NASA Selects Final Four Possible Sites For OSIRIS-REx Sample Collection

This photo shows asteroid Bennu’s boulder-covered surface. NASA/Goddard/University of Arizona

NASA’s OSIRIS-REx mission is an exciting and important one, the first mission to bring a sample from an asteroid back to Earth. The record-breaking spacecraft has been studying asteroid Bennu with the view to flying down and collecting a sample of regolith, the top loose soil on the surface, and then returning to Earth. Since its arrival last December, the spacecraft has been mapping the asteroid to find the safest and best place to collect the sample from.

NASA has now announced its final four potential locations, which are all named after birds. Kingfisher and Osprey are located around the ridge-y equator of Bennu, while Nightingale and Sandpiper are situated in the Northern and Southern hemisphere of the asteroid, respectively. These four birds are native of Egypt, complementing the other naming conventions for the mission, which are all named after the Egyptian deities, and the asteroid's surface features, which are named after mythological birds.

In December, NASA will announce its primary target and a backup location. These will undergo further scrutiny to make sure that the area has enough sampleable material. The collected material can be at most 2.5 centimeters (less than 1 inch) in diameter. However, finding this turned out to be more difficult than expected.

These are the four candidate sample collection sites on asteroid Bennu selected by NASA’s OSIRIS-REx mission.  NASA/University of Arizona

Bennu is a big pile of chunky rubble loosely held together by gravity. Initially, the spacecraft was looking for areas of fine material, about 50 meters (164 feet) across, to briefly touch down and scoop. However, no such areas exist on Bennu, so the team had to readjust the goal and selected areas between 5 and 10 meters (16 to 33 feet) in radius. To achieve that the team had to tighten its navigation requirements. Prudently, they had included 300 days in the mission schedule dedicated to problem-solving unexpected scenarios.

“We knew that Bennu would surprise us, so we came prepared for whatever we might find,” Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, said in a statement. “As with any mission of exploration, dealing with the unknown requires flexibility, resources and ingenuity. The OSIRIS-REx team has demonstrated these essential traits for overcoming the unexpected throughout the Bennu encounter.”

All four locations are in or near small craters and have multiple sampling regions within them. Current spectral analysis has revealed interesting characteristics in all their terrains, from potentially hydrated minerals to carbon-rich materials, and even a peculiar dark fine-grain soil with an extremely low temperature.

Over the next four months, the mission will continue to investigate the four locations and provide enough data to allow the team to make an informed decision. In early 2020, the spacecraft will investigate the final two sites at lower and lower altitudes and will come down to collect the sample in late 2020. Its return to Earth is scheduled for September 24, 2023.

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