Ancient asteroid reveals solar system’s secrets

Unique and ancient Bennu asteroid fragments brought to Earth by a Nasa spacecraft are helping Australian scientists unlock secrets about the solar system and how life formed. Photo / Nasa via X

Unique and ancient asteroid fragments brought to Earth by a Nasa spacecraft are helping Australian scientists unlock secrets about the solar system and how life formed.

The tiny samples were harvested by the Osiris-Rex spacecraft in 2023 beyond the Moon more than 300 million kilometres and several years travel from Earth on the asteroid Bennu.

“They are kind of relics of the early solar system,” planetary scientist Associate Professor Nick Timms told AAP on Saturday.

“They’ve been hanging around and not really changed too much since before the planets were formed.”

Surprise! (again)

Asteroid Bennu continues to reveal the unexpected. A new #OSIRISREx paper explains how its dust holds essential components for life and how the sample mirrors a type of rock found at mid-ocean ridges on Earth. Read more: https://t.co/I8Cez2HPs0 pic.twitter.com/4q8ep6DRLa

— NASA Astromaterials (@Astromaterials) July 2, 2024

Timms said the particles, which haven’t been contaminated by the Earth’s ecosphere like meteorites, were answering “age-old questions about how we came to be and our place in the cosmos”.

“Bennu is remarkable, it’s so close to being exactly the same composition as the sun,” he said.

Analyses showed Bennu, which is 4.5 billion years old and about 500m across, was among the most chemically primitive materials known to humans.

“We don’t quite have anything like it in all the thousands and thousands of meteorites that landed on Earth,” Timms said.

“The sample has pre-solar grains created before our solar system existed, which can provide a detailed biography of the lives of ancient stars.

“Most of the pieces are almost like soil, they could crumble in your hand, they’re very soft.”

Researchers from Curtin University’s School of Earth and Planetary Sciences found water and carbon locked in Bennu’s minerals.

“An early Earth might have been bombarded with this type of asteroid, it could have provided both the water and some of the carbon, which eventually started to evolve into carbon-based life forms,” Timms said.

“Those things have always been mysteries, and we don’t have all the answers right now but we’re certainly piecing together what could have gone on in the early solar system to make Earth unique.”

The samples also contained several unexpected components, such as magnesium-sodium phosphates that further suggest Bennu could have experienced chemical environments involving water.

“We also found other trace minerals, which offer clues as to the processes which have happened on Bennu over billions of years, such as temperature and pressure conditions,” Timms said.

“These trace minerals help paint a picture of Bennu’s evolution and offer insights into the early solar system and how the different planetary bodies were created.”

A global team of scientists, including the Curtin researchers, will continue studying samples from Bennu as Nasa releases more.

The Curtin team’s study was published in Meteoritics and Planetary Science.