When NASA’s OSIRIS-REX spacecraft touched the surface of an asteroid on Tuesday to gather a sample of rocks and dirt, the operation proceeded smoothly, to the glee of the mission’s operators 200 million miles away on Earth.
But the biggest question remained unanswered: How much of the asteroid did OSIRIS-REX pick up? Did it manage to gather any samples at all?
On Wednesday, the mission managers released a video of the sampling mechanism hitting the surface of the asteroid, within three feet or so of where the spacecraft had been aimed.
“I must have watched about a hundred times last night,” Dante Lauretta, the principal investigator of the mission, said during a news conference on Wednesday.
The sampling mechanism set down partly on a rock about 8 inches wide. That could have caused a problem if it had prevented the mechanism from pressing up against the surface.
“But literally, we crushed it,” Dr. Lauretta said. “When the spacecraft made contact, that rock appears to fragment and shatter, which is great news.”
A burst of nitrogen gas kicked up a cloud of rocks and dirt, as hoped.
“You can see that particles are flying all over the place,” Dr. Lauretta said. “We really did kind of make a mess on the surface of this asteroid, but it’s a good mess.”
The chances that spacecraft captured a sizable sample “have gone way, way up,” he said.
It will still be a few days before scientists can confirm how much material was trapped within the sample collector, which resembles an automobile air filter.
On Thursday, the spacecraft will take photographs of the collection mechanism, which may show some of the asteroid soil stuck to velcro-like surfaces. On Saturday, it will conduct a pirouette to estimate how much material has been trapped inside.
“There’s an incredibly clever physics experiment that the team has designed here called the sample mass measurement,” Dr. Lauretta said during the NASA Television broadcast on Tuesday.
The robotic arm with the sample collector at the end will be extended and then the spacecraft will be nudged into a spin on Saturday. “We’re measuring a property called the moment of inertia,” Dr. Lauretta said.
The scientists will compare the rate of spin to what they measured before collecting a sample. Just as a skater with outstretched arms holding a barbell would spin slower than a skater holding nothing, OSIRIS-REX will spin slower depending on how much material was picked up.
The calculation of the collected mass is to be completed by Monday. Dr. Lauretta said if the measurement shows more than 80 grams, or almost 3 ounces, that would be enough. Scientists are hoping for at least a couple of ounces, but it could be more than four pounds.
If by unlucky chance OSIRIS-REX came up short on Tuesday, it can try two more times. The next attempt would be at a backup site named Osprey in January.
The collection of the asteroid sample is the climax of the $800 million mission, which launched four years ago. The spacecraft has been making detailed observations of Bennu — a rock as wide as the Empire State Building is tall — for two years, mapping features of its surface as small as a couple of inches wide. It even discovered that Bennu was shooting debris from its surface into space.
The mission’s controllers selected a spot inside a crater near Bennu’s north pole that they named Nightingale. The spacecraft, 20 feet wide and about the size of a sport utility vehicle, had to navigate carefully to the target site, which is only 26 feet in diameter. In addition, it had to avoid a wall of rocks on the eastern edge of the crater. That included a pointy pillar nicknamed Mount Doom, which is as tall as a two- or three-story building.
However, despite the risks, Nightingale offered the greatest potential scientific payoffs, with unobstructed fine-grained material that appears to contain carbon-rich minerals.
Asteroids, mostly located in orbits between Mars and Jupiter, are bits that never coalesced into a planet, and planetary scientists hope that the samples from Bennu could shed light on what the young solar system was like when it formed 4.5 billion years ago. Asteroids like Bennu, which possesses carbon-rich minerals, may have provided the building blocks for life to arise on Earth.
The asteroid is also being studied because its orbit could cause it to collide with Earth late in the 22nd century. The likelihood of such an occurrence is low, and the asteroid is not large enough to end human civilization should it occur.
OSIRIS-REX — the name is a shortening of Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer — is to leave the asteroid next year and drop off the sample, which will parachute to a landing in Utah on Sept. 24, 2023.