Scientists Discover Key Building Blocks of Life in NASA Asteroid Samples

Analysis of asteroid Bennu samples suggests life’s essential chemical ingredients may have been widespread across the early solar system.

In an extraordinary breakthrough, scientists have uncovered a wealth of organic molecules, including some of the key building blocks of life, in samples taken from the asteroid Bennu. This surprising discovery supports the theory that the essential chemicals for life may have been common throughout the early solar system.

NASA’s OSIRIS-REx spacecraft, which launched in 2016, collected dust, soil, and rock samples from Bennu and returned them to Earth in 2023. The 4.5-billion-year-old asteroid, believed to have formed within the first 10 million years of the solar system's existence, provided a rare and pristine look into the early chemical makeup of space.

An analysis published Wednesday in Nature reveals that Bennu’s samples contained thousands of organic compounds, including 14 of the 20 amino acids that form proteins in life on Earth. Additionally, the samples included four nucleobases—the crucial components of DNA and RNA, which store and transmit genetic information within cells.

While the research did not find direct evidence of life on Bennu, the findings bolster the idea that asteroids, like Bennu, may have played a significant role in delivering the building blocks necessary for life on Earth. This discovery also raises the possibility that the conditions for life could be more prevalent on other planets and moons in the solar system than previously thought.

Nicky Fox, NASA's Associate Administrator for the Science Mission Directorate, emphasized the importance of the OSIRIS-REx mission in reshaping our understanding of the ingredients needed for life: “The OSIRIS-REx mission is already rewriting the textbook on what we understand about the ingredients thought to be necessary for the emergence of life in our solar system,” Fox said in a news briefing.

While similar organic molecules, such as amino acids, have been found in meteorites before, these space rocks have been altered by their fiery journeys through Earth’s atmosphere, potentially skewing results. The direct collection of samples from Bennu, untouched by Earth’s conditions, provides a much more reliable and clear picture.

“What’s so significant about the OSIRIS-REx Bennu findings is that those samples are pristine,” said Danny Glavin, an astrobiologist at NASA’s Goddard Space Flight Center. The return canister used to protect the Bennu samples from harsh conditions during re-entry ensures the samples remain free of contamination, offering higher confidence in their extraterrestrial origins.

The analysis revealed some unexpected findings, including a surprisingly high concentration of ammonia—approximately 100 times higher than the natural levels typically found in Earth’s soils. Ammonia is essential for various biological processes, including the formation of amino acids, which can then assemble into proteins.

Another discovery, detailed in a second study published Wednesday in Nature, involved traces of 11 minerals likely formed by the evaporation of water from Bennu’s parent asteroid. The salty crystals left behind resemble sodium-rich deposits found in dry lakebeds on Earth, like Searles Lake in California. “We now know from Bennu that the raw ingredients of life were combining in really interesting and complex ways,” said Tim McCoy, curator of meteorites at the Smithsonian National Museum of Natural History.

The minerals detected included sodium carbonate compounds like trona (commonly known as soda ash), a substance never before observed in extraterrestrial samples. Such briny mixtures have been theorized to exist on moons like Saturn’s Enceladus and the dwarf planet Ceres, where similar environments may exist for life to potentially develop.

These findings represent the first comprehensive analysis of the Bennu samples. Earlier in 2023, scientists announced preliminary results, which included the discovery of carbon and water in the asteroid’s clay minerals.

The Bennu samples are the first asteroid materials that NASA has collected and returned to Earth, though Japan’s Hayabusa missions previously delivered smaller samples from asteroids Itokawa (2010) and Ryugu (2020). While Bennu’s samples have already provided groundbreaking insights, more research is needed to understand why life emerged on Earth but not on Bennu, despite the presence of essential ingredients.

“What did Bennu not have that Earth did have?” asked Jason Dworkin, OSIRIS-REx project scientist at NASA’s Goddard Space Flight Center. “This is a future area of study for astrobiologists around the world to ponder, looking at Bennu as an example of a place that had all the stuff but didn’t make life. Why was Earth special?”