Life’s Essential Building Blocks Discovered in Asteroid Bennu Samples

According to research, rock and dust samples collected by NASA from the asteroid Bennu contain some of the essential chemical components of life.

These samples offer significant evidence that such celestial bodies may have provided early Earth with the fundamental materials necessary for the development of living organisms.

In 2020, NASA’s robotic OSIRIS-REx spacecraft gathered these samples from the near-Earth asteroid, a fragment of a once larger celestial object that formed approximately 4.5 billion years ago during the early solar system.

The samples were parachuted to Earth in 2023 inside a capsule released by OSIRIS-REx, which successfully landed in the Utah desert.

One study published in the journal Nature Astronomy found a wide array of organic compounds within the samples.

Another study in the journal Nature revealed that the samples included minerals formed from the evaporation of brine – salty water – on Bennu’s parent body, indicating a wet environment where prebiotic organic chemistry could have occurred.

The samples contained 14 of the 20 organic compounds known as amino acids, which are vital for creating proteins – complex molecules essential for the structure, function, and regulation of living organisms.

Specialists prepare samples from the capsule after it landed in Utah, September 2023 (Photo: NASA)

All five nucleobases, the genetic building blocks of DNA and RNA in all terrestrial life, were also detected in the samples.

During the early solar system, Earth and various moons experienced bombardment by asteroids and other space debris carrying water and organic compounds.

“The identification of these critical life-building blocks in the Bennu samples bolsters the hypothesis that asteroids and fragments contributed the raw materials that led to life on early Earth,” stated astrobiologist Danny Glavin from NASA’s Goddard Space Flight Center in Maryland, who led one of the studies.

“Moreover, the presence of these chemical building blocks in space and their widespread occurrence increases the likelihood that life may have originated beyond our planet,” Mr. Glavin added.

Organic compounds consist of one or more carbon atoms bonded to other elements, typically hydrogen, oxygen, nitrogen, and sulfur.

All life on Earth is carbon-based and comprises various organic compounds, including amino acids that form proteins and nucleobases.

A nucleobase is a nitrogen-containing compound that encodes genetic information.

DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are fundamental biomolecules in cell biology.

DNA encodes the genetic blueprint of an organism, while RNA transmits genetic information from DNA to facilitate its application.

“All biology is built on organic compounds.

The genesis of life involves organic chemistry, some aspects of which are preserved in these 4.5 billion-year-old rocks,” explained astrobiologist and co-author of the study, Jason Dworkin, the OSIRIS-REx project scientist.

The organic compounds from Bennu have previously been identified in meteorites that landed on Earth.

However, concerns about potential contamination from Earth-based sources persisted.

The samples were preserved in pristine condition.

“We can rely on these findings,” asserted Mr. Glavin.

Bennu’s icy parent body, estimated to be about 100 km in diameter, likely formed in the outer solar system and was destroyed approximately 1-2 billion years ago.

The remnants eventually morphed into Bennu and other “rubble pile” asteroids – loose aggregates of rocky material rather than cohesive entities.

In its early history, some ice within the parent body melted, creating brine.

The minerals formed from this brine’s evaporation had not been previously discovered in Earth-bound meteorites.

“The brines produced an environment where elements and simple organics could merge to form more intricate prebiotic compounds that are crucial in the journey towards life,” remarked geologist Tim McCoy, curator of meteorites at the Smithsonian Institution’s National Museum of Natural History in Washington and lead author of one of the studies.

The researchers did not uncover any direct evidence of DNA or RNA within the samples.

“The range of simple protein amino acids and nucleobases found in Bennu is significantly distant from anything that could be classified as ‘living,’ such as a more complex self-sustaining chemical system capable of replication and evolution, which comprises larger polymers – proteins and nucleic acids found within cells,” Mr. Glavin concluded.

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