2019 – 2020: Choosing a Touchdown Site from a Sea of Hazards 

This week, we are recapping noteworthy OSIRIS-REx mission events each day so you can catch up on anything you may have missed so far in NASA’s first mission to collect a sample from an asteroid.   

(Post #3 in a series of four) 

Pictured here are the four candidate sample collection sites on asteroid Bennu selected by NASA’s OSIRIS-REx mission. Site Nightingale (top left) is located on Bennu’s northern hemisphere. Sites Kingfisher (top right) and Osprey (bottom left) are located on Bennu’s equatorial region. Site Sandpiper (bottom right) is located on Bennu’s southern hemisphere. Nightingale was chosen as the sample collection site. CREDITS: NASA/Goddard/University of Arizona

Given Bennu’s unexpectedly rough terrain, NASA’s OSIRIS-REx team took extra time to evaluate potential sample collection areas. They looked for flat surfaces between numerous rugged boulders. They also looked for regions with fine grains on the surface that the spacecraft could easily ingest. Through their own analyses and a public mapping campaign, the mission team first identified more than 50 sites, whittled those down to 16, and then to the final four candidates. The spacecraft then spent a month investigating each of the four sites and sending home images so scientists could further evaluate them.  

A spot dubbed “Nightingale” by the team, set in a small crater, rose to the top of the list in December 2019. The size of a few parking spaces, Nightingale was the most promising location to meet both safety and sample-availability considerations. But it wasn’t perfect. The area was only about one-tenth the size the mission team had planned for. This put pressure on OSIRIS-REx navigation engineers to program the spacecraft to dodge boulders, such as a building-size one, nicknamed “Mount Doom,” during its 2020 autonomous navigation to a small spot on the surface. 

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Learn more: 

NASA Mission Selects Final Four Site Candidates for Asteroid Sample Return 

X Marks the Spot: NASA Selects Site for Asteroid Sample Collection 

Coming up tomorrow: “Touchdown! And Goodbye.” 

  — Lonnie Shekhtman