Asteroid Bennu has all five amino acids for genetic material

Rock samples from the asteroid Bennu inspire scientists. Analyses show that the asteroid not only has minerals that are necessary for life as it exists on Earth. Bennu also contains all five amino acids that make up terrestrial genetic material. The NASA mission with the Osiris-Rex probe , which collected samples on Bennu and dropped them over the Earth in 2023, is paying off scientifically. Osiris-Rex stands for Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer.

The mission yielded a total of 121.6 grams of sample material, more than double the target quantity. A Bennu stone is on display at Smithsonian's National Museum of Natural History in the US capital Washington. Other Bennu samples are being studied by NASA and several other research institutions.

All genetic building blocks

Researchers have made exciting discoveries: A large American-Japanese-German group led by NASA's Goodard Space Flight Center reports "that Bennu samples are rich in volatiles and contain more carbon, nitrogen and ammonia than samples from the asteroid Ryugu and most meteorites. "We detected amino acids (including 14 of the 20 used in terrestrial biology), amines, formaldehyde, carboxylic acids, polycyclic aromatic hydrocarbons, and N-heterocycles (including all five nucleobases found in DNA and RNA), as well as about 10,000 nitrogen-containing chemical species," they write in their research report in the journal Nature Astronomy.

The abundance of amino acids and other soluble organics suggests that they were formed at low temperatures, possibly in ammonia-containing liquids: "The parent asteroid of Bennu evolved in, or retrieved ice from, a reservoir in the outer solar system where ammonia ice was stable."

The five ergbut amino acids are adenine, cytosine, guanine, thymine and uracil. They form DNA (without uracil) and RNA (without thymine). According to the Smithsonian, this is the first time that all of these chemical substances have been detected on an asteroid or meteorite.

Soda ash

Traces of hydrous soda (sodium carbonate compounds) were also detected for the first time on an asteroid or meteorite. This was achieved by electron microscopic analysis of a Bennu sample by another team of researchers, led by scientists from the Natural History Museums in Washington and London. On Earth, soda occurs naturally in evaporated salt lakes. The scientists have found a total of eleven minerals that probably originate from a brine-like environment on Bennu's parent asteroid.

However, as they explain in an article published in Nature, the chemical profile differs from terrestrial brines. Bennu is rich in phosphorus, which is comparatively rare on Earth, but Bennu lacks boron, which is common in hypersaline soda lakes on Earth. In these respects, Bennu is similar to meteorites studied, but not to the typical Earth profile. The evaporated minerals of Bennu therefore originate from the early phase of the formation of our planetary system.

"We now know that we have the basic building blocks for the path to life," said meteorite researcher Tim McCoy from Smithsonian's Natural History Museum in Washington. "But we don't know how far the environmental conditions (Bennus) allowed it to go down that path." "Together we have made enormous progress in understanding how asteroids like Bennu evolved and how they may have helped make Earth habitable," added his British colleague Sara Russel. She specializes in cosmic mineralogy.

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