Updated at 7:30 p.m. ET
A NASA spacecraft successfully touched down on a skyscraper-sized asteroid 200 million miles away, in order to collect a small amount of rock and dust that can then be returned to Earth.
The probe, called OSIRIS-REx, is about as big as a 15-passenger van, and it was aiming for a specific spot inside a boulder-strewn crater. The maneuver was tricky and fraught with peril, as the spacecraft had to reach a safe area that's only the size of a few parking spaces.
Because of the coronavirus pandemic, only a skeleton crew was at the spacecraft's operations center at the Lockheed Martin Space Systems Facility in Littleton, Colo., to monitor the probe's progress.
They were only observers during the event, because it took more than 18 minutes for messages from the spacecraft to reach them. They received no images — only a trickle of data came back from the probe as it descended and relied on its on-board systems to survey the terrain and assess the hazards.
The team jumped up and cheered when they learned that the probe had determined that it was safe to proceed to the surface. Moments later, "touchdown" was declared.
"I can't believe we actually pulled this off," said Dante Lauretta of the University of Arizona, the principal investigator for the mission, who said he was feeling "transcendental."
"It's almost hard to process everything that's happening right now," said Lauretta.
Quickly, word came from the spacecraft that it had safely backed away from the surface, and everyone cheered again. In the coming days, researchers will get images and other data from the spacecraft that will let them assess how much of the asteroid it nabbed.
This spinning top-shaped asteroid, named Bennu, is one of close to a million known asteroids in our solar system. Scientists want to study it in part to improve our planetary defenses against potentially dangerous space rocks. Bennu, for example, has a small chance of someday striking Earth.
"Our most recent calculations suggest that it has about a one in 2,700 chance," says Lauretta. "The good news is such an impact would not occur for at least 150 years, and part of the OSIRIS-REx mission is to better understand that impact probability."
Scientists also want to study asteroids like this one because they're thought to be nearly pristine time capsules—left-over bits from the early solar system that have gone undisturbed for billions of years.
"Asteroids are relics of the earliest material that formed the planets," says Lori Glaze, director of NASA's planetary science division. "They hold key information to unlocking our understanding of how the solar system formed and how it evolved."
This mission is NASA's first attempt to collect a sample from an asteroid and bring it back to Earth, but others have tried it before. Japan's space agency has a spacecraft that's currently on the way home with a small amount of material taken from the asteroid Ryugu; it should arrive in December.
"There are some key differences," says Lauretta. He explains that NASA's rock collection equipment can hold onto a larger sample. While Japan's probe might bring home just tens of milligrams of material, OSIRIS-REx is capable of collecting up to two kilograms, or almost four and a half pounds.
OSIRIS-REX launched in 2016 and has been orbiting the asteroid since 2018. As soon as it arrived there, scientists got a close-up look at this space object and realized that Bennu was nothing like they thought. They'd expected the surface to be relatively smooth and covered with fine-grained material like sand. Instead, they saw boulders everywhere.
"When I first saw the rugged surface of asteroid Bennu, I knew we were in for a real challenge," says Lauretta.
The team spent a year mapping the asteroid in exquisite detail, finally settling on two craters where it looked possible to touch down: a primary target named Nightingale and back-up site named Osprey.
The spacecraft did low flybys to get high resolution imagery, in order to build 3-D maps that can used by its onboard navigation system. In April and August, the probe did two rehearsals, dipping down as close as about 130 feet above the asteroid's surface.
The sample collector is at the end of an 11-foot-long arm and looks "a bit like an air filter you might see in an older car," says Sandra Freund, OSIRIS-REx mission operations manager at Lockheed Martin Space. It's currently unclear how much dust and rock the collector managed to ingest.
The team should have enough information by October 30, however, to determine whether it's an acceptable amount to bring home or whether to go for an additional sampling attempt in January.
