NASA’s OSIRIS-REx mission flies over asteroid Bennu for the last time


The OSIRIS-REx spacecraft is conducting a final flyby of the asteroid Bennu on Wednesday.

The spacecraft made history when it briefly landed on the asteroid on October 20, 2020, and collected a sizeable 2-ounce sample from the surface.

The sample, safely stored inside the spacecraft, will be returned to Earth in 2023.

The OSIRIS-REx mission, formally known as Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer, first arrived at the asteroid in December 2018 and has been orbiting ever since.

During Wednesday’s flyby, the spacecraft will get a final close-up of Bennu, capturing images of the asteroid’s surface from just 2.3 miles away. The images should reveal the aftermath of the sample collection event in October, which was a messy affair.

The asteroid’s surface was altered when the OSIRIS-REx sampling head sank 1.6 feet into the asteroid’s surface. He fired a charge containing nitrogen gas to disturb the surface material and make sample collection a bit easier. The spacecraft’s thrusters also launched material into the air as the spacecraft flew away from the asteroid after collecting the sample.

Gravity on the asteroid is weak, so rocks and dust were thrown and scattered throughout the process.

The asteroid Bennu has been with Earth for over a million years

Images captured by the spacecraft on Wednesday will show scientists how much the sample collection event altered the asteroid’s surface. The spacecraft will spend nearly six hours taking images of Bennu, allowing its cameras to see the asteroid complete one full rotation.

The route of this flyby is familiar to OSIRIS-REx, which conducted a similar one while searching for a landing site during surveys in 2019. Those 2019 images will be used with the new images to create before-and-after comparisons.

This artist's concept shows the planned flight path of NASA's OSIRIS-REx spacecraft during its final flyby of the asteroid Bennu.

During the flyby, the OSIRIS-REx instruments will collect data, allowing the mission team the opportunity to evaluate it after the tools were covered in dust during the collection event. The spacecraft can perform an extended mission after leaving the Bennu sample on Earth in September 2023, so this assessment can help teams make that determination.

Days after the flyby, all images and data will be sent to mission teams so they can analyze changes in Bennu and evaluate the spacecraft’s instruments.

OSIRIS-REx will remain in the area around Bennu until May 10, then begin a two-year, 200-million-mile journey back to Earth.

This illustration shows the OSIRIS-REx spacecraft departing from the asteroid Bennu to begin its two-year journey back to Earth.

“Leaving the vicinity of Bennu in May puts us in the ‘sweet spot’, when the exit maneuver will consume the least amount of fuel aboard the spacecraft,” said Michael Moreau, deputy director of the OSIRIS-REx project at the Center for NASA’s Goddard Space Flight in Greenbelt, Maryland, in a statement.

“However, with more than 593 miles per hour (265 meters per second) of speed change, this will be the largest propulsion maneuver performed by OSIRIS-REx since the approach to Bennu in October 2018.”

The asteroid sample could shed more light on the formation of the solar system and how elements such as water may have been sent to early Earth by asteroid impacts.

NASA spacecraft safely seals an asteroid sample to return to Earth

Once OSIRIS-REx approaches Earth in 2023, it will drop the capsule containing the sample, which will pass through Earth’s atmosphere and parachute into the Utah desert.

A team will be ready to retrieve the sample and transfer it to an aircraft hangar that will serve as a temporary clean room. The sample will then be taken to laboratories currently under construction at the Johnson Space Center in Houston.

“OSIRIS-REx has already provided incredible science,” Lori Glaze, NASA’s director of planetary science, said in a statement. “We are very excited that the mission is planning one more observation flyby of the asteroid Bennu to provide new information on how the asteroid responded (to the Touch-and-Go sample collection event) and to give a proper farewell.”

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