Dust and rock samples from the asteroid Bennu contain essential building blocks of life, scientists announced on Wednesday, revealing molecules never seen before in extraterrestrial samples.

The scientists who analysed the samples have found thousands of organic molecules, including 14 of the 20 protein amino acids present in living organisms on Earth, and all five nucleobases that make up genetic material, DNA and RNA.

“We now know from Bennu that the raw ingredients of life were combining in really interesting and complex ways on Bennu's parent body,” said Tim McCoy, a team member and curator of meteorites at the Smithsonian National Museum of Natural History in the US.

Their study indicates that Bennu’s parent asteroid developed or accumulated material from a reservoir in the outer solar system where ammonia ice is stable. Their findings bolster support for the hypothesis that asteroids like Bennu may have supplied key compounds such as ammonia, amino acids and nucleobases, helping build an inventory of prebiotic molecules that led to life on Earth.

A Nasa spacecraft named OSIRIS-ReX had collected the samples from Bennu in October 2020 and ferried them to Earth, delivering them via a sample return capsule that had touched down in Utah’s desert in September 2023.

The capsule brought 120 grams — roughly the weight of a soap bar — of the asteroid material which Nasa split into smaller samples that were loaned to researchers across the world for chemical analyses.

Their findings may help scientists understand better “how asteroids like Bennu evolved and how they may have helped make Earth habitable”, Sara Russell, a planetary mineralogist at the Natural History Museum in London and another team member, said in a media release.

Scientists have previously detected organic materials, amino acids, even nucleobases, in samples of meteorites, such as the Murchison meteorite that fell in Australia in 1969 or in samples from the Ryugu asteroid brought back by a Japanese spacecraft in December 2020. But the counts and complexity of such molecules in the Bennu samples far exceed those in earlier samples.

McCoy and his colleagues, in a paper published on Wednesday in the journal Nature, have reported detecting carbonates, sulfates, chlorides and fluorides that could have been left behind when salt-laced water evaporated from Bennu’s parent body.

In a second paper published in the journal Nature Astronomy, Daniel Glavin at the Nasa Goddard Space Flight Centre and his colleagues have reported finding 14 of the 20 amino acids found in living organisms on Earth, and all five nucleobases — adenine, guanine, cytosine, thymine and uracil — in the Bennu samples.

In previous research, scientists had detected uracil and nicotinic acid in samples from Ryugu. “But the other four nucleobases were absent in the Ryugu samples,” said Toshiki Koga, a team member at the Japan Agency for Marine Earth Science and Technology. “The difference in abundance and complexity of molecules between Bennu and Ryugu could reflect the differences in the environment to which these asteroids have been exposed in space.”