In October 2020, a small spacecraft briefly touched an asteroid to grab a piece of it to bring it to Earth. Nearly two years later, scientists have learned that if the OSIRIS-REx spacecraft had extended its stay even a little further, it would have sunk directly into the asteroid.
This is because the asteroid Bennu is nothing as scientists had predicted. Instead of being a solid, flying rock, Bennu is made up of small, pebble-like particles that are not strongly bonded together, creating a lot of space on its surface. It is more comparable to a well of plastic balls, writes NASA in a new release. “Our expectations about the asteroid’s surface were completely wrong,” Dante Lauretta, principal investigator at OSIRIS-REx and lead author of a recent article detailing the findings, said in the statement.
OSIRIS-REx arrived on the asteroid in December 2018 with the mission to retrieve a sample of Bennu and take it to Earth for analysis. The spacecraft landed on Bennu in October 2020, extending its robotic arm to grab a piece of the asteroid. The OSIRIS-REx immediately fired its thrusters to move away from Bennu. The spacecraft’s sampling head touched Bennu’s surface for about 6 seconds before retreating. By stirring some of the asteroid’s dust and pebbles, OSIRIS-REx was able to grab a couple of ounces of material.
Collection of OSIRIS-REx samples on the asteroid Bennu: Vista SamCam by TAGSAM
The brief encounter left a great impression on Bennu, resulting in a chaotic explosion of pebbles and an 8-meter-wide crater. “Every time we tried the sample collection procedure in the lab, we barely made a divot,” Lauretta said. But after reviewing the images from the actual sample collection, the scientists were confused. “What we saw was a huge wall of rubble radiating from the sample site,” Lauretta said. “We were like, ‘holy cow!'”
After analyzing the volume of debris seen in the images before and after the landing site, the scientists learned that OSIRIS-REx faced as much resistance to touching the asteroid as “a person would feel as he pressed the ‘plunger of a French press’. coffee bottle, “NASA wrote in a statement. That is, the spacecraft encountered very little resistance, certainly not the kind of resistance that would be expected to land on a rocky body. When the spacecraft fired its propellers to go, it was sinking into the asteroid.
“If Bennu were completely full, that would involve an almost solid rock, but we found a lot of empty space on the surface,” said Kevin Walsh, a member of the OSIRIS-REx scientific team and lead author of a second article on the composition of Bennu. he said in a statement.
When OSIRIS-REx first arrived on the asteroid, close-up images of Bennu revealed that its surface was full of blocks, rather than the smooth surface of sand that had been predicted. The images also showed that Bennu was spitting pebbles into space. “I think we’re still in the early stages of understanding what these bodies are, because they behave in a very counterintuitive way,” Patrick Michel, an OSIRIS-REx scientist, said in a NASA statement.
Bennu has been full of surprises. One of the first was his strange shape, resembling the deception of a child.