Update: OSIRIS-REx made contact with the surface on schedule, executed the sample-collection procedure, and fired its back-away thrusters. The “spacecraft did everything it was supposed to do,” declared a NASA team member during the livecast. No live images were received during the broadcast, but NASA said images should be available tomorrow morning. Stay tuned, as this looks to be a big success! Original article below.
NASA’s OSIRIS-REx spacecraft is finally ready to collect surface materials from asteroid Bennu. You can watch the action live right here starting at 5:00 p.m. EDT.
NASA has done all sorts of amazing things in its 62-year history, but the space agency has never collected surface materials from an asteroid. That could change today, as OSIRIS-REx is scheduled to make its Touch-and-Go maneuver on asteroid Bennu at 6:12 p.m. EDT (3:12 p.m. PDT) today. NASA’s live stream of the event can be seen in the video below, with coverage beginning at 5:00 p.m. EDT (2:00 p.m. PDT).
This is the first U.S. mission to attempt a sample return from an asteroid. In 2006, NASA’s Stardust probe collected and returned samples from a comet’s dust cloud. Japan managed to retrieve asteroid samples back in 2010 with the first Hayabusa mission; the second Hayabusa probe is currently en route to Earth with samples taken of asteroid Ryugu.
OSIRIS-REx, which stands for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer—pauses to catch breath—arrived at Bennu on December 3, 2018, where it’s been circling patiently ever since. The probe was built by NASA and Lockheed Martin, with the mission being led by planetary scientist Dante Lauretta from the University of Arizona.
Bennu is located 200 million miles (320 million km) from Earth, and it roughly resembles a spinning top. The asteroid measures 565 meters at its widest point, and it’s strewn with ancient material dating back to the early solar system. Scientists on Earth would very much like to get their hands on this material, as it could tell us how asteroids delivered water to Earth or even the chemical building blocks required for life.
Bennu, much to the chagrin of the OSIRIS-REx team, is littered with hundreds of boulders, the largest of which measure 190 feet (58 meters) across. As a result, it hasn’t been easy for the team to find a suitable landing spot, but an exhaustive analysis of the asteroid done over the past several months has led the team to a friendly site they’re calling Nightingale.
“We selected Nightingale because, by far, it has the most fine-grained material of all the four sample site candidates,” said Lauretta during a press event held in late September. “We spent early 2020 doing low-altitude reconnaissance passes over this site, ultimately imaging at about an eighth of an inch per pixel. We basically have incredibly detailed images covering the entire crater, and we counted all of those rocks.”
The sample mission itself began 11:00 a.m. EDT, when OSIRIS-REx’s thrusters were set to give a tiny squirt, nudging the spacecraft toward the surface. Lockheed Martin will be conducting operations from its facility near Denver, Colorado.
A computer on the probe will cross-reference its newly constructed hazard map with what it sees on the surface. Should things look too scary for a landing, an abort sequence will automatically be triggered, sending the probe back to the safe confines of orbit (OSIRIS-REx will be on its own during this phase of the mission, as it would take nearly 18 minutes for its signals to reach us on Earth). Simulations run by the team show there’s a 6% chance of an abort happening, given what we know of the Nightingale site, according to a statement put out by the University of Arizona. This wouldn’t be a huge deal, as the team can make multiple landing attempts.
Should things go swimmingly during the descent, the spacecraft will deploy its Touch-and-Go Sample Acquisition Mechanism (TAGSAM), which is located at the tip of its 11-foot-long (3.3-meter) arm. At the surface, the sampler head will blast some nitrogen gas to kick up materials, which should be easy enough, given the exceptionally low gravity on Bennu. TAGSAM will then scoop up fine grained material and bits of debris no larger than three quarters of an inch (2 cm). The entire collection sequence should last around 10 seconds, after which time the spacecraft will ascend and resume its orbit around the asteroid.
The OSIRIS-REx team will then pore over the footage to determine if the collection effort was a success and if further attempts will be warranted (the probe has three bottles of nitrogen gas).
“We’ll be able to tell if we were tilted, if gas blew out to the side, if material was sufficiently stirred up,” Lauretta said. “We also will have a very good indication of the exact location in Nightingale where we made contact, and we can compare that to our samplability map, to assess if we touched down in an area where there is abundant samplable material or one of the rockier locations.”
A second site, called Osprey, would be the likely second target should the team not be happy with the results. Mission planners would be satisfied with around 2 ounces (60 grams) of surface material, but the probe can collect upwards of 4 pounds (1.8 kg). Once this phase of the mission is complete, OSIRIS-REx will bid adieu to Bennu and begin a journey that will see it return to Earth in 2023.
Fun fact about Bennu: It’s one of the most threatening near-Earth objects known, with an estimated 1 in 2,700 chance of smashing into Earth at some point between 2175 and 2196. If Bennu were to defy these slim odds and strike our planet, the asteroid would unleash 1,200 megatons of explosive force, making it 24 times more powerful than Tsar Bomba—the largest nuclear weapon ever detonated.