After a year of ‘scoping out’ the boulder-scattered surface of asteroid Bennu (discovered on 11 September 1999 during a survey by Lincoln Near-Earth Asteroid Research), the Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-Rex) mission team has concluded that a site designated Nightingale (located in a crater high in Bennu’s northern hemisphere) is the best spot for the spacecraft to collect its sample.

The team has spent several months evaluating close-range data from four possible sites, chosen for investigation because they pose the fewest hazards to the spacecraft’s safety.

Dante Lauretta, OSIRIS-REx (www.nasa.gov) principal investigator at the University of Arizona in Tucson, said: “After thoroughly evaluating all four candidate sites, we made our final decision based on which site has the greatest amount of fine-grained material and how easily the spacecraft can access that material while keeping the spacecraft safe.

“Of the four candidates, site Nightingale best meets these criteria.”

Site Nightingale is located in a northern crater 140m wide.

Its regolith (rocky surface material) is dark, and images show that the crater is relatively smooth.

The crater is also thought to be relatively young, and the regolith is freshly exposed, allowing for a ‘pristine’ sample of the asteroid.

A back-up sample collection site — Osprey— has also been identified.

With the selection of final primary and back-up sites, the mission team will undertake further reconnaissance flights over Nightingale and Osprey, beginning this month and continuing through the spring.

Once these flyovers are complete, the spacecraft will begin ‘rehearsals’ for its first ‘touch and go’ sample collection attempt, which is scheduled for August.

The spacecraft will leave Bennu in 2021 and is scheduled to return to Earth in September 2023.