Samples from asteroid Bennu, collected by NASA's OSIRIS-REx mission, have revealed the presence of ribose and other sugars, completing the set of ingredients needed to kick-start life as known on Earth. This discovery confirms that asteroids like Bennu could have delivered all prerequisites for life to our planet or others. The findings support the idea that life-building molecules formed in briny environments on ancient asteroids.
NASA's OSIRIS-REx mission gathered 121 grams of material from Bennu in 2020, an asteroid orbiting between Mars and Jupiter, and returned it to Earth in 2023. Initial analyses identified water, carbon, organic molecules, amino acids, formaldehyde, the five nucleobases in RNA and DNA, and phosphates. However, the sugars forming the 'rungs' of RNA and DNA—ribose and deoxyribose—were absent from early studies.
Researchers led by Yoshihiro Furukawa at Tohoku University in Japan addressed this gap by processing a portion of the sample with acid and water, then analyzing it via gas chromatography-mass spectrometry. They detected ribose along with lyxose, xylose, arabinose, glucose, and galactose, but not deoxyribose. "This is a new finding of sugars in extraterrestrial materials," Furukawa said, noting that glucose plays a key role in the metabolism of nearly all life forms.
Sara Russell at the Natural History Museum in London, who studies Bennu samples but was not involved in this research, praised the result: "This is such a brilliant result from the OSIRIS-REx mission. The one missing ingredient was the sugar, which has now been reported, so now all of the ingredients of RNA are known to be in primitive asteroids."
The team suggests these sugars originated from formaldehyde in brines on Bennu's parent body, which likely hosted fluid reactions. Russell added context from earlier findings: "Earlier this year, we reported finding salts in the returned sample, and suggested there would have been briny pools of water on Bennu’s parent body. Such environments would have perfect places to cook up the complex organics that we see in Bennu."
Similar briny conditions appear on Saturn's moon Enceladus and dwarf planet Ceres, hinting at widespread life ingredients across the solar system. Furukawa's prior detection of sugars in Earth-found meteorites raised contamination concerns, but the pristine Bennu sample eliminates that doubt. The discovery bolsters the notion that asteroids supplied life's building blocks to Earth or Mars and aligns with the RNA world hypothesis, where early life relied on self-replicating RNA molecules before DNA or cells emerged.