Astronomers have detected erythrulose, a four-carbon sugar, in a molecular cloud near the center of the Milky Way, marking the first reported discovery of a true sugar in the interstellar medium, the gas and dust between stars.
The finding could help scientists explain how some prebiotic sugars may have formed before the solar system took shape and how minor bodies may later have carried them to the young Earth, according to a study published Monday in Nature Astronomy.
Erythrulose’s significance in space comes from its chemistry. Unlike glycolaldehyde, a two-carbon compound previously described as sugar-like, erythrulose has the carbon framework needed to qualify as a true sugar.
How scientists detected the sugar
Researchers identified erythrulose in G+0.693-0.027, a chemically rich cloud roughly 27,000 light-years from Earth near the Milky Way’s center.
The team used the Yebes 40-meter telescope in Guadalajara, Spain, and the IRAM 30-meter telescope in Granada, Spain. Astronomers compared the cloud’s radio-frequency patterns with laboratory measurements of gaseous erythrulose and found 12 matching sets of spectral lines representing 17 individual transitions.
Six of the line sets were predominantly unblended. The researchers calculated a 0.2% probability that those six alignments occurred by chance, providing strong statistical support for the identification.
The result also surprised the team. Erythrulose appeared at least eight times more abundant than the three-carbon sugars glyceraldehyde and dihydroxyacetone, which the survey did not detect. In many molecular families, abundance usually falls as molecules gain carbon atoms.
Models point to formation on icy dust grains
Quantum-chemical calculations and astrochemical models indicate that erythrulose can form on icy interstellar dust grains from two simpler two-carbon molecules, glycolaldehyde and ethylene glycol. Radiation can activate the smaller compounds, while shocks inside the cloud can release newly formed molecules from the ice into gas, where radio telescopes can detect them.
The researchers described erythrulose as the largest non-cyclic molecular species identified in the interstellar medium. Its 14-atom structure also makes it the first detected interstellar molecule containing four oxygen atoms and only the second chiral molecule found there. Chiral molecules can exist in two mirror-image forms.
What the finding means for life’s origins
The discovery does not show that life began in space. It does show that a chemically relevant sugar can form under interstellar conditions.
Erythrulose is not itself a component of DNA or RNA. In water, however, it can rearrange into related sugars, including threose and erythrose, that researchers connect to pathways for making ribose and early nucleic acid components.
Under conservative assumptions, the study estimated that 0.5 billion to 50 billion kilograms of erythrulose could have reached Earth during the Late Heavy Bombardment between 4.1 billion and 3.9 billion years ago. The authors also noted that scientists continue to debate the extent and intensity of that bombardment.
“The key ingredients for the origin of life could be present in other regions across the galaxy, opening the possibility for life to develop elsewhere in the universe,” study author Izaskun Jiménez-Serra said, The Associated Press reported.
University of Arizona astrophysicist Erika Hamden, who was not involved in the study, called erythrulose “a pristine example of the stuff that’s just floating out in the galaxy,” according to the AP.
The finding adds to evidence that prebiotic compounds can form beyond Earth. NASA reported on December 2, 2025, that samples collected from asteroid Bennu contained ribose and glucose. As previously reported by The Dallas Express, scientists have also identified phosphorus and organic compounds connected to habitability in material erupting from Saturn’s moon Enceladus.
Provided by Dallas Express
