In 2016, the US National Aeronautics and Space Administration (NASA) launched a mission to deliver soil samples from the asteroid Bennu to Earth using the OSIRIS-REx (Origins Spectral Interpretation Resource Identification Security Regolith Explorer) automatic probe. It turned out that during the collection of materials in October 2020, the device risked forever getting stuck on an asteroid – there were many voids under the surface of Bennu.
Image Source: NASA / Goddard / University of Arizona
It came as a surprise to the team of engineers involved in the OSIRIS-Rex mission that the structure of the asteroid layer just below the surface is loose, consisting of loosely bound rock fragments with many voids. The spacecraft managed to avoid sinking under the surface of Bennu only due to the fact that at the right time its engines were turned on.
“We expected the surface to be quite hard. We saw a giant wall of debris flying off the sampling site. For spacecraft operators, it was really scary. It turned out that the particles that make up the outer shell of Bennu are so loosely bound to each other that they behave more like a liquid than a solid body.— said Dante Lauretta, professor of paleontology at the University of Arizona.
Bennu’s loose surface, made up of colliding rock fragments, will help scientists improve their understanding of how asteroids form. It is also expected that soil samples from the asteroid will help in the development of methods to protect the Earth from collision with similar space objects.
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