UA-led space mission blasted boulders around Bennu during historic touchdown last year

OSIRIS-REx didn’t just make history last year when it touched down on an asteroid 207 million miles from Earth. It also made a bit of a mess.

The University of Arizona-led space mission sent boulders flying and created a small new crater during its brief contact with the asteroid Bennu on Oct. 20. The damage can be seen in new images collected by the unmanned probe during its final flyby of the asteroid on April 7.

One 4-foot boulder was hurled about 40 feet when the spacecraft fired its thrusters to escape from Bennu after scooping up samples from the surface, said Dante Lauretta, the UA planetary sciences professor who heads up the mission.

“The rock probably weighs around a ton, with a mass somewhere between a cow and a car,” said Jason Dworkin, the mission’s project scientist at Goddard Space Flight Center, in a written statement.

Scientists compared high-resolution photos taken before and after last year’s touch-and-go maneuver.

The latest images, collected by the spacecraft from a distance of about 2.3 miles and released on Thursday, show a new depression at the sample site, where several large boulders are now visible that could not be seen before.

Where the escape thrusters hit the surface, small boulders were pushed into the shape of a campfire ring, similar to other craters on Bennu.

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“These observations were not in the original mission plan, so we were excited to go back and document what we did,” said Dathon Golish, a member of the OSIRIS-REx image processing working group, headquartered at UA. “The team really pulled together for this one last hurrah.”

This is NASA’s first mission to collect samples from an asteroid and return them to Earth. The gravel and dust scooped up last year is thought to be 4.5 billion years old and may hold clues about the formation of the solar system and the origins of life.

The spacecraft was launched in 2016 and entered orbit around Bennu at the end of 2018, after a 1.25 billion-mile journey to chase down the asteroid. Since then, OSIRIS-REx has traveled another 1 billion miles.

The mission will enter a new phase on May 10, when OSIRIS-REx will fire its main engine and begin its two-year journey back to Earth.

Once it gets here, the spacecraft will jettison a return capsule filled with asteroid samples that is slated to land under parachutes at a military test range west of Salt Lake City on Sept. 24, 2023.

That will mark the end of the mission, but not of OSIRIS-REx. Depending on available funding and the condition of the spacecraft, it may be sent out again to photograph another asteroid in near-Earth orbit.