Scientists Detect a True Sugar in Deep Space for the First Time

A Sweet Discovery at the Heart of the Galaxy

Erythrulose, a sugar found in raspberries, kiwis, and many red fruits, apparently exists in a giant molecular cloud of gas and dust near the center of our galaxy, some 26,745 light-years from Earth. This marks the first time a sugar has been seen in interstellar space. The finding, published Monday, July 13 in the journal Nature Astronomy, is turning heads across the scientific world — and raising a profound question about how life on Earth got its start.

Erythrulose, with 14 atoms in its structure, represents the largest non-cyclic molecular species identified so far in the interstellar medium, and the first detected molecule containing four oxygen atoms. Astronomers have long been pushing to detect sugars in space, and erythrulose — with its four carbon atoms — is the most complex sugar spotted beyond our Solar System.

How Scientists Found It

Using the Yebes 40-m and IRAM 30-m radio telescopes, the astronomers scanned the molecular cloud G+0.693−0.027, a chemically rich region located roughly 8,200 parsecs from Earth near the Milky Way's center. At the cloud's low temperatures, molecules rotate and emit radio waves at characteristic frequencies that act as molecular fingerprints. By comparing observations with laboratory measurements of erythrulose's rotational spectrum, the team identified multiple matching spectral lines consistent with the sugar.

The team identified 12 spectral lines matching the laboratory spectrum of erythrulose measured at the University of the Basque Country. The study also shows that this sugar is at least eight times more abundant than similar three-carbon sugars, none of which were detected in the same region. That last detail surprised researchers. They were expecting that simpler sugars containing three carbon atoms would dominate. Instead, four-carbon erythrulose appeared to be at least 8 to 17 times more abundant than the three-carbon sugars glyceraldehyde and dihydroxyacetone, which weren't detected in the cloud at all.

Why It Matters for the Origin of Life

Sugars are essential to life, forming the backbone of DNA and RNA and serving as metabolic fuel, but scientists have long struggled to explain how they could have formed in sufficient quantities on the early Earth. Lab experiments simulating prebiotic conditions tend to produce sugars only in trace amounts. The discovery of erythrulose in deep space offers a compelling alternative explanation for where those sugars may have come from.

Researchers detected erythrulose, a four-carbon monosaccharide that could have been transferred to minor bodies, such as comets and asteroids, and then delivered to younger planets such as the early Earth. Based on the abundance of erythrulose measured in the molecular cloud, researchers estimate that between 0.5 and 50 million tonnes of this sugar could have reached Earth's surface during the Late Heavy Bombardment, which occurred approximately 4.1 to 3.8 billion years ago.

A Doorway to Even Bigger Discoveries

Although astronomers have previously detected nearly 30 molecules linked to prebiotic chemistry, this study reports the first true sugar identified in interstellar space. The discovery of erythrulose suggests that complex sugars can form on icy dust grains long before planets emerge. The detection of ribose and glucose in meteorites and in samples from the asteroid Bennu has already fueled speculation that at least some of Earth's sugar inventory may have arrived from space — and this new find adds powerful weight to that idea.

"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," says Carlos Briones, co-author of the study. Ribose is the sugar that forms the backbone of RNA, widely considered a critical molecule in the earliest stages of life. If ribose can also be found drifting through interstellar clouds, it would dramatically strengthen the case that the cosmos itself helped seed Earth with the chemistry needed for life to arise.