A near-Earth asteroid called Bennu turned out to be full of surprises — the most recent of which is the fact that it has a surface similar to a pool of plastic balls, according to NASA scientists.
The new revelation comes after the space agency successfully sampled the asteroid in October 2020.
During the historic collection event, the OSIRIS-REx spacecraft’s sampling head sank 0.5 meters into the asteroid’s surface.
Apparently, Bennu’s exterior is made of loose particles that aren’t held together very securely, based on what happened when the spacecraft took a sample.
Had the spacecraft not fired its thruster to retreat after its rapid collection of dust and rocks, it could have sunk straight into the cosmic object.
“By the time we fired our thrusters to leave the surface, we were still diving into the asteroid,” Ron Ballouz, an OSIRIS-REx scientist based at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, said in a statement. Ballouz is co-author of two studies published in July in the journals Science and Science Advances on the discovery.
Bennu is a spinning top-shaped debris pile asteroid composed of rocks held together by gravity. It is about a third of 500 meters wide.
“If Bennu were fully compacted, that would imply near-solid rock, but we found a lot of empty space on the surface,” study co-author Kevin Walsh, a member of the OSIRIS-REx science team at the Southwest Research Institute in Boulder, Colorado, said in a statement.
So what could have happened if the spacecraft’s thrusters didn’t fire right away?
“It could be that OSIRIS-REx went deeper inside the asteroid, which is both fascinating and scary,” said study co-author Patrick Michel, OSIRIS-REx scientist and research director at the Center National de la Recherche Scientifique in Côte. d. ‘Azur Observatory in Nice, France.
Fortunately, the spacecraft and its prized sample are heading back to Earth. Bennu’s sample is expected to arrive in September 2023.
Bennu defies expectations
When the spacecraft arrived at Bennu in December 2018, the OSIRIS-Rex team was surprised to find that the asteroid’s surface was covered in boulders. Previous observations prepared them for sandy, beachy terrain.
Scientists have also witnessed particles from the asteroid being launched into space.
“Our expectations about the asteroid’s surface were completely wrong,” said study author Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson, in a statement.
The spacecraft captured images of the location where it collected a sample of Bennu, which further confused the team. Although the OSIRIS-REx spacecraft very gently hit the asteroid, it lifted a huge amount of rocky debris and left a crater eight meters wide.
“What we saw was a huge wall of debris radiating from the sample site,” said Lauretta, professor of planetary science and cosmochemistry at the University of Arizona’s Lunar and Planetary Laboratory.
“We were like, ‘Damn!’ Every time we tested the sample collection procedure in the lab, we barely got any dirt.”
Before and after photos of the landing site show the difference. The images reveal what appears to be a depression in the surface, with several large boulders at its base.
The sampling event itself likely caused this sunken relief.
The asteroid’s dark surface also has more reflective dust near the collection point, showing where the rocks were moved during the event. These changes are evident in the slider below.
By analyzing the spacecraft’s acceleration data, the team determined that it encountered very little resistance, about the same amount that someone would feel pushing into a ball pit.
Understanding more about Bennu’s composition could help scientists studying other asteroids, whether it’s the goal of planning missions like OSIRIS-REx or protecting Earth from potential collisions with space rocks.
An asteroid like Bennu, barely holding together, could break apart in Earth’s atmosphere, which could pose other risks, even if it’s not a direct impact.
“We need to continue to physically interact with these bodies because this is the only way to really determine their mechanical properties and response to external actions,” Michel said. “Images are crucial, but they don’t tell us whether they are weak or strong.”
OSIRIS-REx — which stands for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer — was the first NASA mission sent to a near-Earth asteroid, and once there, performed the closest orbit of a planetary body by a spacecraft. until the moment. Bennu is the smallest object ever orbited by a spacecraft.
The memory of the Bennu spacecraft is the largest sample collected by a NASA mission since moon rocks were brought back by Apollo astronauts.
Once OSIRIS-REx approaches Earth in 2023, it will launch the capsule containing the sample, which will soar through Earth’s atmosphere and parachute into the Utah desert.
If OSIRIS-REx is still in good health after leaving the sample, it will start a new expedition to study other asteroids.
Source: CNN Brasil
