NASA Selects 4 Potential Sites for Asteroid Bennu Sample Return

Since December 2018, the OSIRIS-REx spacecraft has mapped asteroid Bennu’s entire surface to identify the most accessible and safest spots for collecting a sample. Now, NASA’s OSIRIS-REx team has selected four potential sites for the federal agency’s first asteroid sample return mission and they are named after birds native to Egypt.

The four candidate sample sites, which are called Kingfisher, Nightingale, Osprey, and Sandpiper, will be studied in further detail in order to select the final two sites, a primary and a backup, in December, said a NASA press release.

Even though the amount of samplebale material hasn’t been determined in each site yet, all of them were evaluated to ensure that the  OSIRIS-REx spacecraft will stay safe when it lands and gathers a sample from asteroid Bennu’s surface.

As the northern-most site, Nightingale is situated at 56 degrees north latitude on asteroid Bennu. There are many possible sampling regions in this site, which is located in a small crater surrounded by a larger crater that is 459 feet in diameter. Nightingale has mostly fine-grain, dark material and it has the lowest reflection (albedo) and surface temperature out of the four sites.

Located in a tiny crater near asteroid Bennu’s equator at 11 degrees north latitude, Kingfisher has the strongest spectral signature for hydrated minerals among the four sites. The crater, which has a diameter of 26 feet, is surrounded by boulders, even though the site itself doesn’t contain any large rocks.

Osprey is set in a small crater that is also located in asteroid Bennu’s equatorial region. Many potential sampling regions are present in this site, which has the strongest spectral signature of carbon-rich material out of the four sites. Different rock types in the surrounding area also suggest that the regolith (layer of unconsolidated rocky material covering bedrock) within Osprey could be diverse.

Asteroid Bennu’s southern hemisphere is home to Sandpiper. Located at 47 degrees south latitude, this site is a relatively flat area on the wall of a large crater that is 207 feet in diameter. Sandpiper may also contain unmodified water-rich material, since hydrated minerals are also present at the site.

Starting this fall, the OSIRIS-REx spacecraft will start analyzing the potential sites during the mission’s reconnaissance phase. The first stage of this phase will involve the OSIRIS-REx spacecraft executing high passes over each of the sites from a distance of 0.8 miles to confirm they contain sample-friendly material. Close-up images will also take note of the features required for the OSIRIS-REx spacecraft’s autonomous navigation to asteroid Bennu’s surface. Once data is collected from these passes, the team will choose the final primary and backup sample collection sites at the end of the year.

The second and third stages of reconnaissance are expected to start in early 2020, when the OSIRIS-REx spacecraft will conduct passes over the final two sites at lower altitudes and obtain higher resolution observations of asteroid Bennu’s surface, which will help it identify key features that will be used to navigate to the space rock’s surface for sample collection. OSIRIS-REx sample collection is scheduled to take place in late 2020 and the OSIRIS-REx spacecraft will return the asteroid samples to our planet on Sept. 24, 2023.

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