Utah: NASA's OSIRIS-REx spacecraft flung a capsule the size of a car tire onto a bombing range in Utah on Sunday, delivering safely to Earth a sample of the intriguing and potentially hazardous asteroid Bennu.
The capsule, released four hours earlier by the spacecraft, parachuted onto the muddy Utah Test and Training Range. Recovery teams in four helicopters raced to the landing site in a carefully rehearsed effort designed to bag the capsule quickly to lower the risk of contamination and then spirit it to a hangar on a military base. It will be flown Monday to the NASA Johnson Space Center in Texas for future scientific study. The main portion of the OSIRIS-REx spacecraft, meanwhile, is expected to sail on to explore yet another near-Earth asteroid, named Apophis.
Mission managers, pleased with the trajectory of the spacecraft, voted early Sunday morning to proceed with releasing the capsule, which spent four hours nearing Earth before plunging into the atmosphere. The parent spacecraft then fired thrusters to ensure that it would not wind up in Utah, but would instead move on to another target, the asteroid Apophis, with a scheduled encounter in 2029.
Why did NASA send a spacecraft to sample the asteroid Bennu?
First, there's the scientific reason. This is a small step toward answering a fundamental question: "Why are we here?"
Bennu contains rocks that date to the earliest epoch of the solar system. The mission is designed to give scientists samples of these "fossils" that date back 4 billion years. The molecular makeup of the material brought back to Earth could provide clues to how it became an ocean planet, with the kind of environment where life could appear (and eventually evolve into complex organisms such as astrobiologists).
Although NASA has never previously sampled an asteroid, a mission led by Japan's space agency, Hayabusa2, brought back samples in 2020 of a different, and much larger, asteroid called Ryugu.
Beyond the science, there's the issue of planetary defense. Bennu could spell trouble. Its orbit crosses Earth's, and there is a small chance it could hit us some time in the coming centuries. NASA keeps track of such "near-Earth objects" (including comets) that might pose collision risks, and right now Bennu is at the top of NASA's list of potentially hazardous space rocks.
It is not the biggest asteroid out there, but its problematic orbit justifies keeping a close eye on it.
NASA's DART mission last year demonstrated that it is possible to fly a spacecraft into an asteroid and change its motion. The space agency would still like to know more about the composition of these dangerous near-Earth objects and how they might potentially be diverted, which is part of what scientists will study using the sample from Bennu.
NASA wants this done quickly and carefully to avoid any contamination of the sample with desert sands, skewing test results.
On Monday the sample is to be flown by plane to NASA's Johnson Space Center in Houston. There, the box will be opened in another "clean room."
NASA plans to announce its first results at a news conference October 11.
Most of the sample will be conserved for study by future generations. Roughly one-fourth will be immediately used in experiments, and a small amount will be sent to mission partners Japan and Canada.
Japan had earlier given NASA a few grains from asteroid Ryugu, after bringing 0.2 ounces of dust to Earth in 2020 during the Hayabusa-2 mission. Ten years before, it had brought back a microscopic quantity from another asteroid.
But the sample from Bennu is much larger, allowing for significantly more testing, Simon said.
When might Bennu collide with Earth?
Not soon. Not in anyone's lifetime, unless human longevity changes dramatically. In fact, it might never hit Earth. But in 2182, it has a roughly 1 in 2,700 chance of impacting our planet, according to a calculation published in 2021. That calculation will be refined after Bennu makes a close pass by Earth in 2135.
How big is Bennu?
The asteroid has a diameter of 500 meters (about 1,640 feet). That's not nearly as big as the object that hit Earth 66 million years ago and closed the book on dinosaurs (other than the ones we call birds). But if Bennu hits Earth, that will be a bad day.
What did OSIRIS-REx collect?
The sampler device at the end of a robotic arm of the spacecraft plunged into Bennu's surface about 20 inches deep and emerged with a mixture of material known as regolith. How much is in the sample, exactly, is unknown. Some spilled during the maneuver, but mission leaders believe they have about 250 grams (about 8.8 ounces) of material, plus or minus 101 grams. To meet the mission's stated goal, there needs to be at least 60 grams in the capsule.
Is the OSIRIS-REx mission officially a success?
This was a triumph of aerospace engineering. The technical challenges were immense, including the complexities of guiding a spacecraft into orbit around a small object many millions of miles away.
It is not possible to joystick such maneuvers, so the spacecraft had to function autonomously as it carried out the delicate sampling operation on the asteroid's surprisingly rough, boulder-strewn surface. Until the spacecraft got close to Bennu, no one realized the degree to which it was just a loosely aggregated "rubble pile."
Now comes the science. Success may ultimately be defined by what, exactly, scientists learn from the Bennu bits once they can study them in the lab.
What is the coolest word used by scientists who study things like asteroids and planets?
"Ephemeris." NASA defines it as "a tabulation of computed positions and velocities (and/or various derived quantities such as right ascension and declination) of an orbiting body at specific times." Plural: ephemerides.
Why is the mission called OSIRIS-REx?
Because the acronym is much easier to say than the full name, which is Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer. Osiris is the name of an ancient Egyptian god, and Dante Lauretta, the lead scientist on the mission, is a mythology buff who thought the name would work well. Now that the spacecraft has a new target, OSIRIS-REx has been renamed OSIRIS-APEX, for OSIRIS-Apophis Explorer.
They "can give us clues about how the solar system formed and evolved," said Osiris-Rex program executive Melissa Morris.
"It's our own origin story."
By striking Earth's surface, "we do believe asteroids and comets delivered organic material, potentially water, that helped life flourish here on Earth," Simon said.
Scientists believe Bennu, about 500 meters (1,640 feet) in diameter, is rich in carbon - a building block of life on Earth - and contains water molecules locked in minerals.
Bennu surprised scientists in 2020 when the probe, during its brief contact with the asteroid's surface, sank into the soil, revealing an unexpectedly low density, like a children's pool filled with plastic balls.
Understanding its composition could come in handy in the - distant - future.
For there is a slight, but non-zero, chance (one in 2,700) that Bennu could collide catastrophically with Earth, though not until 2182.
But NASA last year successfully deviated the course of an asteroid by crashing a probe into it in a test, and it might at some point need to repeat that exercise - but with much higher stakes.
