The asteroid Bennu is providing scientists with critical insights into the early solar system and the origins of life. NASA’s OSIRIS-REx mission successfully returned pristine samples to Earth, enabling unprecedented analysis. Recent studies published in Nature Geosciences and Nature Astronomy highlight three groundbreaking discoveries. Researchers identified sugars essential for life, including ribose and glucose, which are key to RNA and energy production. They also discovered a previously unknown gum-like polymer rich in nitrogen and oxygen, offering clues to the chemical precursors of life. Additionally, Bennu’s samples contain an unusually high concentration of dust from ancient supernovae, revealing the asteroid’s formation environment and the distribution of presolar materials in the early solar system. These findings deepen our understanding of life’s cosmic origins.
Discovery of life-essential sugars in Bennu asteroid samples
A team of researchers led by Yoshihiro Furukawa of Tohoku University in Japan identified biologically important sugars in the Bennu samples, as reported in Nature Geosciences. Among the findings were the five-carbon sugar ribose and, for the first time in an extraterrestrial sample, six-carbon glucose. While these sugars are not evidence of life themselves, their presence, along with previously discovered amino acids, nucleobases, and carboxylic acids, indicates that the building blocks of biological molecules were widespread in the early solar system.Furukawa emphasised the significance of this discovery: “All five nucleobases used to construct DNA and RNA, along with phosphates, have already been found in the Bennu samples. The new discovery of ribose means that all the components to form RNA are present in Bennu.” Interestingly, deoxyribose was not detected in Bennu. This suggests that ribose may have been more common in the early solar system, supporting the “RNA world” hypothesis, which proposes that life’s first molecules relied on RNA for both information storage and biochemical reactions.In addition to ribose, researchers also discovered glucose, a critical energy source for life on Earth. Its presence in Bennu samples provides the first evidence that essential sugars for energy and structural purposes were available in the early solar system, possibly delivered to Earth by meteorites.
Discovery of a mysterious gum-like substance
A second study led by Scott Sandford of NASA’s Ames Research Center and Zack Gainsforth from the University of California, Berkeley, identified an unusual gum-like material in Bennu samples, reported in Nature Astronomy. This organic material, never observed before in space rocks, likely formed during the early heating of Bennu’s parent asteroid and may have contributed to the chemical precursors necessary for life on Earth.This ancient “space gum” is composed of nitrogen- and oxygen-rich polymer-like compounds that were once soft and flexible but have since hardened over billions of years. These complex molecules may have formed before the asteroid developed a watery environment, giving scientists a glimpse into the earliest chemical alterations in the solar system.Sandford explained the significance of the discovery: “On this primitive asteroid that formed in the early days of the solar system, we’re looking at events near the beginning of the beginning. These findings help us understand the chemical processes that may have contributed to the emergence of life on Earth.”
Abundance of supernova dust reveals asteroid origins
The third paper, led by Ann Nguyen of NASA’s Johnson Space Center, focused on presolar grains within Bennu samples, which are tiny dust particles formed in stars before the solar system existed. The analysis revealed that Bennu contains six times more supernova-derived dust than any previously studied astromaterial. This suggests that Bennu’s parent asteroid formed in a region of the early solar system enriched with material from dying stars.Despite undergoing significant alteration by fluids over billions of years, some of Bennu’s material remained largely unchanged, preserving presolar silicate grains and organic matter. These preserved grains offer vital insights into the asteroid’s formation, its geologic history, and the diversity of materials in the early solar system.Nguyen commented, “These fragments retain a higher abundance of organic matter and presolar grains that would normally be destroyed by aqueous alteration. Their preservation allows us to study the building blocks of the solar system and understand the diversity of presolar materials accreted during formation.”
