Astronomers have detected a natural sugar called erythrulose in a massive cloud of dust and gas near the center of the Milky Way.
This compound, also found in raspberries and used in fake tan lotions, is the first sugar ever identified in interstellar space.
The discovery indicates that molecules crucial for life can form in the frigid expanse between stars.
Erythrulose appears to be produced through chemical reactions on tiny interstellar dust grains, which then rain down on nearby planets or reach them via comets.
“This is the very first sugar to be detected in interstellar space and it is important because it tells us that these sugars are more common than we previously thought,” said Dr. Izaskun Jiménez-Serra at Spain’s Centre for Astrobiology near Madrid.
“It opens the possibility for life to develop on other worlds in a similar fashion to what it did on Earth.”
Scientists have long puzzled over how simple sugars became abundant on Earth, as lab studies show they would not have formed easily on the young planet.
Jiménez-Serra and her team used two Spanish radio telescopes to observe a dust cloud called G+0.693-0.027 near the galactic center.
After finding no trace of three-carbon sugars, they were not optimistic about finding others. But then they spotted the signature of erythrulose, a four-carbon sugar.
“To my surprise, I saw the signals,” Jiménez-Serra said.
Writing in Nature Astronomy, the researchers describe how erythrulose can form when two other organic compounds—glycolaldehyde and ethylene glycol—combine on microscopic dust grains.
These reactions occur even though the temperature hovers around -250°C.
Simple sugars like erythrulose can react to form ribonucleotides, the building blocks of RNA, which is thought to have been the first genetic material.
The scientists estimate that millions of tonnes of erythrulose could have rained down on Earth during the Late Heavy Bombardment, a period of intense asteroid and comet impacts.
“To have suffered this kind of rain of organics, I think that seems to have been a key step,” Jiménez-Serra said.
“That material could have contributed to prebiotic soups where the first biomolecules were synthesised.”
Erythrulose reacts with amino acids in dead skin cells to create brown polymers called melanoidins through the Maillard reaction.
Prof. Yoshihiro Furukawa at Tohoku University in Japan, who discovered sugars in the Bennu asteroid, commented: “We have been waiting for an actual detection like this.
Sugars formed in the interstellar medium can reach Earth and other planets via cometary dust… This supply may have helped facilitate the emergence of life, if planetary environments were able to build life from such molecules, although that process itself remains unclear.”
