Spanish-led team detects sugar in interstellar space for the first time, revealing ingredients for life form before stars exist

A team led by the Center for Astrobiology (CAB, CSIC-INTA) in Torrejón de Ardoz has reported the first direct detection of a sugar molecule freely floating in the interstellar medium. The discovery, published on 13 July 2026 in Nature Astronomy, identifies erythrulose in the molecular cloud G+0.693-0.027 near the centre of the Milky Way. Previous searches had found sugars like ribose and glucose inside meteorites and the asteroid Bennu, but never in the diffuse gas and dust between stars. The work involved researchers from Spain, the Netherlands, Italy, Germany, and the United States.

First sugar in the interstellar medium

Sugars are the structural backbone of RNA and DNA, yet laboratory experiments that try to recreate the origin of life on early Earth consistently produce them in amounts too small to be plausible. This paradox has pushed astrobiologists to look beyond Earth. The new detection resolves that tension: erythrulose, a simple four-carbon sugar, is present where stars and planets are born.

Sugars are essential organic compounds because they represent the backbone of RNA and DNA.

The cloud G+0.693-0.027 is among the richest molecular reservoirs known in the galaxy. Its chemical complexity has made it a natural laboratory for astrochemistry. Erythrulose is a ketose, the only four-carbon sugar with a chiral centre, and on Earth it occurs in raspberries and is used in self-tanning lotions. In the interstellar medium it demonstrates that sugars can form spontaneously long before a planetary system exists.

What is impressive is to discover that they can be synthesized so early, in nebulae where there are no stars or planetary systems yet formed.

How the detection was made

Observations combined the 40-metre radio telescope at Yebes (Guadalajara) and the 30-metre IRAM dish at Pico Veleta (Granada). The team first measured erythrulose's rotational spectrum in the laboratory, obtaining a precise chemical fingerprint. They then searched broadband spectral data from the cloud and identified 12 independent emission lines that matched the fingerprint.

The signals are unambiguous. The cloud lies roughly 27,000 light-years away and contains at least enough material to make the detection statistically robust. Jiménez-Serra notes that the team needed a region with a very high column density to amplify the faint molecular lines to detectable levels.

Abundance and chemistry

Erythrulose is strikingly abundant relative to similar molecules. In G+0.693-0.027 it is at least eight times more plentiful than structurally comparable three-carbon sugars, which are conspicuously absent. This pattern suggests that at the cloud's low temperatures sugars are assembled step by step on the surfaces of dust grains, gradually building complexity.

From a prebiotic standpoint, erythrulose is not a dead end. In aqueous environments it converts into threose, a component of threose nucleic acid (TNA), a possible evolutionary precursor of RNA.

This sugar specifically has the ability to react in aqueous media to give more complex structures and originate polymers.

The co-author adds that the discovery opens the door to the existence of five-carbon sugars like ribose in the same environment, strengthening the RNA-world hypothesis for the origin of life.

From the cloud to early Earth

The team estimates that during the late heavy bombardment, around 4 billion years ago, Earth received between 0.5 and 50 million tonnes of erythrulose from asteroids and comets that condensed out of such molecular clouds. This delivery mechanism provides enough material to seed the chemistry that eventually produced the first nucleic acids.

We estimated that Earth could have received between 0.5 and 50 million tonnes of erythrulose during the last intense bombardment of large asteroids. It is one of the periods where the most organic material could have arrived, and it is said to be crucial because life emerged very shortly after.

What comes next

The search now expands to other molecular clouds and to larger sugars. The same spectral methods can be aimed at ribose and glucose, whose interstellar existence is strongly hinted at by meteorite studies. Jiménez-Serra's group plans further observations with the same and additional facilities, hoping to map the full sugar inventory of the interstellar medium and trace the chemical pathway from simple molecules to the building blocks of life.