This image shows sample site Nightingale, OSIRIS-REx’s primary sample collection site on asteroid Bennu. The image is overlaid with a graphic of the OSIRIS-REx spacecraft to illustrate the scale of the site. NASA/Goddard/University of Arizona
NASA’s OSIRIS-REx craft has been exploring asteroid Bennu since last year. But the craft isn’t only imaging the asteroid — it also plans to land on it and collect a sample. Now, after a year of observing the asteroid’s surface to find the perfect spot, a landing site has been chosen.
OSIRIS-REx, which stands for Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer, had previously imaged four possible landing sites nicknamed Sandpiper, Osprey, Kingfisher, and Nightingale. Landing on the asteroid is proving difficult because the team had expected to find a beach-like surface with flat areas for the craft to touch down. But in fact, the surface of the asteroid is covered with boulders which present a hazard to the landing craft.
Despite that, the team was able to choose four potential locations that would work for a landing. “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,” Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona in Tucson, said in a statement. “Of the four candidates, site Nightingale best meets these criteria and, ultimately, best ensures mission success.”
The Nightingale site is located in a crater 460 feet (140 meters) wide, on the northern part of the asteroid. Images of the area show that its regolith, or soil, is dark and relatively smooth, which makes for an easier landing. The crater is thought to be relatively young, which means the regolith there is fresher and ideal for taking a sample. Also, as the location is to the north, the region is lower in temperature than other parts of the asteroid which helps to preserve surface material.
However, Nightingale still provides some challenges. The team was expecting to have a space of up to 164 feet (50 meters) wide to land in. Now, they will need to be even more accurate in their landing to hit the much smaller target site of 52 feet (16 meters) diameter. They’ll also have to carefully avoid a large boulder on the eastern rim of the crater which could be a hazard to the craft.
“Bennu has challenged OSIRIS-REx with extraordinarily rugged terrain,” Rich Burns, OSIRIS-REx project manager at NASA’s Goddard Space Flight Center, said in the statement. “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.”
The sample collection mission is targeted for August next year, with OSIRIS-REx set to leave Bennu in 2021 and return to Earth in 2023.