The Summary
- A NASA spacecraft brought samples from the asteroid Bennu back to Earth in 2023.
- The first in-depth analyses of that material have revealed organic molecules, including building blocks of life.
- The results bolster the theory that asteroids that crashed into Earth may have delivered the ingredients for life.
In samples taken from a distant asteroid, scientists have discovered a host of organic molecules, including key building blocks of life.
The surprising finding suggests the chemical ingredients necessary for life may have been widespread across the early solar system.
NASA’s OSIRIS-REx spacecraft, which launched in 2016, scooped up bits of dust, soil and rocks from the asteroid Bennu and then brought them to Earth in 2023. The 4.5-billion-year-old asteroid is thought to have formed in the first 10 million years of the solar system’s existence.
An analysis of that collected asteroid material, published Wednesday in the journal Nature, indicates that the samples included thousands of organic compounds and 14 of the 20 amino acids that life on Earth uses to form proteins. The samples also contained four “nucleobases” — the main components of DNA and RNA, which store and transmit genetic blueprints within our cells.
The researchers did not find evidence of life itself on Bennu; rather, their results bolster the theory that asteroids that crashed into Earth when it was young may have delivered the necessary ingredients for life to take hold. The findings could also mean that the chances life formed on other planets and moons in the solar system could be higher than scientists previously thought.
“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,” Nicky Fox, the associate administrator of NASA’s Science Mission Directorate, said Wednesday in a news briefing.
Similar organic molecules, including amino acids, have been detected in meteorites before, but these fragments of space rocks are imperfect specimens because they are studied after enduring fiery trips through Earth’s atmosphere.
Whereas meteorites have been exposed to and contaminated by conditions on Earth that could skew scientific results, gathering samples directly from an asteroid in space is like peering into a time capsule from the nascent solar system.
“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 that carried the Bennu samples shielded them from harsh conditions during atmospheric re-entry, Glavin said.
“The bottom line is: We have a higher confidence that the organic material we’re seeing in these samples are extraterrestrial and not contamination,” he said. “We can trust these results.”
In the samples from Bennu, the researchers stumbled on some surprises. For one, they found exceptionally high concentrations of ammonia — “about 100 times more than the natural levels of ammonia that you find in soils on the Earth,” Glavin said.
Ammonia is an essential ingredient in many biological processes, including as a building block to form amino acids, which in turn can link together into long chains to make proteins.
Another surprise was described in a second paper published Wednesday in the journal Nature: Researchers found traces of 11 minerals that were likely part of a briny mixture left behind after deposits of water evaporated off Bennu and its parent asteroid.
The salty crystals left behind by the evaporated water resembled sodium-rich crusts found in dry lakebeds on Earth, such as Searles Lake in California, said Tim McCoy, curator of meteorites at the Smithsonian Natural History Museum in Washington, D.C., and a co-author of both studies.
“We now know from Bennu that the raw ingredients of life were combining in really interesting and complex ways on Bennu’s parent body,” McCoy said in a statement. “We have discovered that next step on a pathway to life.”
The minerals detected included sodium carbonate compounds such as trona (sometimes referred to as “soda ash”) that the scientists said had never been observed in other extraterrestrial samples. Similar briny mixtures are thought to exist on Saturn’s moon Enceladus and the dwarf planet Ceres.
The two new studies represent the first in-depth analyses of the Bennu samples. In 2023, scientists announced preliminary findings, including traces of carbon and water locked up in clay minerals.
The soil and rock from Bennu are the first samples NASA has collected and brought back from an asteroid, but they were not the first in history. Japan’s Hayabusa mission in 2010 delivered to Earth a few micrograms of material from an asteroid called Itokawa. A second mission, dubbed Hayabusa2, delivered a small sample from an asteroid known as Ryugu in 2020.
While the samples from Bennu have already yielded intriguing results, more research is needed to understand what precisely causes life to emerge on one planet or moon and not others.
“What did Bennu not have that Earth did have?” said Jason Dworkin, an 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?”
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