Interstellar Sugar Detected: Erythrulose Found 26,000 Light-Years Away — A New Clue To Life’s Origins

Scientists have identified a four-carbon sugar, erythrulose (C4H8O4), in a distant molecular cloud — a discovery that could reshape ideas about how the raw ingredients for life were supplied to the early Earth.

Life depends on a handful of basic elements and organic molecules, and sugars are especially important because they form the backbone of RNA and DNA. How those sugars first appeared on the primitive Earth has been debated for decades. The dominant hypothesis has been delivery by comets and meteorites; in 2023 researchers reported sugar-related compounds on the asteroid Bennu as part of NASA’s OSIRIS-REx mission.

Now, a team publishing in Nature Astronomy reports the first direct detection of a sugar molecule beyond our solar system. Using sensitive radio telescopes in Spain — the Yebes Observatory and the IRAM 30-meter telescope — they detected spectral signatures of erythrulose in the cold gas of a molecular cloud labeled G+0.693−0.027. This cloud lies within the Sagittarius B2 complex, about 26,000 light-years from Earth and roughly 390 light-years from the Galactic Center.

How the Detection Was Made

Cold molecular clouds like G+0.693 are excellent laboratories for astrochemistry. Icy molecules that form on dust grains can sublimate into the gas phase at low temperatures and produce characteristic radio-frequency emission lines. By matching those lines with laboratory spectra, astronomers can identify complex organic molecules remotely. G+0.693 is one of the most molecule-rich regions known: scientists have identified on the order of 340 molecular species there.

Why This Matters

The finding is surprising for two reasons. First, sugars have not previously been directly observed in the interstellar medium (ISM). Second, instead of finding a simpler three-carbon sugar, the team detected a more complex four-carbon sugar. As MIT scientist Brett McGuire put it, scientists “skipped all the three-carbon sugars and went straight to four carbons,” a result the team describes as astonishing.

“A central question in origin-of-life research is how monosaccharides formed on the primitive Earth, as laboratory experiments under prebiotic conditions yield insufficient concentrations,” the study notes. “The discovery of interstellar erythrulose suggests that the ISM could be a viable source of sugar feedstock for the prebiotic synthesis of the first nucleic acids, not only on the primitive Earth but also elsewhere in the Universe.”

Using estimates of water content in meteorites and models of material delivery to the young Earth, the researchers calculate that between 0.5 and 50 billion kilograms of erythrulose could have been deposited on our planet during the Late Heavy Bombardment about four billion years ago. If so, interstellar sugars may have supplemented terrestrial chemistry and helped kick-start the formation of early nucleic acids.

“The key ingredients for the origin of life could be present in other regions across the galaxy,” said Izaskun Jiménez-Serra of Spain’s Center for Astrobiology, highlighting the broader astrobiological implications reported to the Associated Press.

Beyond astrobiology, the discovery strengthens evidence that complex organic molecules can form on icy dust grains in space and later be released into the gas phase, increasing the chemical inventory available to young planets. Erythrulose — a compound also found in raspberries on Earth — now joins a growing catalog of interstellar organics and invites further study of how prebiotic chemistry operates on cosmic scales.