Asteroids like Bennu may have ‘delivered’ building blocks for life to Earth — Understanding NASA’s new discovery

In a major twist to the study of life beyond Earth, the National Aeronautics and Space Administration (NASA) said earlier this week that samples collected from asteroid Bennu contained a “mix of life’s ingredients.”

In research papers published Wednesday in the journals Nature and Nature Astronomy, scientists from NASA and other institutions shared results of the first in-depth analyses of the minerals and molecules in the Bennu samples, which OSIRIS-REx delivered to Earth in 2023.

The latest discovery, unveiled by the NASA on January 29, came as a bit of a surprise and posed many exciting questions such as “Why didn’t life form on Bennu?” Was it the temperature, the absence of an atmosphere, or the lack of other essential chemical components? The new papers don’t — and can’t — yet say.

According to Space.com, almost all of the NASA’s new findings about the Bennu samples suggested the asteroid had the right ingredients for life as we know it.

What NASA found in asteroid Bennu samples?

The samples from asteroid Bennu were delivered to Earth by NASA’s OSIRIS-REx mission in 2023. Since then, scientists and researchers are working around to clock to understand its components and examine life beyond Earth.

NASA said in a press release that studies of rock and dust from asteroid Bennu revealed molecules that are key to life on our planet. It also showed a history of saltwater that could have served as the “broth” for these compounds to interact and combine.

Here’s what NASA found in Bennu samples

1. A hot water extract from an asteroid Bennu sample was found to contain an “exceptionally high” and “surprising abundance” of ammonia, which is a key chemical building block for life. This may indicate that the material likely formed in a cold region of the solar system beyond Jupiter’s orbit.

Researchers found about 230 parts per million of ammonia. That’s about 100 times more than natural levels of ammonia in the soils on Earth, Times Magazine quoted Danny Glavin, senior scientist for sample return at NASA’s Goddard Space Flight Center Greenbelt, Maryland, as saying.

2. Fourteen of the 20 amino acids that life on Earth uses to build proteins were discovered within the Bennu samples.

3. The Bennu samples exhibit an equal abundance of left-handed and right-handed amino acids, like the mirror images of L and D-serine pictured below. This means that early Earth may have started out with equal abundances as well, before life developed a left-handed biology.

4. Scientists found all five nucleobases – the genetic components of DNA and RNA – within the Bennu samples. Adenine and thymine are two of the five nucleobases that encode genetic information in DNA and RNA.

5. Ranging from calcite to halite and sylvite, scientists identified traces of 11 minerals in the Bennu sample that form as water containing dissolved salts evaporates over long periods of time, leaving behind the salts as solid crystals.

In particular, they found a number of sodium salts, such as needles of hydrated sodium carbonate – salts that could easily have been compromised if the samples had been exposed to water in Earth’s atmosphere.

Some minerals found in Bennu, such as trona, were discovered for the first time in extraterrestrial samples.

What do these new findings mean?

NASA clarified that the findings “DO NOT show evidence for life itself, but they do suggest the conditions necessary for the emergence of life were widespread across the early solar system.” This increases the odds life could have formed on other planets and moons.

These building blocks for life detected in the Bennu samples have been found before in extraterrestrial rocks. “However, identifying them in a pristine sample collected in space supports the idea that objects that formed far from the Sun could have been an important source of the raw precursor ingredients for life throughout the solar system,” NASA said.

The US space agency said Bennu’s samples are pivotal in understanding what ingredients in our solar system existed before life started on Earth. The findings suggest that similar asteroids may have brought us the raw ingredients of life when they bombarded our planet billions of years ago, Times Magazine noted.

“This all supports the theory that asteroids like Bennu were among the sources that delivered water and chemical building blocks for life to Earth before life started here,” said Nicky Fox, associate administrator for NASA’s Science Mission Directorate, at a press conference just after both papers were released.

Jason Dworkin, OSIRIS-REx project scientist at NASA Goddard and co-lead author on the Nature Astronomy paper, said, “Data from OSIRIS-REx adds major brushstrokes to a picture of a solar system teeming with the potential for life. Why we, so far, only see life on Earth and not elsewhere, that’s the truly tantalizing question.”

Several questions remain

NASA pointed out that many amino acids can be created in two mirror-image versions, like a pair of left and right hands. It said that life on Earth almost exclusively produces the left-handed variety, but the Bennu samples contain an equal mixture of both.

“This means that on early Earth, amino acids may have started out in an equal mixture, as well. The reason life “turned left” instead of right remains a mystery,” researchers said.

This finding also calls into question scientists’ hypothesis that asteroids similar to this one might have seeded life on Earth, Nature journal reported.