Deep in the heart of our galaxy, scientists have spotted something sweet — the first sugar ever found floating in interstellar space. The discovery, published in the journal Nature Astronomy, could help explain how life first sparked on Earth billions of years ago.
The sugar is called erythrulose, and it's a simple four-carbon molecule you might already know from everyday life. It's what gives raspberries their subtle sweetness, and it's even used in sunless tanning lotions to give skin a golden glow. But finding it drifting in the cold void between stars? That's something entirely new.
An international team led by Izaskun Jiménez-Serra, a researcher at the Center for Astrobiology (CAB) in Spain, spotted the molecule hiding inside a giant cloud of gas and dust near the center of the Milky Way. The cloud, called G+0.693−0.027, sits about 26,000 light-years from Earth — relatively close, in cosmic terms.
The detection required incredibly sensitive instruments. The team used two powerful radio telescopes: the 40-meter Yebes radio telescope in Spain and the 30-meter telescope operated by IRAM, the Institute for Radio Astronomy in the Millimeter Range, based in Grenoble, France. These telescopes act like giant ears, picking up faint radio signals given off by molecules in space. The scientists matched 12 different radio signals from the cloud to the known fingerprint of erythrulose, measured in a laboratory at the University of the Basque Country.
What's especially surprising is how abundant the sugar appears to be. Erythrulose showed up at levels at least eight times higher than similar three-carbon sugars, which the team couldn't detect at all in the same cloud. That was unexpected, since the standard view in astrochemistry — the study of chemicals in space — holds that molecules tend to grow by adding one carbon atom at a time, step by step.
So where did all this sugar come from? The research suggests erythrulose can form directly inside interstellar ices from simpler two-carbon building blocks, like alcohols and aldehydes. This sidesteps the usual step-by-step process and could mean sugars are more common in space than scientists once thought.
That matters for understanding life's origins. During a period called the Late Heavy Bombardment, roughly 4.1 to 3.8 billion years ago, a rain of asteroids and comets pummeled the young Earth. Based on how much erythrulose the researchers found in the cloud, they calculate that between half a million and 50 million metric tons of this sugar could have arrived on our planet during that chaotic time. That's the weight of roughly 100,000 to 10 million African elephants, delivered by space rocks.
Sugars are crucial for life as we know it. They form the structural backbone of DNA and RNA — the molecules that carry our genetic code — and fuel our cells through metabolism. Figuring out where they came from is a major piece of the puzzle of how life began.
"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.
In other words, this first sweet discovery may just be the beginning.