The two asteroids, Ryugu and Bennu, might have originated from the same asteroid collision or parent body that shattered on collision with other objects.
The team, led by the University of Arizona, has discovered that the asteroid’s shape and hydration levels provide clues to the origins and histories of this and other small bodies.
“Both asteroids have large impact craters on their equators, and their size suggests that these craters are some of Bennu’s oldest surface features. Since the craters cover the equatorial ridges, their spinning-top shapes must also have been formed much earlier,” as per the report by the University of Arizona.
Scientists are gaining a new understanding of asteroid Bennu’s memorable “spinning top” shape and where it comes from.
— NASA’s OSIRIS-REx (@OSIRISREx) June 1, 2020
“Using computer simulations that model the impact that broke up Bennu’s parent body, we show that these asteroids either formed directly as top-shapes or achieved the shape early after their formation in the main asteroid belt,” said Ronald Ballouz, co-lead author and OSIRIS-REx postdoctoral research associate at the University.
The scientists have also discovered that Bennu and Ryugu both asteroids contain water-bearing surface material in the form of clay minerals.
In a new paper published in Nature Communications, scientists from the OSIRIS-REx and Hayabusa2 teams argue that the YORP effect may not explain the shape of either Bennu or Ryugu. Both asteroids have large impact craters on their equators, and their size suggests that these craters are some of Bennu’s oldest surface features. Since the craters cover the equatorial ridges, their spinning-top shapes must also have been formed much earlier.
Bennu and Ryugu:
Asteroids Bennu and Ryugu are two near-Earth asteroids, known for their irregular spinning-top shape. The asteroid belt contains millions of oddly shaped rocky bodies, and some of them make their way closer to Earth.
Bennu, a near-Earth object with a diameter of approximately 500 meters (which is about 3/10 of a mile), orbits around the Sun every 436.6 days and comes within a close distance of 0.002 AU from Earth every six years.
Meanwhile, asteroid Ryugu, measuring around 900 was discovered in May 1999. The potentially hazardous asteroid is on an elliptical orbit around the Sun every 16 months, where it happens to cross the orbits of Earth and Mars.
Bennu is the target asteroid for the OSIRIS-REx mission, and Ryugu is the target of the Japan Aerospace Exploration Agency’s Hayabusa2 asteroid sample return mission. Ryugu’s samples have been collected by Japan’s Hayabusa2 spacecraft, and those samples are currently en route to Earth. NASA’s OSIRIS-REx mission has been orbiting Bennu since December 2018 and will collect samples from the surface later this year to also return to Earth.