NASA Selects a Sample Collection Site on Asteroid Bennu

After grappling with the rugged reality of asteroid Bennu's surface, the US space agency has finally selected a sample collection site on asteroid Bennu.

The OSIRIS-Rex mission team selected the site designated "Nightingale" - located in a crater high in Bennu's northern hemisphere.

Since its arrival in December 2018, the OSIRIS-REx spacecraft has mapped the entire asteroid in order to identify the safest and most accessible spots for the spacecraft to collect a sample.

The team spent the past several months evaluating close-range data from four candidate sites in order to identify the best option for the sample collection, NASA said in a statement on Thursday.

"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," said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona in Tucson.

The site Nightingale is located in a northern crater 460 feet wide.

Nightingale's regolith - or rocky surface material - is dark, and images show that the crater is relatively smooth.

Because it is located so far north, temperatures in the region are lower than elsewhere on the asteroid and the surface material is well-preserved.

The crater also is thought to be relatively young, and the regolith is freshly exposed.

This means the site would likely allow for a pristine sample of the asteroid, giving the team insight into Bennu's history.

The mission has also selected site Osprey as a backup sample collection site. The spacecraft has the capability to perform multiple sampling attempts, but any significant disturbance to Nightingale's surface would make it difficult to collect a sample from that area on a later attempt, making a backup site necessary.

In any situation where a follow-on attempt at Nightingale is not possible, the team will try to collect a sample from site Osprey instead.

"The team has adapted by employing a more accurate, though more complex, optical navigation technique to be able to get into these small areas. We'll also arm OSIRIS-REx with the capability to recognize if it is on course to touch a hazard within or adjacent to the site and wave-off before that happens," said Rich Burns, OSIRIS-REx project manager at NASA's Goddard Space Flight Center.

OSIRIS-REx sample collection is scheduled for the latter half of 2020, and the spacecraft will return the asteroid samples to Earth on September 24, 2023.