NASA's OSIRIS-REx mission returned samples from asteroid Bennu, revealing the presence of organic compounds essential for life. After the Bennu samples arrived, researchers began studying them, diving into a tale of rock, ice, and water that hints at how life could have formed on Earth.
Since the Bennu samples returned to Earth, researchers from numerous international institutions conducted thorough analyses. This marked the first comprehensive studies of extraterrestrial material, and surprising scientific results were rolling in.
Among the materials found in the Bennu sample was sodium carbonate, which on Earth appears at the bottom of lakes that dried up and were rich in sodium. These findings suggest that water was once present on Bennu, providing a potential environment for prebiotic chemistry. Scientists discovered thousands of organic molecular compounds in the Bennu samples, including abundant mineral salts, amino acids, nitrogen in the form of ammonia, and all five bases present in the molecules of DNA and RNA: adenine, guanine, cytosine, thymine, and uracil.
"We have discovered the next step on the path to life," said Tim McCoy, co-lead author of the Nature study and curator at the Smithsonian National Museum of Natural History. "There were things in the samples that completely blew us away. The richness of the molecules and minerals preserved are unlike any extraterrestrial samples studied before," said Professor Sara Russell, cosmic mineralogist at the Natural History Museum, London, and co-lead author of the paper published in Nature.
Researchers reported that evaporated water on Bennu once left behind a briny broth, where salts and minerals provided an environment for life's basic elements to interact and form more complex structures.
"Combining the ingredients of life with an environment of sodium-rich salt water, or brines, that's really the pathway to life," McCoy said. "It's telling us about our own origins, and it enables us to answer these really big questions about where life began. And who doesn't want to know about how life started?" Russell added.
The samples from Bennu are especially rich in phosphorus, including sodium-bearing phosphates and sodium-rich carbonates, yet the building blocks of cell membranes, made of phospholipids, were not found. Scientists emphasize that although the Bennu samples do not show evidence for life itself, the conditions necessary for the emergence of life were likely widespread across the early solar system.
NASA's asteroid samples from Bennu hold not only building blocks for life, including amino acids and all five DNA and RNA nucleobases, but also the salty remains of an ancient water world, containing briny residue with crucial compounds like sodium carbonate. Brines similar to those of Bennu have been detected on Saturn's moon Enceladus.
Researchers propose that the body from which Bennu originated may have been located in the outer solar system, where different conditions prevailed, as suggested by the isotopes and organic substances found in the samples.
This article was written in collaboration with generative AI company Alchemiq