It turned out to be different. How asteroid Bennu surprised a NASA spacecraft and nearly killed it (photo)

When the OSIRIS-REx spacecraft flew to the asteroid Bennu, it discovered an object that looked different and had different properties than scientists expected, writes Space.

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NASA scientists were inspired by the success of Japan’s Hayabusa mission when planning the OSIRIS-REx mission to study the asteroid Bennu and take samples from its surface. In 2010, for the first time in history, a spacecraft took rock samples from the Itokawa asteroid and returned them to Earth. Previously, scientists had found that the cosmic rock covered with rocks also had smooth plains consisting of small stones, thanks to the surface photographs taken by the device.

But despite some external similarities between the two asteroids, Bennu turned out to be completely different. Only when OSIRIS-REx flew by the asteroid Bennu in 2018 did scientists discover that there was not a single flat region on the surface, instead of large plains of small rocks interspersed with clusters of rocks. This means the device cannot descend to the surface to collect samples.

With the help of images sent back to Earth by the spacecraft, scientists managed to find a place where there were still not many large rocks. Thus, it was possible to land here to collect samples.

But to do this, scientists had to remotely reprogram OSIRIS-REx because it initially needed to land in an area at least 50 meters wide. Now the device had to land accurately in a 10-meter-wide crater.

The device landed normally, but when it began collecting local rock samples, something unexpected happened. Contrary to scientists’ expectations, the asteroid’s surface resembled a swamp in its properties. OSIRIS-REx dove into Bennu to a depth of 50 cm in a matter of seconds, and when it tried to get out after taking samples, a huge wall of debris rose from the crater due to its engines firing. This caused the device to sink even deeper.

Scientists later admitted that although OSIRIS-REx managed to escape the crater, an unfortunate combination of circumstances in the form of a pile of debris could have led to the device’s demise. Scientists incorrectly predicted Bennu’s surface and density. The surface layer turned out to be unexpectedly loose; this has not been demonstrated by observing the apparatus from orbit around the asteroid.

Astronomers still don’t know why Bennu’s surface has these features. It’s possible that smaller sand-like particles seeped into the asteroid’s interior through gaps between larger pieces of rock, leaving a lot of empty space in the surface layer. This could explain the unexpectedly low surface density, as well as the overall density of the asteroid, which appears to be much higher than the surface density.

OSIRIS-REx collected many more samples from asteroid Bennu than scientists had planned. And it will deliver these samples to Earth on September 24. The results of the research will be presented at the end of this year.

Focus I have already written that the world’s first mountain peak crater, formed as a result of an asteroid impact, was discovered in China. A nearly 1-mile-wide depression at the top of a mountain in China is actually where a space rock crashed.