In a few months, NASA’s OSIRIS-REx will touch down on asteroid Bennu and collect a sample of the asteroid's soil. In preparation for this crucial part of the mission, and to avoid any surprises, NASA has photographed every bit of the spinning-top asteroid. They want to know exactly what OSIRIS-REx is facing on its way down to Bennu's surface.
The new map is an incredible mosaic of 2,155 images delivering a resolution of 5 centimeters (about 2 inches) per pixel. To emphasize the unprecedented detail: this is the highest resolution map of any celestial body humanity has ever produced. It was possible due to the combination of Bennu's relatively small size, roughly several city blocks in diameter, and the close orbit OSIRIS-REx was on when the photographs were taken between March 7 and April 19 last year.
Thanks to the detailed view provided by the map, the mission team was able to first pick four possible sampling sites, since reducing it to two. The primary site is known as Nightingale, and the backup is called Osprey. Bennu's name comes from the Egyptian bird deity thought to be the inspiration behind the Greek mythological phoenix. All four potential landing sites are named after Earthly birds, while the 12 officially named features on the surface of the asteroid are named after mythical birds or birdlike beings.
The Nightingale site is a crater within a crater, rich in fine-grained material of different colors, so NASA hopes to get several insights about the composition of Bennu from the single sampling touchdown. Once the sample is collected, OSIRIS-REx will hang around until 2021, when it will fire up its engine and set a course for home. It should arrive back to Earth in September 2023.
OSIRIS-REx is the NASA’s first asteroid sample-collecting mission, and the third in history after the Japanese Hayabusa-1 returned to Earth in 2010 and Hayabusa-2, which has been surveying asteroid Ryugu, will return at the end of this year.
Asteroid Bennu is a potentially hazardous near-Earth object with a cumulative 1-in-2,700 chance of hitting our planet between the years 2175 and 2199. It appears to be a pile of rubble, which is even more clear in the high-resolution view of this map. OSIRIS-REx will have a few test run close-up orbits of the asteroid, just a few hundred meters from the surface before flying down to land on its surface later this summer.
OSIRIS-REx is currently not among the missions affected by the COVID-19 precautions currently put in place by NASA.