Eventually, whatever gets collected will be stowed in a secure return capsule, and the spacecraft will depart for Earth in March of 2021. Once it reaches our planet in September of 2023, it will release the sample return capsule, which will parachute down to Utah.
For Lauretta, who has worked on this mission for 16 years, it feels almost as if the spacecraft is part of the team. "We talk to it on a daily basis. It's kind of our eyes and our sensors, out deep in the solar system," he says. "We're going out there to retrieve this scientific treasure and bring it back to the Earth."
STEVE INSKEEP, HOST:
Today, the space agency NASA will try to land a spacecraft on an asteroid, a hunk of rock in space that is roughly the size of a large building on Earth. The spacecraft only needs to stay there for five to 10 seconds, just long enough to collect some dust and rocks, which is pretty cool if it works, which it might not. Here's NPR's Nell Greenfieldboyce.
NELL GREENFIELDBOYCE, BYLINE: The asteroid is named Bennu. It's about 200 million miles away, and it's a potentially dangerous asteroid.
DANTE LAURETTA: Our most recent calculations suggest that it has about a 1 in 2,700 chance of impacting the Earth.
GREENFIELDBOYCE: Dante Lauretta of the University of Arizona is the principal investigator for a NASA mission called OSIRIS-REx. He says the good news is this asteroid wouldn't hit Earth for at least 150 years.
LAURETTA: And part of the OSIRIS-REx mission is to better understand that impact probability.
GREENFIELDBOYCE: What's more - asteroids are like pristine relics of the early solar system, undisturbed leftovers from when the planets first formed. So NASA isn't the only space agency interested in asteroids. Japan's has already collected a tiny amount of asteroid material that's on its way back to Earth. It will get here in December. Lori Glaze is head of NASA's planetary science division. She says the agencies have been collaborating.
LORI GLAZE: And, of course, we'll be exchanging portions of each other's samples so that we can maximize the science.
GREENFIELDBOYCE: Assuming NASA's effort goes off without a hitch. Its probe arrived at Bennu a couple years ago, giving researchers their first up-close view of this asteroid. Lauretta says they were expecting a smooth, sandy surface.
LAURETTA: Immediately, I was struck by how rough and rugged and rocky the surface was.
GREENFIELDBOYCE: It's been a real challenge to find a relatively rock-free spot where the probe can be ordered to briefly touch down. Later today, operators will send the go command. As the spacecraft leaves orbit and ventures down, the scientists will only be able to watch a trickle of data coming back.
LAURETTA: There's nothing we can do to change the course of events. In fact, by the time we get the data, everything that happened was 18 1/2 minutes in the past because that's how far away the spacecraft is from the Earth.
GREENFIELDBOYCE: The spacecraft, which is about the size of a big passenger van, will head to a crater that's about the size of a tennis court, but it's filled with boulders.
LAURETTA: So we're actually targeting a site about half that size, about 10 meters across. This is roughly the size of a few parking spaces in a parking lot.
GREENFIELDBOYCE: If the spacecraft's onboard systems decide that it's likely to hit a dangerous rock, it might call off the attempt. If everything goes just right, the research team will know right away if they've touched the surface. Knowing if they've got a sample will take longer. Beth Buck is the mission operations program manager at Lockheed Martin Space.
BETH BUCK: Our first imagery will start coming in on Wednesday, and that will give us a much better feel for whether we have a sample or not and how the spacecraft is actually performing.
GREENFIELDBOYCE: With luck, they'll have collected everything from tiny grains to stones nearly an inch across. Heather Enos of the University of Arizona is the deputy principal investigator for the mission.
HEATHER ENOS: The best outcome would be that we would collect a massive sample. I mean, we say we have a requirement of 60 grams or two ounces, so we have the capability of collecting up to two kilograms. And I would love for that capsule to be completely full.
GREENFIELDBOYCE: By October 30, the team will decide whether or not to try another sample collection attempt in January. And in March, the spacecraft will start its two-year journey back home.
Nell Greenfieldboyce, NPR News.
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