Three years later, as the ship orbits a 4-billion-year-old asteroid called Bennu, they've finally determined where OSIRIS-REx will scoop up that sample. They announced the asteroid landing site, nicknamed Nightingale, on December 12.
“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, the mission's principal investigator and a professor of planetary science at the University of Arizona in Tucson.
Scientists had a tougher time than expected finding a smooth, shallow spot that would allow for a good sample while also keeping the spacecraft safe, according to Heather Enos, the missions's deputy principal investigator. After narrowing the list down to four sites — all named after birds — the group looked beyond quantifiable numbers and considered qualitative factors in picking Nightingale, Enos said.
Nightingale sits inside a 460-foot crater in the asteroid's northern hemisphere. Its well-preserved surface material and relatively young age are helpful factors in getting a good sample, according to NASA.
The scientists also chose a backup region, called Osprey, in case anything goes wrong at Nightingale. A building-sized boulder on the rim of Nightingale's crater, for example, could pose a hazard to OSIRIS-REx as it leaves the site.
The mission's next step is to conduct flyover trips over both Nightingale and Osprey, then start rehearsing the sample-collection procedure, which is scheduled for August. Next, it will leave the asteroid in 2021 to begin its two-year return trip back to Earth.
The goal is to return a 60-gram sample (the size of around 30 sugar packets) back to Earth for analysis. The team behind the mission hopes the material, which originated billions of years ago, can help uncover new answers about the origins of the solar system.
"We'll be able to kind of look back in time and see the way that these molecules developed," Enos said.
Enos, who became involved in the planetary science program at University of Arizona more than two decades ago, said the decision is a "huge milestone" in the mission, and also in her own life.
"To be involved in NASA's first sample return mission since the Apollo days, it has been the highlight of my career," she said.
She said the team popped Champagne to celebrate its decision, and hopes to continue to celebrate victories as the mission continues.