NASA’s OSIRIS-REx could turn out to be the boldest space mission this century
This story has been updated to include the news of the successful completion of NASA’s OSIRIS-REx mission.
NASA safely delivered the oldest dirt ever collected back to Earth on Sunday morning, September 24, a tiny capsule parachuting gently to the Utah desert carrying a sealed container with a half-pound of rock and dust collected from the asteroid Bennu by the robotic spacecraft OSIRIS-REx.
It is by far the largest sample of alien-world material delivered back to Earth since NASA’s final Moon landing, Apollo 17, in 1972, and the sample is expected to contain water, amino acids, and maybe even more complicated molecules—the building blocks of proteins. The dirt scooped from the tiny asteroid, which will be flown to NASA’s Johnson Space Center on Monday, is presumed to be unchanged since the solar system and Earth formed 4.6 billion years ago.
The flight of OSIRIS-REx out to the asteroid Bennu and back has gone virtually flawlessly, from its launch in September 2016, to the navigation that allowed the spacecraft to chase down an asteroid just three-tenths of a mile long, to the mission’s return on exactly the day predicted at launch, after traveling 3.8 billion miles, equivalent to flying out to Uranus and back.
The $1.2 billion mission has gone so well that even as the sample capsule streaked back through Earth’s atmosphere at 27,000 mph, the actual asteroid-chasing spacecraft—OSIRIS-REx itself —was re-oriented and then fired its engines to go chase down a second asteroid, on a bonus mission.
OSIRIS-REx also delivered an unanticipated bonus: what looks to be four times the amount of asteroid rocks and dirt scientists hoped to retrieve, all the more material available for study.
OSIRIS-REx could turn out to be NASA’s boldest and most consequential space mission so far this century.
The only hiccup in the mission? The moment when the boxy spacecraft arrived at Bennu. “When we got to Bennu,” says Dani DellaGuistina, a planetary scientist at the University of Arizona and second-in-command of the OSIRIS-REx mission, “we were like, ‘Oh crap. That’s not what we expected. At all.’”
The Bennu asteroid turned out to be weird
“The asteroid defied our not-imaginative-enough expectations,” says DellaGuistina. “But that’s why we do this, right? If we had it completely figured out, what’s the point of going?”
Bennu was weird in ways that were humbling for DellaGuistina and the dozens of scientists and engineers working on OSIRIS-REx, and mystifying in ways that are scientifically challenging and revealing.
Bennu is a small asteroid—1,673 feet across, with 20 acres of surface, and a circumference at the equator of about a mile. It’s about the size of a big domed stadium, zooming through space at 60,000 mph.
Years of study and planning had led the O-REx team to conclude that Bennu was covered in sandy, small-grain material with plenty of wide-open spaces for a hovering spacecraft to approach.
But when O-REx arrived, Bennu turned out to be rugged and rocky, craggy with ridges and outcrops, and almost no open spaces for the wide-winged OSIRIS-REx craft to approach without risking a collision. The flight plan for getting O-REx to Bennu’s surface had to be rethought and redesigned.
Then the surprises continued.
After spending months orbiting Bennu at an altitude of just 1 kilometer—about 3,300 feet—mapping and analyzing it, O-REx flew in close to extend its 10-foot-long sampling arm and scoop up rocks and dirt from the surface.
The spacecraft, about the size of a minivan and featuring wide solar panels extending 10 feet on each side, hovered just off the surface. When the sampling arm hit the surface, it sank in a foot.
“It was like the sample head was diving into a pit of balls at a children’s playground,” says DellaGuistina. “There was no resistance; we just kept going. And we would have kept going deeper if the spacecraft thrusters hadn’t fired in the other direction.
“We were submerged in asteroid material.”
Although all the images O-REx had sent back to NASA and Arizona scientists showed a surface that was coherent and solid, in fact the surface behaved almost like a liquid.
“I call Bennu the ‘trickster asteroid,’ ” says Dante Lauretta, DellaGuistina’s boss at the University of Arizona and the principal scientist for OSIRIS-REx. “It has challenged us every step of the way.”
How NASA is receiving more asteroid material than planned
But the loosely packed surface had an unexpected benefit. The collector stirred up so much material—enough to mostly fill a Starbucks tall coffee cup—that the sampling container overflowed. A flap designed to close the top of the container was jammed open by a pebble about an inch long. That’s why O-REx is coming home with about 250 grams of material, half a pound, instead of just 60 grams.
That dirt—sealed inside a conical return capsule designed to withstand the heat of re-entry—is unlike anything that’s ever been seen on Earth. It may well hold the secret to two of our biggest questions:
“The sample is a treasure chest from the early solar system,” says Lauretta. It will have water infused in it. It will be rich in all kinds of organic molecules. Lauretta is a Regents Professor of planetary science and cosmochemistry at the University of Arizona, the lead institution managing OSIRIS-REx with NASA. In his most extreme cosmochemistry dreams, the Bennu dirt might show some things never seen before from outer space: the precursors to life. “That would be beyond thrilling.”
Bennu is about to embark on its next mission to a second asteroid
Bennu’s mischievous nature notwithstanding, the flight of OSIRIS-REx itself has gone so well that it is swooping back to Earth with 25% of its fuel remaining. The spacecraft and its array of cameras, spectrographs, and sensors are in such good shape that 20 minutes after releasing the sample return canister to land in Utah, spacecraft controllers from Lockheed Martin in Littleton, Colorado, will tell the spacecraft to aim itself away from Earth, fire its thrusters, and head off to chase down a second asteroid.
Asteroid number two was never in the original plan. It’s a bonus mission that will last at least another six years. The spacecraft will chase down the asteroid Apophis, which is similar in size to Bennu, but of much different composition. The mission is being renamed OSIRIS-APEX. The craft can’t scoop up a sample, of course: The sample container will be back on Earth. But it can get up close as it did with Bennu.
