Bennu asteroid contains building blocks of life, say scientists

The chemical building blocks of life have been found in granular dust from the asteroid Bennu, analysis has revealed.

Space rock samples brought back to Earth by NASA spacecraft contain a rich array of minerals and thousands of organic compounds.

These include amino acids, the molecules that make up proteins, as well as nucleic acid bases, the fundamental components of DNA.

This doesn't mean life ever existed on Bennu, but it does support the theory that asteroids carried these vital ingredients to Earth when they crashed into our planet billions of years ago.

Scientists believe that the same compounds could be transferred to other worlds in our solar system.

“What we've learned from this is amazing,” said Professor Sarah Russell, a space mineralogist at the Natural History Museum in London.

“It tells us about our origins and allows us to answer really, really important questions about where life began. And who doesn’t want to know how life began?”

The results were published in two papers in the journals Nature and Nature Astronomy.

Capturing a piece of Bennu was one of the most daring missions NASA has ever undertaken.

The spacecraft, called Osiris Rex, deployed a robotic arm to collect a 500-meter-wide piece of space rock before packing it into a capsule and returning it to Earth in 2023.

About 120 g of black dust was collected and distributed to scientists around the world. This may not seem like much material, but it turned out to be a real treasure trove.

“Each grain tells us something new about Bennu,” said Professor Russell, who studied the tiny specks.

About a teaspoon of the asteroid was sent to scientists in the UK.

A new study has found that space rock is full of compounds rich in nitrogen and carbon.

These include 14 of the 20 amino acids that life on Earth uses to build proteins, and all four circular molecules that make up DNA – adenine, guanine, cytosine and thymine.

The study also found numerous minerals and salts, suggesting that water was once present on the asteroid. The sample also contained ammonia, which is important for biochemical reactions.

Some of these compounds have been found in space rocks that have fallen to Earth, but others have not been discovered until now.

“It’s incredible how rich it is. It's full of minerals we haven't seen in meteorites before, and combinations of minerals we haven't seen before. It was very interesting to study,” said Professor Russell.

This latest study adds to growing evidence that asteroids brought water and organic material to Earth.

“The early solar system was really turbulent, with millions of asteroids like Bennu flying around,” explained Dr Ashley King from the Natural History Museum.

The idea is that they bombarded the young Earth, seeding our planet with the ingredients that gave us oceans and made life possible.

But Earth wasn't the only world hit by space rocks. Asteroids could also collide with other planets.

“Earth is unique in that it is the only place we have found life so far, but we know that asteroids carried these ingredients, carbon and water, throughout the solar system,” Dr King said.

“And one of the important things we're trying to understand now is, if you have the right conditions, why do we have life here on Earth, and could we potentially find it somewhere else in our solar system?”

This is a key question that scientists will continue to try to answer.

They have decades ahead of them studying the dust brought in from Bennu and the parts of our cosmic neighborhood that remain to be explored.