A research team has identified erythrulose, a four-carbon sugar, in a molecular cloud near the Galactic Centre - marking the first sugar confirmed in the interstellar medium and tracing a chemical path toward the building blocks of life.
Astronomers have detected erythrulose - a four-carbon sugar and the most complex non-cyclic molecule yet identified in interstellar space - in a dense molecular cloud near the Galactic Centre. According to a preprint submitted to Nature Astronomy on 2 June 2026, the discovery extends the known inventory of prebiotic molecules in the cosmos and traces a direct chemical path to threose, a key structural component of Threose Nucleic Acid (TNA), one of the leading candidate precursors to modern DNA and RNA.
The detection was made toward G+0.693-0.027, a molecular cloud embedded near the Galactic Centre that has become one of the most productive natural laboratories for interstellar organic chemistry. The research team, led by Izaskun Jimenez-Serra of the Centro de Astrobiologia (CAB, CSIC-INTA) in Spain, includes more than 54 co-authors from institutions across Spain, the Netherlands, Germany, Japan, Chile and the United States.
According to the preprint, the team used broadband spectral surveys from the Yebes 40-metre and IRAM 30-metre radiotelescopes, covering more than 91 gigahertz across multiple atmospheric windows - a broad and sensitive approach designed to pick up weak molecular emission lines that might otherwise be missed by narrower surveys.
Erythrulose is a chiral four-carbon ketose sugar with 14 atoms in its structure. The paper’s authors report that it is the largest non-cyclic molecule identified in the interstellar medium to date, and the first confirmed sugar of any kind found in space.
One result stood out as chemically unexpected. According to the preprint, erythrulose is at least eight times more abundant than analogous three-carbon sugars such as glyceraldehyde, which remain undetected despite years of sensitive searching. The team attributes this to erythrulose forming via a different route: rather than growing one carbon at a time, it assembles from two-carbon building blocks - glycolaldehyde and ethylene glycol - on the surfaces of interstellar dust grains, driven by cosmic ray bombardment and atomic hydrogen reactions. As reported by Universe Today, the confidence level for the detection sits at 99.8 percent.
The astrobiological significance centres on a well-established reaction pathway. In the presence of liquid water, ketose sugars like erythrulose readily isomerise into aldose sugars. Erythrulose would convert to threose, the four-carbon backbone of TNA. According to Universe Today’s coverage of the paper, TNA is widely regarded as a potential pre-RNA polymer - a structurally simpler, chemically stable forerunner to the nucleic acids that carry genetic information in all known life.
The paper’s authors note that large quantities of complex organic molecules were delivered to early Earth during the Late Heavy Bombardment, around 4 billion years ago. The detection of a sugar this structurally sophisticated in a galactic molecular cloud reinforces the hypothesis that the raw materials for prebiotic chemistry are not confined to Earth or even to our solar system.
The preprint has not yet completed peer review at Nature Astronomy. The G+0.693-0.027 cloud sits in the turbulent, radiation-rich environment of the Galactic Centre - conditions that differ substantially from the quieter star-forming regions where planetary systems like our own take shape. Whether comparable sugar concentrations exist in regions directly connected to planet formation is not yet established.
The pathway from interstellar erythrulose to functional TNA-like polymers also spans multiple unsolved steps: delivery to a planetary surface, concentration in liquid water, and the formation of nucleotide-like structures. Researchers note that confirming the broader significance of the discovery will require additional detections of sugar derivatives and, ideally, independent observations with facilities such as ALMA.
What the detection does establish, according to Jimenez-Serra and co-authors, is that the interstellar medium can serve as a viable sugar feedstock for prebiotic chemistry - not only in the early history of Earth, but potentially wherever molecular clouds and forming planetary systems interact across the galaxy.
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