A team of international astronomers has detected erythrulose — a four-carbon sugar molecule found naturally in raspberries and kiwis — drifting inside a massive cloud of gas and dust near the center of the Milky Way, roughly 26,745 light-years from Earth. The discovery, published on July 13, 2026, in the journal Nature Astronomy, marks the first time a sugar has been directly observed in interstellar space and provides new evidence that the molecular ingredients necessary for life can form naturally in the cosmos long before stars and planets take shape.
Key Takeaways
- Erythrulose, a four-carbon sugar molecule, has been detected for the first time in interstellar space within molecular cloud G+0.693−0.027, located near the Milky Way’s galactic center
- The detection was made using the Yebes 40-meter and IRAM 30-meter radio telescopes in Spain, with 12 independent spectral lines matching the laboratory signature of erythrulose
- Erythrulose was found to be at least eight times more abundant than comparable three-carbon sugars, which were not detected at all in the same region — a finding that challenges existing models of how complex molecules build up in space
- Sugars serve as the structural backbone of DNA and RNA and play a fundamental role in cellular energy, making their presence in interstellar space directly relevant to understanding how life’s chemical building blocks form
- The research was led by Izaskun Jiménez-Serra of the Spanish National Research Council and published in Nature Astronomy
Why Is Finding Sugar in Interstellar Space Significant?
Sugars are among the foundational molecules of biology. They form the structural backbone of DNA and RNA, serve as metabolic fuel for cells, and function as energy-storage polymers. A central question in origin-of-life research has been how these molecules first appeared on early Earth, given that laboratory experiments simulating prebiotic conditions have consistently struggled to produce sugars in sufficient quantities. Scientists had previously detected sugar compounds in asteroids and meteorites — NASA’s OSIRIS-REx mission found ribose and other sugars in samples from the asteroid Bennu — but those discoveries left open the question of whether sugars could form even earlier in the cosmic timeline, in the interstellar medium itself, before asteroids and planets had begun to coalesce.
The detection of erythrulose in a molecular cloud answers that question directly. Molecular clouds are vast, irregular concentrations of gas and dust that exist between stars. They are sometimes called “stellar nurseries” because stars eventually form within them, but at the stage where erythrulose was detected, no stars or planets are present. The sugar molecule is forming in a pre-stellar environment, which means the chemical raw material for life can assemble before planetary systems even exist.
How Was the Discovery Made?
The research team, led by Izaskun Jiménez-Serra of the Centro de Astrobiología at the Spanish National Research Council in Madrid, used two radio telescopes in Spain — the Yebes 40-meter telescope and the IRAM 30-meter telescope — to conduct ultrasensitive, broadband spectroscopic surveys of the molecular cloud G+0.693−0.027, a dense gas and dust formation located in the galactic center region.
Every molecule emits radiation at characteristic frequencies, producing a unique spectral fingerprint. The team identified 12 independent spectral lines in the cloud’s emissions that matched the laboratory spectrum of erythrulose. That laboratory reference data was provided by Emilio Cocinero, a physical chemist at the University of the Basque Country in Leioa, Spain, who had measured erythrulose’s spectroscopic signature in 2022 and shared the data with the astronomical team.
Erythrulose, with 14 atoms in its structure, is now the largest non-cyclic molecular species identified in the interstellar medium and the first detected molecule containing four oxygen atoms. It is also only the second chiral molecule — a molecule with a specific handedness, or mirror-image asymmetry — ever reported in interstellar space. Chirality matters because biological molecules on Earth overwhelmingly favor one handedness over the other, and understanding where that preference originates is one of the open questions in the study of life’s origins.
Why Was Erythrulose More Abundant Than Simpler Sugars?
One of the study’s unexpected findings was that erythrulose appeared to be at least eight times more abundant than comparable three-carbon sugar compounds, none of which were detected in the same molecular cloud despite the survey’s sensitivity. That result contradicts the standard model in astrochemistry, which predicts that larger molecules generally build up gradually through the sequential addition of single carbon atoms to smaller precursors.
Working with chemists from the University of Extremadura in Spain and Radboud University in the Netherlands, the research team demonstrated through laboratory experiments and astrochemical modeling that erythrulose can form directly within frozen interstellar ices through reactions involving simpler two-carbon alcohols and aldehydes. Ice-coated dust grains inside molecular clouds serve as natural chemical laboratories, where cosmic radiation and extremely low temperatures drive reactions that would not occur in other environments. The modeling showed that erythrulose forms efficiently under a range of cosmic-ray ionization rates, including conditions expected in the dust traps of protoplanetary disks — the rotating disks of material from which planets eventually emerge.
What Does This Mean for Understanding Life’s Origins?
The discovery creates a direct chemical pathway from interstellar space to the molecules that underpin biology. Previous prebiotic chemistry experiments have shown that ribonucleotides — the building blocks of RNA — can be synthesized from mixtures containing sugars such as erythrulose. If erythrulose forms efficiently on interstellar dust grains and is later incorporated into planetesimals, asteroids, and meteorites, it could have been delivered to early Earth as part of the organic inventory that seeded the planet’s prebiotic chemistry.
The detection of a chiral sugar in interstellar space also supports the hypothesis that the small asymmetries in molecular handedness measured in meteorites may originate in extraterrestrial environments rather than on Earth itself. Those small imbalances, potentially amplified through subsequent chemical processes, could have contributed to the emergence of the biological homochirality — the consistent handedness of amino acids and sugars — that characterizes all known life.
Jiménez-Serra noted that the finding “takes us to a higher level in the ladder of interstellar chemical complexity,” suggesting that other prebiotic molecules — and potentially other chiral compounds — could also form and survive under the extreme conditions of interstellar space. The molecular cloud G+0.693−0.027, which has become one of the richest known repositories of complex organic molecules in the galaxy, will likely remain a focal point for future surveys targeting the next tier of biological building blocks.
FAQs
What is erythrulose? Erythrulose is a four-carbon ketose sugar, meaning it belongs to the same chemical family as sugars like ribose (found in RNA) and glucose. On Earth, erythrulose occurs naturally in raspberries, kiwis, and other red fruits and is also used commercially in sunless tanning products.
Where was the sugar molecule detected? Erythrulose was detected in molecular cloud G+0.693−0.027, a dense region of gas and dust located near the center of the Milky Way galaxy, approximately 26,745 light-years from Earth. Molecular clouds are pre-stellar environments where no stars or planets have yet formed.
Has sugar been found in space before? Sugars had previously been detected in asteroid and meteorite samples — including NASA’s OSIRIS-REx samples from the asteroid Bennu — but erythrulose is the first sugar directly observed in interstellar space, the vast medium between star systems.
How was the detection made? Astronomers used the Yebes 40-meter and IRAM 30-meter radio telescopes in Spain to analyze spectral emissions from the molecular cloud. They identified 12 independent spectral lines matching erythrulose’s laboratory-measured signature.
Why does this matter for the origins of life? Sugars form the structural backbone of DNA and RNA and are essential for cellular metabolism. Finding sugar in a pre-stellar environment means life’s chemical building blocks can assemble before planets form, potentially seeding young worlds through asteroid and meteorite delivery.
What journal published the research? The study was published on July 13, 2026, in Nature Astronomy, a peer-reviewed journal from the Nature Research family. The research was led by Izaskun Jiménez-Serra of the Spanish National Research Council.
