Astronomers have detected erythrulose, a sugar found in raspberries and self-tanning products, in interstellar space near the Milky Way’s center, marking the first direct identification of a true sugar in the interstellar medium and offering new clues about life’s chemical origins.
The discovery, published Monday in *Nature Astronomy*, reveals that a four-carbon sugar called erythrulose exists in the molecular cloud G+0.693−0.027, located 8.2 kiloparsecs from Earth. This finding challenges long-held assumptions about how interstellar molecules form and suggests that life’s building blocks may have originated in space. The research, led by Izaskun Jiménez-Serra of Spain’s Center for Astrobiology, used radio telescopes in Yebes and IRAM to detect the sugar’s spectral signature, matching it to laboratory measurements.
A Sweet Twist in Cosmic Chemistry
For decades, scientists assumed that interstellar molecules grow incrementally, adding carbon atoms one by one. But the detection of erythrulose defies this pattern. Jiménez-Serra’s team found that four-carbon erythrulose was at least eight to 17 times more abundant than three-carbon sugars, which were entirely absent in the cloud. This contradicts astrochemical models, which predict that larger molecules should be rarer. “This finding was unexpected, as the prevailing view in astrochemistry is that interstellar molecules grow in size through the sequential addition of carbon atoms,” Jiménez-Serra said.
The team proposed a mechanism for erythrulose’s formation: two-carbon molecules—glycolaldehyde and ethylene glycol—react on icy dust grains in the cloud. Computer simulations showed that erythrulose could form efficiently under these conditions, suggesting it might have been synthesized before stars and planets existed. The sugar’s structure, with 14 atoms and a ketone group, makes it the largest non-cyclic molecule detected in interstellar space.
Implications for Life’s Origins
Erythrulose’s discovery strengthens the hypothesis that life’s essential ingredients were delivered to Earth via asteroids and comets. Previous studies have found sugars like ribose in meteorites and samples from the asteroid Bennu, but this is the first time a true sugar has been detected in the interstellar medium. “It opens the possibility for life to develop on other worlds in a similar fashion to what it did in on Earth,” Jiménez-Serra said.
For more on this story, see Scientists Detect Erythrulose, Rare Sugar, in Interstellar Space.
Scientists estimate that between 0.5 million and 50 million metric tons of erythrulose may have rained down on Earth during the Late Heavy Bombardment, a period of intense asteroid impacts 4 billion years ago. While the sugar itself is not essential for life, it can react to form ribonucleotides, the building blocks of what was probably the first genetic material, RNA. This suggests that interstellar chemistry may have provided the raw materials for early metabolic processes.
The discovery also highlights the role of chirality in biology. Erythrulose is the second chiral molecule detected in the interstellar medium, meaning it exists in mirror-image forms. This property is critical for life, as biological systems require specific molecular orientations.
A New Era in Astrochemistry
While erythrulose was detected in one cloud, researchers believe similar compounds may exist in other molecular clouds where stars and planets form. If these life-related molecules are widespread, the same chemical processes that helped prepare Earth for life could be occurring elsewhere in the universe, said study coauthor Carlos Briones.
Further research will focus on identifying other sugars and understanding how they evolve in space. The team plans to use more sensitive instruments to probe deeper into interstellar chemistry. “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,” Briones said.
The discovery underscores the interconnectedness of cosmic and terrestrial chemistry. As scientists continue to unravel the origins of life, erythrulose’s presence in the Milky Way’s heart offers a glimpse into the universal processes that may have shaped biology on Earth and beyond.
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