t you send me the information, and then I’ll check whether we see it in our data’,” she told Nature.
The fingerprint was there. Follow-up observations with the Yebes 40-meter and IRAM 30-meter radio telescopes confirmed 12 spectral lines that matched erythrulose—enough for the team to make the case that the sugar was present in G+0.693.
“This is an incredibly exciting result,” Brett McGuire, an astrochemist at the Massachusetts Institute of Technology, told Nature. “Astronomers have, for a very long time, been pushing to detect sugars in space.”
Erythrulose carries four carbon atoms, which places it firmly in the sugar family. That sets it apart from glycolaldehyde, a two-carbon molecule reported in interstellar space in 2000. Glycolaldehyde can take part in sugar-like chemistry, but chemists draw the line for true sugars at molecules with at least three carbon atoms.
Precursor to RNA
The finding also gives researchers a possible route from interstellar chemistry to early Earth.
During the Late Heavy Bombardment—a period about 4.1 billion to 3.9 billion years ago when asteroids and comets are thought to have battered the young planet—the researchers estimate that between 0.5 million and 50 million metric tons of erythrulose could have reached Earth’s surface.
That suggests that young planets may not have had to make all of life’s raw materials from scratch. Some could have arrived already formed, carried in from the same clouds that built star systems.
Erythrulose is especially interesting because, in water, it can change into threose, a sugar tied to early genetic chemistry, considered a possible precursor to RNA-like molecules.
The next test is whether space can make even larger sugars. Ribose, the five-carbon sugar in RNA, remains the grail. Finding it in interstellar space would bring astronomers much closer to a molecule at the heart of biology.
For now, erythrulose expands the search. A sugar once known mostly from raspberries and self-tanners has become evidence that the chemistry behind life may begin far earlier, in the dark clouds where stars are born.
The study was published in the journal Nature Astronomy.
This story originally appeared on ZME Science. Want to get smarter every day? Subscribe to our newsletter and stay ahead with the latest science news.
