First True Sugar Molecule Found in Space Offers Fresh Clues to Life’s Origins
Date: 2026-07-14
Featured image: [Artist’s impression of a molecular cloud rich in organic molecules near the center of the Milky Way; credit: NASA/JPL-Caltech]
Astronomers have detected a true sugar molecule in interstellar space for the first time, identifying erythrulose in a dense molecular cloud roughly 26,000 light-years from Earth and opening a new window onto how the building blocks of life may form before planets are born.
The discovery, published July 13 in Nature Astronomy by a team led by Izaskun Jimenez-Serra of the Spanish National Research Council (CAB/CSIC), marks the largest non-cyclic molecule ever found in the interstellar medium. Erythrulose (C4H8O4) has four carbon atoms and 14 atoms total, making it the first molecule with four oxygen atoms detected beyond the Solar System and the second chiral molecule found in space.
“This finding was unexpected, as the prevailing view in astrochemistry is that interstellar molecules grow in size through the sequential addition of carbon atoms,” Jimenez-Serra said.
A Sweet Milestone
Previous detections of “sugars” in space had been limited to glycolaldehyde, a two-carbon hydroxyaldehyde first identified in 2000. While chemically related to sugars, glycolaldehyde lacks the three-carbon backbone that defines a true saccharide. Erythrulose crosses that threshold decisively.
The detection came from an ultrasensitive broadband spectral survey spanning more than 91 gigahertz across three atmospheric windows. Using the Yebes 40-meter radio telescope and the IRAM 30-meter telescope, both in Spain, the team identified 12 sets of spectral lines (17 individual transitions) that matched erythrulose’s rotational fingerprint.
That fingerprint came from a crucial laboratory breakthrough. In 2022, Emilio Cocinero at the University of the Basque Country developed an ultrafast laser vaporization technique to obtain erythrulose’s gas-phase rotational spectrum, mixing the syrupy sugar with talcum powder to overcome its notoriously sticky nature. He shared the data with Jimenez-Serra, who checked existing observations of the molecular cloud G+0.693-0.027 in the Central Molecular Zone near the galactic center. The match was immediate.
Why Erythrulose Matters
Sugars are essential to life as we know them. Ribose forms the backbone of RNA, deoxyribose of DNA. How these molecules first appeared on early Earth has been a long-standing puzzle. Laboratory simulations of prebiotic chemistry produce sugars only in vanishingly small concentrations.
Finding erythrulose in an interstellar gas cloud shifts the picture. Ribose and glucose had previously been found inside meteorites and in samples from asteroid Bennu, but those could have formed after the parent bodies accreted. A detection in the gas phase shows that sugars assemble before any solid body forms, in the cold, dense clouds that give birth to stars and planets.
Based on erythrulose’s abundance in G+0.693-0.027, the team estimates that between 500,000 and 50 million metric tons of the molecule could have rained onto Earth’s surface during the Late Heavy Bombardment around 4.1 to 3.8 billion years ago, providing a direct exogenous supply of prebiotic sugar.
“This is an incredibly exciting result,” said Brett McGuire, an MIT astrochemist not involved in the study. “Astronomers have, for a very long time, been pushing to detect sugars in space.”
An Unexpected Chemistry
The discovery also challenges assumptions about how complex molecules grow in space. Three-carbon sugars such as glyceraldehyde and dihydroxyacetone were expected to be more abundant through sequential carbon addition, but they were not detected. Erythrulose is 8 to 17 times more abundant than predicted, suggesting it forms through a different pathway: the combination of two two-carbon molecules (glycolaldehyde and ethylene glycol) on the surface of icy dust grains.
Erythrulose is also a direct chemical precursor to threose nucleic acid (TNA), a leading candidate for the genetic polymer that may have preceded RNA and DNA in the earliest forms of life. The detection therefore touches not just the question of where sugars come from, but which molecular path life itself took at its origin.
“The detection of erythrulose is very exciting because it opens up the possibility of discovering in space other sugars such as ribose, which is part of RNA, and other important molecules for the origin of life,” said co-author Carlos Briones.
On Earth, erythrulose occurs naturally in raspberries, kiwis, and red fruits, and is widely used in sunless tanning products. In space, it is now a key piece in the puzzle of how the raw ingredients for life assemble before any planet exists.