There’s no wonder why astronomers had been especially concerned if there’s any chance for the Bennu asteroid to pay us an ‘unwanted visit’ at some point. The space rock measures over 262 meters in its radius, which means that we certainly don’t want it landing in our own backyard.
Despite its imposing size, Bennu was still vulnerable in the face of a small object. An impact between the two cosmic objects is what led to a rock slide and a huge crater, according to space.com. Scientists had been using NASA’s OSIRIS-REx spacecraft to follow the aftermath of the impact.
It was surprising that the impact generated the landslide. Instead, an object smashing into another in space at high speed should make material go upward.
Mark Perry, leader of the new research and who works at the Johns Hopkins University Applied Physics Laboratory (APL), explained the reason behind the landslide, as space.com quotes:
Because Bennu is so small, its escape velocity is less than a few tenths of a mile per hour, so any particle ejected faster than that would leave the surface,
These slow speeds are possible only if Bennu’s surface is weaker than we thought, even weaker than very loose, dry sand. This extremely low surface strength also means the material on a slope is easily disturbed, and that’s what led to the landslide.
NASA revealed last year that the Bennu asteroid does have a chance to hit Earth one day, but a very small one. Furthermore, it can happen only after 161 years, but we’re guessing that nobody plans to live that long. In order to determine the new risk, NASA scientists gathered the relevant data from the OSIRIS-Rex spacecraft that has been used to study the space rock up-close for years.