Astronomers detect first true sugar in interstellar space

An international team of astronomers has identified the first true sugar molecule ever found in the space between stars — a discovery that strengthens the case that life's chemical building blocks are scattered throughout the galaxy.

The molecule, called erythrulose, is a four-carbon sugar also found in raspberries and commonly used in self-tanning products. Researchers detected it in a giant molecular cloud known as G+0.693-0.027, located near the center of the Milky Way, according to a study published Monday in Nature Astronomy.nature+1

How the Discovery Was Made

The team, led by Izaskun Jiménez-Serra of Spain's Centro de Astrobiología, used two powerful radio telescopes — the 40-meter Yebes telescope in Spain and the 30-meter IRAM telescope — to sift through the cloud's dense spectral lines. The detection confidence was high, with the probability of the spectral signature appearing by chance amounting to just 0.2 percent.eurekalert+1

Intriguingly, the researchers found no three-carbon sugars in the cloud. Erythrulose was at least eight times more abundant than three-carbon analogs such as glyceraldehyde. Using quantum chemical models and Kinetic Monte Carlo simulations, the team determined that erythrulose likely forms when two-carbon fragments — glycolaldehyde and ethylene glycol — combine on the icy surfaces of microscopic dust grains bombarded by cosmic rays.universetoday+1

Why It Matters for the Search for Life

The discovery carries implications for understanding how life began on Earth and possibly elsewhere. Modern DNA and RNA rely on ribose, a five-carbon sugar, as their structural backbone. But ribose is difficult to produce under early-Earth conditions. Astrobiologists have long hypothesized that a simpler precursor polymer may have preceded DNA and RNA.universetoday

A leading candidate is Threose Nucleic Acid, which uses a four-carbon sugar called threose. In the presence of liquid water, ketose sugars like erythrulose can readily convert into aldose sugars like threose — meaning the molecule found in this interstellar cloud provides a direct chemical pathway to a possible precursor of genetic material.universetoday

Scientists already know that large quantities of complex organic molecules were delivered to early Earth during the Late Heavy Bombardment, when the planet was pelted by space debris. The new finding suggests that by the time Earth's oceans cooled enough to support chemistry, sugars like erythrulose may have already been available to participate in prebiotic reactions.universetoday

A New Chapter in Astrochemistry

While simpler sugar-related molecules like glycolaldehyde had previously been found in space, erythrulose represents the first detection of a complete monosaccharide — a true sugar — in the interstellar medium. The molecular cloud G+0.693-0.027 has become something of a treasure trove for astrochemists, yielding more than 20 first-time molecular detections in recent years.gizmodo+2

The study's authors note some uncertainties, including a lower-than-expected detection rate compared to their simulations, suggesting further observations are needed. But the central finding stands: the chemical precursors to life's genetic machinery are being actively assembled in the vast spaces between the stars.universetoday