Astronomers have detected erythrulose, a natural sugar found in raspberries and used in fake tan lotions, in an enormous cloud of dust and gas near the centre of the Milky Way. The discovery, published in Nature Astronomy, marks the first time a sugar has been directly observed in interstellar space, suggesting that compounds essential for life can form in the frigid expanse between stars.
Discovery Details
Dr Izaskun Jiménez-Serra at Spain's Centre for Astrobiology and her colleagues used two Spanish radio telescopes to observe the dust cloud G+0.693-0.027. After finding no trace of three-carbon sugars, they were not hopeful, but then spotted the signature of erythrulose, a four-carbon sugar. "To my surprise, I saw the signals," Jiménez-Serra said.
Erythrulose appears to form through chemical reactions on tiny interstellar dust grains, where two other organic compounds—glycolaldehyde and ethylene glycol—combine despite temperatures around -250°C. These grains can then rain down on nearby worlds or reach them after being incorporated into comets that eventually crash into planets.
Implications for Life
Simple sugars like erythrulose can react to form ribonucleotides, the building blocks of RNA, which was likely the first genetic material. As early life evolved, DNA arose as a more robust store for genetic code. 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."
Prof Yoshihiro Furukawa at Tohoku University, 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."
Erythrulose on Earth
Erythrulose is found in trace amounts in red raspberries and is used in fake tan lotions, where it reacts with amino acids in dead skin cells to create brown polymers called melanoidins through the Maillard reaction—the same process that gives steak its dark crust.
