An Asteroid Sample Just Changed What We Know About Life in Our Solar System

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• Two exciting new studies detail the life-supporting contents of a 4.3-ounce sample of the asteroid Bennu.

• The OSIRIS-REx mission returned to the sample to Earth in September of 2023, and these studies show that it contains amino acids, nucleobases, and minerals known as evaporites—all elements of life’s building blocks.

• While not a detection of life itself, this study shows that the Solar System may have been far more conducive to life in its distant past then we previously believed.

Some 4.5 billion years ago, a monster asteroid around 60 miles wide formed in the outer reaches of the Solar System—beyond the orbit of Jupiter. Around one to two billion years ago, this mega-asteroid broke apart in the Asteroid Belt, producing a chunk of rock that us ape-like inhabitants on the Solar System’s third planet would one day call “Bennu.”

Eventually, those intelligent mammals would send a spacecraft called OSIRIS-REx to retrieve a sample of this rock in an attempt to better understand the early universe and the chances of life hiding elsewhere in the Solar System (and beyond). On September 24, 2023, a 4.3-ounce Bennu sample—perfectly preserved within OSIRIS-REx’s nitrogen-filled glovebox—crash-landed in the Utah desert.

Now, twin studies published in the journals Nature and Nature Astronomy are writing the next chapter of Bennu’s incredible 4.5 billion-year-old-story—and this one’s a real doozy. After close examination of the unspoiled sample, NASA and other scientists from around the world have confirm it a treasure trove of life’s building blocks. In a press statement, NASA is quick to clarify that they haven’t found life, but that this collection of amino acids, nucleobases, and minerals known as “evaporites” suggests that the conditions for life to take hold were widespread across the early Solar System.

“NASA’s OSIRIS-REx mission already is rewriting the textbook on what we understand about the beginnings of our solar system,” Nicky Fox, associate administrator of the Science Mission Directorate at NASA Headquarters, said in a press statement. “Asteroids provide a time capsule into our home planet’s history, and Bennu’s samples are pivotal in our understanding of what ingredients in our solar system existed before life started on Earth.”

This discovery wasn’t completely unexpected. Scientists discovered evidence of water on Bennu back in 2018, and soon after retrieval of the sample, NASA confirmed Bennu was rich in carbon. But now we know just how rich it really was. The Nature Astronomy paper reports that the sample contains 14 of the 20 amino acids (which make proteins) found on Earth, all five nucleobases life uses for storing and transmitting genetic instructions, and high levels of ammonia—which can aid in the formation of amino acids.

If that wasn’t enough, another team—led by meteorite experts and cosmic mineralogists at Smithsonian’s National Museum of Natural History and the Natural History Museum in London—found 11 minerals that only form when water containing dissolved salts evaporates (aka “evaporites”).

“We also learned that these minerals, formed when water evaporates, disappear when exposed to water once again—even with the tiny amount of water found in air,” the authors co-wrote in a post on The Conversation. “That explains why we can’t find these minerals in meteorites that have been on Earth for decades to centuries.”

As with any major discovery, Bennu also inspires more questions. For example, life on Earth only produces what are referred to as left-handed amino acids, but the asteroid contains an equal amount of left and right amino acids. It’s still a mystery why life adopted this left-handedness, and one scientists eventually hope to solve as they gather more information.

“OSIRIS-REx has been a highly successful mission,” NASA’s Jason Dworkin, co-lead author on the Nature Astronomy paper, said in a press statement. “Why we, so far, only see life on Earth and not elsewhere, that’s the truly tantalizing question.”

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