November 19, 2013
Mars, Like Earth, May Be Giving Asteroids Facelifts
Mars may be helping to shape the surface of some near-Earth asteroids, according to a new study published in the journal Icarus. Richard Binzel, a professor of planetary sciences at MIT, found in 2010 that asteroids that venture outside of the main belt in our solar system could be experiencing “asteroid quakes” as they come too close to Earth’s gravity. These quakes shift surface grains, exposing fresh grains underneath, which helps refresh asteroids.
Binzel and colleagues are now proposing that Earth may not be the only planet to thank for asteroids' younger look. The team found that Mars may be another one of the solar system’s estheticians.
For the study, researchers calculated the orbits of 60 refreshed asteroids to determine if they came close enough to Earth to experience an asteroid quake. They found 10 percent of these asteroids never crossed Earth’s orbit but instead they came very close to Mars.
“We don’t think Earth is the only major driver anymore, and it opens our minds to the possibility that there are other things happening in the solar system causing these asteroids to be refreshed,” said Francesca DeMeo, who did much of the work as a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences.
Binzel and colleagues mapped the orbits of each of the 60 asteroids in the study. They calculated the probability that an asteroid and a planet would have had a close encounter for a make-over during the last 500,000 years.
“Picture Mars and an asteroid going through an intersection, and sometimes they’ll both come through at very nearly the same time,” Binzel says. “If they just barely miss each other, that’s close enough for Mars’ gravity to tug on [the asteroid] and shake it up. It ends up being this random process as to how these things happen, and how often.”
DeMeo looked into other potential causes of asteroid refreshing by calculating the probability of asteroids colliding with each other, as well as the possibility of a phenomenon referred to as “spin-up.” She found no conclusive evidence that either event would have been significant enough to refresh asteroids, which suggests that Mars is indeed the other esthetician in the process.
“Mars is more powerful than we expected,” she said, noting the fact that Mars is a small planet to be creating quakes on 10 percent of the 60 asteroids.
“You think about these asteroids going around the sun doing their own thing, but there’s really a lot more going on in their histories,” says DeMeo, who is now a postdoc at Harvard University. “This gives you a dynamic idea of the lives of asteroids.”