Science for All | The strange surface of asteroid Bennu

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NASA’s space mission to study asteroid Bennu could have ended in disaster if it did not leave immediately after collecting samples from its surface in October 2020.

The space organisation has revealed its findings after analysing the data that was gathered when the Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) spacecraft touched down on the surface of asteroid Bennu at a site named Nightingale, to collect dust and rock samples. According to NASA, particles that make up the surface of Bennu are loosely packed together and lightly bound, and stepping on its surface is like “stepping into a pit of plastic balls that are popular play areas for children”, with a high possibility that you’d sink in the pit. It goes to show that the surface of the asteroid offers very little resistance to any force. Of course, a child sinking into a plastic-ball pit for fun and a billion-dollar spacecraft sinking into an asteroid have very different implications.

The OSIRIS-REx space mission was launched in 2016 with the objectives to improve our understanding of asteroids and how they can impact the earth, and also to study the formation of planets and beginning of life.

Bennu has proved to be an unpredictable space body. A member of the team commented that it was expected that the asteroid would be like a solid rock but turns out, it has empty spaces in the surface. Scientists were also surprised when in 2018 it was discovered that the surface of Bennu is covered with boulders. They had been expecting a “smooth, sandy beach” based on previous observations made from telescopes. Additionally, laboratory experiments did not predict that the sample collection would leave a large crater on the surface of the asteroid.

The new discovery about Bennu’s surface can be helpful in analysing the kind of hazard that asteroids that are barely held together by gravity or electrostatic force can pose in case they enter the earth’s atmosphere and break apart.

The spacecraft is expected to return to the earth by 2023.