Thanks to some new research and computer modeling, we now understand a little more about asteroid Vesta's slightly crooked belt of massive craters.
We got our first good look at Vesta back in 2011 after NASA's Dawn probe stopped by for a visit. Images of Vesta, the second largest object in the asteroid belt, showed grooves around the asteroid that looked like a slightly crooked belt.
Although we know that a massive impact of some kind created these grooves, some of which are even bigger than the Grand Canyon, we are just learning more about what kind of collision sculpted them deep into the asteroid's surface.
"Vesta got hammered," says Peter Schultz, professor of earth, environmental, and planetary sciences at Brown University. "The whole interior was reverberating, and what we see on the surface is the manifestation of what happened in the interior."
So how do you figure out something like that? It's not like we can visit an asteroid and study it up close (although the ESA's Rosetta mission will change that when it puts a lander on the surface of an asteroid this month).
You fire a high-powered cannon here on Earth at a material that allows you to study how impacts affect it. In this instance, the cannon belongs to NASA and can fire projectiles at up to 16,000 miles per hour by using gunpowder and compressed hydrogen gas. Schultz and his colleagues used the cannon on a material called PMMA, which is a clear material that changes to point out areas of high stress. The team used a camera capable of taking a million shots per second to watch how the impact affected each part of the material.
Using that, they plugged their data into a numerical model to account for Vesta's size. Their results showed that the impact that hit Vesta happened at an angle of less than 40 degrees at around 11,000 miles per hour.
Research also showed that if the impact hit Vesta straight on, it would have broken up the asteroid completely, leaving only debris.
However, the damage to Vesta was not minor. The impact caused rocks inside the asteroid to fracture, and soon after the impact, faults creeped to the surface of the asteroid, which formed the deep crevasses that exist there today along the equator, far from the point of collision.
"When big things happen to small bodies," Schultz said, "it shakes them to the core."
[Photo Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA]
