Astronomers have made the first direct detection of a sugar molecule in the interstellar medium, a finding that sharpens understanding of how the chemical precursors to life might arise far from any planet.
The discovery centres on erythrulose, a simple four-carbon ketose sugar also known in terrestrial raspberries. It was spotted in the molecular cloud G+0.693-0.027, located near the centre of the Milky Way. The observation rests on rigorous radio astronomy data matched against laboratory spectra, published in Nature Astronomy on 13 July 2026.
Twelve spectral lines observed matched the laboratory spectrum of erythrulose. The detection was achieved using two Spanish instruments: the Yebes 40-metre radio telescope and the IRAM 30-metre radio telescope. Lead researcher Dr Izaskun Jiménez-Serra of the Centre for Astrobiology in Spain described the result as unexpected.
This finding was unexpected, as the prevailing view in astrochemistry is that interstellar molecules grow in size through the sequential addition of carbon atoms.
Instead, erythrulose appears to form on the surface of interstellar dust grains at temperatures around minus 250 degrees Celsius. The process involves reactions between two-carbon molecules such as glycolaldehyde and ethylene glycol. This grain-surface route at extremely low temperatures challenges earlier models and suggests complexity can emerge even without the warmth of stellar nurseries.
The abundance of erythrulose in the cloud is roughly eight to seventeen times higher than that of any three-carbon sugars, which were not detected there. Erythulose is only the second chiral molecule identified in interstellar space, a property that matters because chirality, or handedness, plays a central role in terrestrial biochemistry.
Models indicate that between 0.5 and 50 million metric tonnes of erythrulose could have reached early Earth during the Late Heavy Bombardment, the period between 4.1 and 3.8 billion years ago when comet and asteroid impacts were frequent. Such delivery would have added to the planet's inventory of prebiotic molecules at a time when life was taking shape.
