As corn kernels pop into a frying pan, tiny specks of dust can slosh around on the surface of asteroids, according to a new study by physicists at the University of Colorado Boulder.
The popcorn-like effect could also help clean up smaller asteroids, causing them to lose dust and look rough and fuzzy from space.
The researchers published their results in the journal Nature Astronomy. Study lead author Hiang-wen (Sean) Soo said their findings could help scientists better understand how asteroids change shape over time—and how these bodies migrate through space, sometimes at times. bring them dangerously close to Earth.
“The more fine-grained material, or regolith, these asteroids lose, the faster they migrate,” said Hsu, a research associate in the Laboratory of Atmospheric and Space Physics (LASP) at CU Boulder.
The research began with some curious photographs.
In 2020, a NASA The spacecraft, named OSIRIS-REx, traveled more than 1 billion miles to rendezvous with asteroid (191055) Bennu, which is as tall as the Empire State Building. But when the spacecraft arrived, scientists didn’t get what they were hoping for: The asteroid’s surface looked like rough sandpaper, not as smooth and dusty as the researchers had predicted. Large stones were also scattered on its exterior.
Now, Sue and her colleagues have drawn on computer simulations, or models, and laboratory experiments to explore that puzzle. He said forces similar to static electricity can kill the tiniest particles of dust, some no larger than a bacterium, from an asteroid and into space – leaving only large rocks behind.
Study co-author Mihaly Horani said Bennu is not alone.
“We are realizing that the same physics is happening on other airless bodies like the Moon and even Saturn’s rings,” said Horani, a LASP researcher and professor of physics at CU Boulder.
Bennu and Ryugu
Asteroids may look like they have frozen over time, but these bodies evolve throughout their lifetime.
Sue explained that asteroids like Bennu are constantly rotating, exposing their surfaces to sunlight, then shadow and sunlight. This never-ending cycle of heating and cooling exerts pressure on the largest rocks at the surface, until they inevitably break.
“It’s happening every day, all the time,” Sue said. “You break a big piece of rock into smaller pieces.”
This is why, before scientists reached Bennu, many expected it to be covered with smooth sand.,Something similar to what the moon looks like today. Not long ago, a Japanese space mission landed on another small asteroid named Ryugu. The team got a similar rough and rough terrain. Sue and her companions became suspicious.
Since the 1990s, LASP researchers have used vacuum chambers in the laboratory to investigate the strange properties of dust in space, including a feat they call “electrostatic lofting.” Xu Wang, co-lead author of the study, explained that as the sun’s rays bathe the tiny particles of dust, they begin to take on a negative charge. Those charges would build up until, suddenly, the particles explode, like two magnets repelling each other.
In some cases, those grains of dust can travel away at speeds of up to 20 miles per hour (or more than 8 meters per second).
“This process has never been observed before on the surface of an asteroid,” said Wang, a research associate at LASP.
small asteroid big asteroid
To do this, researchers including former CU Boulder graduate students Anthony Carroll and Noah Hood ran a series of calculations probing the physics of regolith on two hypothetical asteroids. They tracked how the dust might have formed, then hopped over hundreds of thousands of years. One of those impure asteroids was about half a mile (similar in size to Ryugu) and the other several miles wide (closer in diameter to larger asteroids like Eros).
There was a difference in size. According to the team’s estimates, when the dust particles hit the large asteroid, they could not gain enough speed to break free from its gravity. This was not the case even on the smaller, Ryugu-like asteroid.
“The gravity on the small asteroid is so weak that it can’t stop the escape,” Sue said. “Fine regolith will be lost.”
That lost dust, in turn, would expose the asteroid’s surface to even more erosion, creating boulder-rich sequences like those found on Ryugu and Bennu. Within several million years, in fact, the small asteroid was almost completely cleared of fine dust. However, an asteroid like Eros remained dusty.
Sue said this scrubbing effect could help give the orbits of smaller asteroids a nudge. He explained that asteroids migrate because the Sun’s radiation slowly pushes on them over time. Based on previous research from other scientists, they suspect that asteroids covered in boulders may be moving faster than dusty-looking ones.
He and his colleagues may soon have more evidence to support their calculations. In less than 3 months, a NASA mission called the Double Asteroid Redirection Test (DART) will visit a pair of smaller asteroids—and Hsu will look to see how dusty they are.
“We will have new surface images to test our theory,” he said. “It’s good for us, but also a little nervous.”