Scientists discover sugars needed for life in asteroid samples for the first time

All the basic ingredients needed for life to start have now been found in samples from the asteroid Bennu. The study, published Dec. 2 in Nature Geoscience, suggests that asteroids may have delivered all the prerequisites for life to Earth — and perhaps elsewhere.

In 2020, NASA's OSIRIS-REx mission collected samples on Bennu. At that time, Bennu was orbiting between Mars and Jupiter, hundreds of millions of kilometers from the sun. The mission will return samples to Earth in 2023. A small amount of the 121 grams of samples collected was distributed to laboratories around the world for analysis so that experts in various fields can detect various biological compounds.

Initial studies revealed the presence of water, carbon, and a variety of organic molecules. The scientists then detected amino acids, formaldehyde, all five bases that make up RNA and DNA, and phosphates. However, these components are not enough to assemble molecules that carry genetic information. The "ladder" of RNA and DNA structures also contains a sugar: ribose in RNA, or deoxyribose in DNA, which had not been found in previous analyzes of Bennu samples.

In the latest study, Yoshihiro Furukawa of Tohoku University in Japan and colleagues crushed a small portion of the sample and mixed it with acid and water. They then used gas chromatography-mass spectrometry to separate and identify the components in the mixture. They found ribose, as well as a variety of other sugars, including lyxose, xylose, arabinose, glucose and galactose, but no deoxyribose.

"This is the first time that sugar has been found in alien matter." Furukawa said that almost all life depends on glucose in its metabolism.

Sara Russell from the Natural History Museum in London, UK, commented: "The OSIRIS-REx mission has achieved such outstanding results. The only missing ingredient before was sugar, and now this ingredient has been confirmed to be present, which means that all the components of RNA have been confirmed to be present in the primitive asteroid."

Furukawa and colleagues believe these sugars formed in the formaldehyde-rich brine contained in Bennu's parent asteroid. Scientists speculate that Bennu's parent asteroid once contained more liquid and experienced richer chemical reactions.

"Earlier this year, we reported the discovery of salts in returned samples and speculated that there may be salty pools on Bennu's parent body. Such an environment is an ideal place to synthesize the complex organic matter we see in Bennu," Russell said.

Russell also pointed out that there is also evidence of brine on Saturn's moon Enceladus and the dwarf planet Ceres, suggesting that the ingredients needed for life may be common throughout the solar system.

Furukawa has previously detected ribose and other sugars in meteorites found on Earth, but he said there was always a concern in those samples that the compounds might have been contaminated by the meteorites after they fell to Earth. "The discovery this time in the Bennu sample conclusively proves the authenticity of these results." He said.

The new study shows that asteroids could indeed deliver all the ingredients for life to Earth, or to other bodies in the solar system, such as Mars. In addition, since ribose but not deoxyribose was found in the sample, this finding also supports the "RNA World Hypothesis." This hypothesis holds that before cells appeared or DNA-based life forms evolved, the earliest life forms on Earth were composed of RNA molecules capable of storing genetic information and replicating themselves.