How the mission to Bennu began
Lauretta, now 52, remembers well the day that the mission to Bennu was born. It started in the bar at the Arizona Inn, an informal after-hours hangout for the faculty of the University of Arizona, a couple blocks off campus in Tucson.
“It was February 2004,” says Lauretta. “I got this crazy phone call.” At the time, Lauretta was a 33-year-old assistant professor, and fellow planetary scientist Michael Drake asked him to meet after work at the Arizona Inn’s Audubon Bar.
“I was a young faculty member. I was just kind of wide-eyed,” says Lauretta. “Drake was the head of the Lunar and Planetary Lab. He was my boss. Three of us met at the bar”—the third person was Steve Price, from Lockheed Martin—“and we sketched out an asteroid return mission.”
The idea: Chase down an asteroid— an interesting asteroid—with a spacecraft, and then dip down, visit the surface, scoop up some of the oldest rock and dirt in the solar system, and bring it back to Earth.
Drake and Lauretta submitted a proposal for just such a mission later that year. “NASA told us, Yeah, thanks but no thanks.”
They did a second proposal. NASA said it was better. But still rejected it.
The third time, in 2011, NASA said yes, and the OSIRIS-REx mission to the comet Bennu (technically 101955 Bennu) was born.
Drake would die just months after NASA approved OSIRIS-REx, and Lauretta would become the principal investigator of the mission. Way back in 2004, when O-REx was first imagined, a freshman undergraduate named Dani DellaGuistina took a seminar on meteorites that ignited her interest in space science, a course taught by Lauretta.
These days, NASA’s space science missions—the ones without astronauts—often generate considerable excitement, especially because U.S. astronauts haven’t done much thrilling in a decade, even as the robotic missions get more daring.
The spaceship flying skills necessary for OSIRIS-REx are a good example. No one at Lockheed Martin’s mission operations center in Colorado sits in a command chair, with a joystick and a big screen. When O-REx was orbiting Bennu, it was so far from Earth that it took radio signals at least 15 minutes to get to it. Flight controllers are really sophisticated flight-dynamics computer programmers: They design a series of maneuvers to get O-REx into orbit, or to fly down and hover over the surface, and then they check those instructions, and run them through simulators—and only after many cross-checks do they beam them up as a package to the spacecraft.
When the time comes, they send an instruction telling O-REx when to execute those flight instructions. But O-REx, in fact, was so far away that it flew itself. The folks back on Earth only learned about O-REx’s adventures approaching and scooping dirt from Bennu 15 minutes or more after they had happened.
The scale of O-REx’s exploration of Bennu will only become clear after researchers unpack what’s in the dirt. But here’s a sense of what’s ahead.
What happens to the dirt from Bennu now
Two previous missions by Japan have, in fact, also returned samples from asteroids. But the largest of those samples was 5.4 milligrams. The amount of material coming home on O-REx is 50,000 times larger.
There is an elaborate plan to study it. Two hundred researchers will receive samples of the Bennu rock and dust, and they will use 60 analytical techniques to evaluate the material. “We’re going to throw everything humans can do in terms of materials science at it,” says Lauretta.
They’ll do so with one eye on the future. Those 200 scientists will only divide up 25% of the rock O-REx has brought back. Seventy-five percent of it will be sealed away by NASA to be analyzed in years to come with more sophisticated instruments that haven’t yet been created.
O-REx’s instruments have already detected the spectral signature of water on Bennu. It’s an odd kind of water, really a fourth state of water that ordinary people don’t typically encounter. Bennu is much too small—and too close to the sun—to have ice or liquid water on its surface. But what it almost certainly does have is water infused into the crystal structure of the rocks of which it is made.
That water can be released with high heat, like that from volcanic activity. In fact, the rock in Earth’s crust has similar water locked into it, and volcanoes routinely release it into the atmosphere. That kind of molecular water—delivered in asteroids—is one of the mechanisms that scientists have long hypothesized as the source for the water on Earth.
Some small quantities of the rock from Bennu will be super-heated, and the resulting water vapor collected, measured, and analyzed. Water on Earth has a particular signature: a balance between heavy-hydrogen water and regular-hydrogen water. Scientists will be looking to see if the water from Bennu matches that ratio, which would be evidence helping explain how Earth’s water arrived when the planet formed.
Just as dramatic will be the search for what kind of organic molecules are on Bennu. Other asteroid and comet samples have contained amino acids—relatively simple molecules that are the building blocks for proteins, which are the building blocks for DNA, and thus for life.
The geology of Bennu, says Lauretta, is kind of familiar. “It looks like the hydrothermal vents at mid-ocean ridges. And as we know, those are full of biology.”
How is a loosely packed 1,600-foot-wide pile of ancient black rubble like a super-hot vent at the bottom of the ocean on Earth?
There aren’t any “vents” on Bennu, Lauretta wants to make clear. “It’s geologically inert.” But scientists think Bennu broke off long ago from an asteroid that might have been 100 miles wide, and in the early days of the solar system, an asteroid that big would have accreted ice, and likely would have been heated by radiation. “Heat plus water might have produced,” exactly the kind of materials now generated at Earth’s deep ocean vents.
Could relatively simple amino acids have found a way to link into the longer chains life requires? “It would be really exciting if we saw any evidence that those amino acids had started to link together,” says Lauretta. Not DNA or RNA—which are hugely complicated—but shorter chains called peptides that make up proteins.
“That’s my dream result. Then we’re making progress toward the origin of life—which is my driving interest.
“How would those have assembled themselves? How would they have survived deep space? Those are the questions! If I knew the answers, I’d probably have a Nobel Prize.”
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