Sugars are essential biomolecules, serving as metabolic fuels and the structural backbone of nucleic acids (DNA and RNA). A central question in origin-of-life research is: how did these substances appear on the primitive Earth? A recent discovery by an international team of scientists provides a staggering answer — they were forged in deep space.
A Historic Find in the Galactic Center
While scientists have previously found sugars like ribose and glucose in meteorites and asteroids, they had never been observed directly in the interstellar medium (ISM). This changed thanks to the ultrasensitive Yebes 40m and IRAM 30m radio telescopes.
Scanning the molecular cloud G+0.693−0.027, located near the center of our Galaxy (about 26,000 light-years away), researchers detected the spectral signatures of erythrulose. This is a complex chiral four-carbon sugar. Comprising 14 atoms, erythrulose has become the largest non-cyclic molecule—and the first containing four oxygen atoms—ever found in the ISM.
A Factory on Icy Dust Grains
How could such a complex molecule form in the cosmic cold at temperatures around 20 Kelvin (-250 °C)? Quantum chemical and astrochemical models show that erythrulose synthesizes efficiently on the surface of interstellar dust grains covered in ice.
It is formed by the merging of simpler two-carbon molecules—radicals of glycolaldehyde and ethylene glycol—which are abundantly present in the G+0.693 cloud. Through this process, driven by cosmic rays, a sugar is born, ready to become a building block for life.
Building Blocks of the First RNAs
The discovery of erythrulose is of colossal importance for astrobiology. In the aqueous environment of the primitive Earth, such ketoses could readily isomerize into aldoses (like threose), which are critical for the formation of primitive nucleic acids.
Researchers estimate that during the Late Heavy Bombardment (about 4 billion years ago), comets and meteorites could have delivered anywhere from 500 million to 50 billion kilograms of this cosmic sugar to the young Earth.
Bottom Line: The detection of interstellar erythrulose proves that space is an active chemical factory. The ISM could have been a viable and reliable source of sugar feedstock for the prebiotic synthesis of the first nucleic acids — not only on Earth but potentially elsewhere in the Universe.
Source: Published in Nature Astronomy. Read the original paper at Nature.com.
