Bumpy Bennu

Asteroid Bennu: Massive rocks unlock secrets of the universe

Thermal images explain why Bennu looks like this.

The asteroid Bennu is an anomaly.

Its diamond-like shape and scraggly texture give it a memorable appearance — and make it a curious object for scientists to study.


It’s also extremely old and hasn’t changed much since it formed nearly 4 billion years ago.

Understanding Bennu can give researchers important insight into how the Solar System formed.

And our knowledge of Bennu’s makeup is changing, thanks to NASA’s OSIRIS-REx mission and new analyses of the rock’s surface texture.

NASA via Giphy


A study published October 6 in the journal Nature aimed to answer the question: Why does Bennu have so many big rocks on its surface?


Previously, researchers thought the asteroid would be mostly be covered in regolith — fine material made from dust, minerals, and broken rocks.

Since Bennu is so old, it would make sense that the rocks on its surface would be ground down over time.

But large boulders still exist there today, in addition to some regolith.

Writing in Nature, the researchers explain how this is possible: the rocks on Bennu are incredibly porous.



Because rocks and regolith emit different amounts of heat, the team used artificial intelligence to analyze thermal images of Bennu.


In places with more porous rocks, they found less regolith present.

This makes sense because porous rocks absorb physical impacts and don’t become brittle due to temperature changes. They resist breaking down into regolith.

This new understanding of Bennu’s landscape could shape hypotheses on how asteroids form, giving us a glimpse into how other Solar System objects came to life.


“Asteroids are thought to be fossils of the Solar System, so understanding the evolution they have undergone in time is crucial to comprehend how the Solar System formed and evolved."

And when OSIRIS REx returns to Earth in 2023 with samples from Bennu, we’ll be able to decipher even more mysteries about the strange asteroid.

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