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UArizona scientists' plan to collect the first sample from an asteroid finds its target

Posted at 3:47 PM, Dec 12, 2019
and last updated 2019-12-12 19:38:24-05

(CNN) -- NASA's OSIRIS-REx is on a mission to bring back the first sample from an asteroid, and the team behind it has found the perfect place to collect that material.

NASA announced Thursday that they've identified the "Nightingale" location, within a crater on the near-Earth asteroid Bennu's northern hemisphere.

The goal is for OSIRIS-Rex to retrieve a sample in 2020 and return it to Earth by 2023. Once collected, the sample will consist of about 30 sugar packets worth of material.

Since arriving at the asteroid last December, NASA's OSIRIS-REx mission has been mapping its surface to determine the best spot to collect samples next year.

But Bennu, which is 70 million miles from Earth, has been full of surprises. The asteroid is much more rugged than expected, so four potential sites where the spacecraft can "tag" Bennu were chosen with care. The mission scientists have considered the safety and accessibility of each site.

Bennu is covered in boulders rather than the large areas of fine-grain material that scientists expected. In order for the spacecraft to bump the asteroid and send up material for the sampler to collect it, the material must be less than an inch in diameter.

"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. "Of the four candidates, site Nightingale best meets these criteria and, ultimately, best ensures mission success."

The four sites are named after birds found in Egypt: Nightingale, Kingfisher, Osprey and Sandpiper. The asteroid, its surface features and the spacecraft itself have been named after Egyptian deities and mythological birds, according to NASA. All four sites are diverse in their location and features.

Nightingale is the most northern spot, with multiple possibilities for sampling in a small crater that's contained within a larger crater filled with dark, fine-grain material. The smaller crater is 230 feet wide and smooth, with lower temperatures that have helped preserve the surface material. It's also fairly new, meaning the material exposed within it is a pristine look into the asteroid's history.

Originally, the mission team thought that the spacecraft would have a sample site with a diameter of 164 feet, but the safe zone of the Nightingale site is only 52 feet. That's one-tenth of the space they thought they had to work with to sample the asteroid's surface. A boulder the size of a building also hovers on the eastern rim of the crater, which could cause the spacecraft harm as it backs away once the sample has been collected.

Osprey was chosen as a backup collection site in case Nightingale doesn't work out. Once the spacecraft gets close to Nightingale, it could disturb the surface and send up material, which would compromise any samples collected from the site.

Osprey is on the equator in a small crater, showing signs of carbon-rich material and diverse rocks, and it has several areas that could be sampled.

"Bennu has challenged OSIRIS-REx with extraordinarily rugged terrain," said Rich Burns, OSIRIS-REx project manager at NASA's Goddard Space Flight Center. "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."

In January, the spacecraft will begin reconnaissance flights over both sites, which will extend into the spring. Then, it will practice "touch and go" sample collection attempts until it's ready to collect in August. OSIRIS-REx will leave Bennu in 2021 and return to Earth in September 2023.

The mission

Bennu is the smallest body to ever be orbited by a spacecraft, just a little bit wider than the height of the Empire State Building, according to NASA. Bennu has a shape comparable to that of a spinning top, and it's a "rubble pile" asteroid, which is a grouping of rocks held together by gravity rather than a single object.

The mission -- which stands for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer -- launched in September 2016. It began orbiting Bennu in December 2018.

The sample from Bennu, a near-Earth asteroid, could help scientists understand not only more about asteroids that could impact Earth but about how planets formed and life began. The asteroid could pass close to Earth, closer than the moon, in 2135, with even closer approaches possible in 2175 and 2195. A direct hit is unlikely, but the data gathered during this mission can help determine the best ways to deflect near-Earth asteroids.

OSIRIS-REx's instruments have confirmed that hydrated minerals, including magnetite, are abundant and widespread on the asteroid. The asteroid is full of valuable materials that may even contain clues about how life began. Bennu is essentially a leftover from the formation of our solar system billions of years ago, although some of the minerals inside it could be even older.

Bennu is also older than expected, between 100 million and 1 billion years old, and probably originated in the main asteroid belt. Bennu probably broke off of a larger asteroid in the belt between Mars and Jupiter a couple of billion years ago. This knocked it through space until an orbit close to Earth locked it in place.