Asteroid Bennu carries all ingredients to kick-start life as we know it

All the necessary ingredients to start life as we know it have now been found in samples from asteroid Bennnu. This shows that asteroids could have brought all the prerequisites for life to Earth – and perhaps to other places.

In 2020, NASA's OSIRIS-REx mission recovered samples from Bennuan asteroid that orbited the Sun at a distance of hundreds of millions of kilometers, between Mars and Jupiter. Mission returned samples to Earth in 2023. Since then, small quantities of the collected 121 grams have been sent to laboratories around the world for analysis so that experts detecting each type of biological compound can get to work.

The first studies revealed the presence water, carbon and a few organic molecules. This was followed by the discovery amino acids, formaldehyde, and all five nucleic acid bases found in RNA and DNA.as well as phosphates. However, this is not enough to piece together the molecules that carry genetic information. The rungs of the RNA and DNA ladder contain sugars—ribose in RNA and deoxyribose in DNA—and it was missing from early analyzes of Bennu's material.

Now, Yoshihiro Furukawa from Tohoku University in Japan and his 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 of the mixture.

This revealed the presence of ribose as well as other sugars including lyxose, xylose, arabinose, glucose and galactose, but not deoxyribose.

“This is a new discovery of sugars in extraterrestrial materials,” says Furukawa, adding that the metabolism of almost all life depends on glucose.

“This is such a brilliant result of the OSIRIS-REx mission,” says Sarah Russell at the Natural History Museum in London, who was not part of the team, but who also works with Bennu samples. “The only missing ingredient was sugar, which has now been reported, so all the ingredients of RNA are now known to be contained in primitive asteroids.”

Furukawa and his colleagues believe the sugars formed from formaldehyde-containing brines in the parent asteroid from which Bennu came, which is believed to have contained more liquid and had more reactions.

“Earlier this year we reported the detection of salts in a returned sample and suggested that Bennu's parent body may have had pools of salt water on it,” Russell says. “Such an environment would provide ideal sites for the preparation of the complex organics we see at Bennu.”

There is evidence of brines on Saturn's moon Enceladus And dwarf planet CeresThis suggests that the ingredients for life may be abundant in the solar system, Russell says.

Furukawa's work has previously discovered ribose and other sugars in meteorites found on Earth, but he says there was always a concern that these compounds could have entered the rock through contamination once they reached Earth. “This result in the Bennu sample ensures that these results were true,” he says.

The new work shows that asteroids could indeed deliver all the ingredients needed for life on Earth or on other solar system bodies such as Mars, Furukawa says. This also supports the RNA world hypothesis for origin of life because ribose was discovered, but deoxyribose was not.

This idea suggests that the earliest life on Earth, long before cells or DNA-based life, consisted of RNA molecules that contained genetic information and could reproduce.