Did life originate in Bennu asteroid? What scientists say

Did an asteroid plant the seeds of life on Earth? Recent research has provided the strongest evidence yet on this theory.

A team of scientists reported in the journal Nature on Wednesday that the near-Earth asteroid, known as Bennu, contains a wealth of organic molecules, including many that are building blocks of life.

“What we’ve learned from it is amazing,”  Prof Sara Russell, a cosmic mineralogist from the Natural History Museum in London told BBC.

As researchers dig deeper into the samples of the space rock, they are uncovering captivating hints about how the chemistry of life may have started far beyond our planet.

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“It’s telling us about our own origins, and it enables us to answer these really, really big questions about where life began. And who doesn’t want to know about how life started?” Russell further said.

What does discovery reveal? Here’s what we know so far.

But first, why do even study asteroids?

Asteroids are often called time capsules of the early Solar System. These rocky remnants, formed over 4.5 billion years ago, have remained largely unchanged since their creation, preserving vital clues about the conditions that existed when planets—including Earth—were taking shape.

Scientists believe asteroids may have played a crucial role in Earth’s history, particularly in the emergence of life. Some theories suggest that in the planet’s infancy, when Earth was constantly bombarded by space debris, asteroids delivered water and organic molecules—key ingredients for life.

However, studying asteroid chemistry on Earth is difficult. While meteorites that fall to our planet come from asteroids, they are exposed to our atmosphere and risk biological contamination. This makes it challenging to determine their original composition. So, the best way to analyse asteroid material is by collecting pristine samples directly from space.

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So far, only two countries have successfully brought back asteroid samples: Japan with its Hayabusa (2010) and Hayabusa2 (2020) missions and the United States with Osiris Rex (2023), bringing samples from Bennu asteroid.

Nasa’s most audacious space mission

Grabbing a bit of Bennu has been one of the boldest missions the American space agency, Nasa has ever attempted.

The Osiris Rex spacecraft, designed for asteroid sample collection, extended its robotic arm to gather material from the 500m-wide space rock. After securing the sample, it carefully stored it in a capsule and sent it on a return journey to Earth, finally landing in Utah in September 2023.

Bennu, a 4.5-billion-year-old asteroid, is believed to have taken shape within the first 10 million years of the Solar System’s formation.

Although the collected sample weighs just 120 grams, its scientific value is immense. The black dust retrieved from Bennu has been distributed to researchers worldwide and it has proved to be a treasure trove.

“Every grain is telling us something new about Bennu,” Russell, who’s been studying the tiny specks, told BBC.

What did the scientist discover?

The samples from Bennu have revealed some unexpected and fascinating surprises.

One of the most striking discoveries was an exceptionally high concentration of ammonia—about 100 times more than the natural levels typically found in Earth’s soil, according to Danny Glavin, an astrobiologist at Nasa’s Goddard Space Flight Center.

Ammonia is a crucial 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 i.e the DNA.

Another surprise was the presence of 11 previously unseen minerals, likely remnants of a briny mixture left behind when water evaporated from Bennu and its parent asteroid.

Tim McCoy, co-author of the study and curator of meteorites at the Smithsonian Natural History Museum in Washington, DC, said these salty crystals formed by this evaporation bear a strong resemblance to sodium-rich crusts found in Earth’s dry lakebeds, such as California’s Mojave Desert and Africa’s Sahara.

“It’s just incredible how rich it is. It’s full of these minerals that we haven’t seen before in meteorites and the combination of them that we haven’t seen before. It’s been such an exciting thing to study,” said Prof Sara Russell.

While these discoveries are groundbreaking, they also raise deeper questions about life’s origins. Scientists are now investigating why Earth—despite having similar building blocks—developed life, while Bennu did not.

“What did Bennu not have that Earth did have?” Jason Dworkin, an Osiris Rex project scientist at Nasa, told NBC News. “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?”

With input from agencies