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NASA may well have succeeded in its first attempt to sample an asteroid on Tuesday when its OSIRIS-REx probe landed for a few moments on the surface of the asteroid Bennu, kicking up a dramatic shower of rocks and dust. During its six seconds in contact with the surface, the probe emitted a blast of nitrogen to stir up a sample of regolith, or asteroid dust, to capture on its specialized head and then took off again.
Mission investigators, masked and wearing matching blue NASA T-shirts, cheered as they listened to mission operations narrate OSIRIS-REx’s descent to Bennu: “O-REx has descended below the five meter mark; the hazard map is for TAG, “and then,” Declared Touchdown! ”- from the Lockheed Martin Space facility in Denver, Colorado.
“The OSIRIS-REx mission outperformed in every way,” NASA Administrator Jim Bridenstine told a news conference.
Just the task of landing successfully on Bennu was an achievement in precision and precision. After traveling some 207 million miles to the asteroid, the spacecraft attempted to safely descend to a location the size of two parking spaces and landed one meter from its target. And although the descent process took more than four hours, the landing itself had to be pre-programmed and performed autonomously, as it takes almost 19 minutes for a signal to travel from Earth to the current location of OSIRIS-REx.
Hearing OSIRIS-REx contact Bennu was a “momentous” experience, the mission’s principal investigator, Dante Lauretta, said moments later. “I can’t believe we made it!”
OSIRIS-REx (whose name is an acronym that refers to its research goals) was launched in September 2016, orbited the sun for a year, and then “came” to Bennu in 2018. Since then, his team has spent time on become familiar with this particular space rock, practicing flybys sometimes less than a mile away and mapping potential points on the surface for sample collection, including the Nightingale site where the probe made landfall on Tuesday.
That task was more difficult than expected. Based on long-range measurements of how quickly Bennu heats up and cools down in the sun’s rays, the OSIRIS-REx team hoped to find an asteroid whose surface looked more like a beach than a mountaintop. Instead, they struggled to find an area flat enough and free of obstacles to allow a safe landing. And they were concerned that the probe’s mechanism for collecting samples – the nitrogen puff designed to remove dust and rocks and propel them into some kind of high-tech air filter to be returned to Earth – wouldn’t work with a rocky surface. and stronger than anticipated.
Those fears were resolved Tuesday night, when OSIRIS-REx footage showed his touch and march on Bennu “stirred up a whirlpool of material that probably looks like nothing Bennu has seen in quite some time,” the administrator said. NASA Science Associate Thomas Zerbuchen. he said at the press conference.
Images from the landing suggest that the probe has likely successfully collected at least some material, Lauretta added at the same press conference, even crushing a fairly large rock with the probe’s sampling head. “We really made a mess on the surface of this asteroid,” he said, “but it’s a pretty mess, the kind of mess we expected.”
But information on how much material they collected will have to wait until the end of this week, when OSIRIS-REx will use onboard cameras to inspect its own sampling head, then extend its arm and turn. The maneuver allows the team to compare the probe’s “moment of inertia” (which refers to how mass distribution affects the way something rotates) before and after landing, and thus infer the weight of its payload. If determined not to If it manages to grab at least 60 grams of material, the team will have two more chances to land elsewhere in Bennu, starting in January.
Two Japanese missions have attempted to capture asteroid material in a manner similar to OSIRIS-REx, but both encountered unexpected obstacles and their sampling potential was far less than what NASA hopes this probe will bring home. Because its capacity to transport asteroid dust is much greater than that of its predecessors, the scientists involved in this mission hope that its very short time on Bennu’s surface will lead to a wealth of information.
Lauretta said NASA has already identified two different rock types on the surface of Bennu. The first, which he describes as a “dark, mound-like rock,” seems to be very weak compared to the rocks we are used to, and especially compared to the meteorites that generally survive their fall to Earth. The second is slightly brighter, “pierced by bright white veins or white inclusions,” he said, a mineral carbonate that is similar to the white crust that forms around the bathroom sink and is probably a bit stronger.
Once the sample arrives home, the geological exploration will begin in earnest. “It’s really amazing that these little specks of dust grains can tell you so much about how our universe formed, how our solar system formed, how asteroids like Bennu and Ryugu formed, and how Earth formed,” says Maitrayee Bose , a cosmochemist who studies the mineral composition of space dust. “So we can basically trace all the processes, from the really early part of the solar system to the current stage where we have the planets, quite easily by doing a very detailed characterization of these cosmic dust samples.” By examining their composition and the way they incorporate water into their structures, for example, Bose can learn what the temperature and pressure conditions were like when the dust formed, and thus infer what the environment in our nebula was like at that time.
Bose is particularly excited to measure the water content of Bennu’s regolith and, using that information, estimate how much water the asteroid and bodies of similar sizes could hold. That could provide key information about the origin of water on Earth and elsewhere in our solar system, and even give context for how it formed. “I’m trying to map out what are the predominant processes that could change or alter the composition of these materials,” he says. “Once I know that, then I can understand exoplanets, how they form. Can there be a similar situation like our solar system, where we could form a planet like Earth? “
The researchers will also use the information gleaned from their brief visit to measure the Yarkovsky effect on Bennu, or how the heat emanating from an asteroid can change its trajectory over time. That’s especially important because Bennu is considered one of the asteroids most likely to crash into Earth sometime in the next century. (Although that probability is still quite low). Understanding more about its potential trajectory could help with future missions that seek to stop that kind of impact.
But OSIRIS-REx faces a long journey before that investigation can begin. “The line is tied and the plumb bob dropped, and we’re excited, but now we have to bring it in and see if we catch the fish,” Zerbuchen said. “And then we have to take him home.”
After landing and sampling, the spacecraft executed a “flashback combustion,” in which it ignited its thrusters and began its eventual return to orbit around Bennu. It will now cool its heels, having warmed up significantly during its approach to the asteroid, while it waits for its team to evaluate its sample from the first attempt and decide whether it needs to return a second or third time.
The probe will stay with Bennu until the asteroid approaches Earth again, beginning its journey back to Earth in March 2021 and finally dropping its loot in the Utah desert in 2023. Then and only then can scientists begin the long process of unveiling the secrets it holds. .
