Essential sugars, ‘Gum’ & stardust-what new NASA study reveals about life’s cosmic origins
Researchers say this ancient “space gum,” once soft and flexible but now hardened, may have provided some of the chemical precursors needed for life to emerge on Earth.
New Delhi: It took 4.5 billion years for a few grams of an ancient asteroid to reach a laboratory on Earth, and with it, chemical clues to our beginnings. Bennu, a relic from the solar system’s infancy, has emerged as a molecular time capsule. Its dust holds essential sugars, a strange gum-like polymer and ancient stardust forged in dying stars, hinting that the chemistry that seeded life on Earth may have been circulating through the young solar system from the very start.
In 2020, NASA’s OSIRIS-REx mission touched the surface of Bennu, orbiting between Mars and Jupiter. The mission returned with samples to Earth in 2023.
“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,” says Scott Sandford, astrophysicist at NASA’s Ames Research Center.
Papers published Tuesday by the journals Nature Geoscience and Nature Astronomy prove the presence of essential sugars, gum-like substances and stardust in the asteroid samples.
Essential sugars for life on Earth
A team of scientists led by Yoshihiro Furukawa of Tohoku University in Japan has found five-carbon sugar ribose and six-carbon glucose in the dust and rock that NASA brought back from Bennu. This is the first time that essential sugars have been found in an extraterrestrial sample.
However, the sugars by themselves may not be evidence of life beyond this planet, but their discovery, in addition to amino acids, nucleobases, and carboxylic acids in Bennu samples earlier, shows the widespread presence of biological molecules in the solar system.
Ribose is a crucial component of RNA, while deoxyribose forms part of DNA. Although ribose has previously been detected in meteorites, the Bennu samples did not contain deoxyribose. Researchers say this supports the “RNA world” hypothesis, in which early life relied on RNA to store genetic information and drive basic chemical reactions.
“Present-day life is based on a complex system organized primarily by three types of functional biopolymers: DNA, RNA, and proteins,” explains Furukawa. “However, early life may have been simpler.”
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Primitive ‘gum’
A gum-like substance — soft, flexible — has been identified in Bennu samples in a study published in Nature Astronomy. Scientists say that a soft-plastic-like substance has not been seen before in space rocks.
A team, led by Scott Sandford of NASA’s Ames Research Center and Zack Gainsforth of UC Berkeley, has found this polymer-like substance to be extremely rich in nitrogen and oxygen, formed very early in the solar system as Bennu’s parent asteroid slowly warmed.
Researchers say this ancient “space gum,” once soft and flexible but now hardened, may have provided some of the chemical precursors needed for life to emerge on Earth. Its presence in Bennu’s pristine material offers new clues to how complex molecules formed long before the solar system matured.
“We knew instantly we had something remarkable,” Gainsforth said. “It was like nothing we had ever seen.”
Stardust
Another study in Nature Astronomy, led by Ann Nguyen of NASA’s Johnson Space Center, turned its focus to some of the oldest material found in space: presolar grains. These are the tiny dust particles forged in stars that died long before the solar system existed. Nguyen’s team identified these ancient grains in two different rock types within the Bennu samples, using them to trace where the asteroid’s parent body formed and how it later evolved.
The study also found that, although Bennu’s parent asteroid saw extensive alteration by water-rich fluids, not everything was reworked. Tucked inside the samples were tiny pockets of material that remained untouched.
“These fragments retain a higher abundance of organic matter and presolar silicate grains, which are known to be easily destroyed by aqueous alteration in asteroids,” Nguyen said. “Their preservation in the Bennu samples was a surprise and illustrates that some material escaped alteration in the parent body.”
(Edited by Saptak Datta)
