“What smacks into Ceres, stays on Ceres,” suggests a study from Brown University published in Geophysical Research Letters. Using high-velocity impact experiments, the scientists aimed to explain what happens when objects crash on the curiously soft surface of the dwarf planet.
Ceres, named after the Roman goddess of Agriculture, is the largest object in the asteroid belt and the closest dwarf planet to the Sun. Ceres was reached by the space probe Dawn early this year; the images we received show an undistinguished surface, not at all what was expected for an object that must have experienced billions of years of meteoritic bombardment.
“It’s really bland in the telescopic observations,” said Daly, a PhD student at Brown and the study’s lead author in a statement. “It’s like someone took a single color of spray paint and sprayed the whole thing. When we think about what might have caused this homogeneous surface, our thoughts turn to impact processes.”
Surface observations and density estimations suggest that Ceres is either made of porous silicate material or has a subterranean layer of ice. To test the possible scenarios that led to the surface we see today, the researchers used the NASA’s Ames Vertical Gun Range, a 4.3-meter (14-foot) barrel cannon that can launch projectiles at up to 26,000 kilometers per hour (16,000 miles per hour).
To simulate the surface, the team used pumice analogous of the porous silica scenario, and snow (pure and with a veneer of silicate) as an equivalent to the icy case. The projectiles were pebbles made of either basalt or aluminum, counterparts for stony and metallic meteorites. The velocity generated by the cannon was consistent with the expected typical velocity of impactors in the asteroid belt.
The experiment highlighted that if Ceres is ice-rich, it might accrete, or accumulate, non-native material more efficiently, retaining up to 77% of the impactor’s mass in or around the crater. Detailed images of Ceres' surface, currently being taken by Dawn, could attest if this experiment is a good case study for the dwarf planet.
If this hypothesis turns out to be correct, then Ceres may have accumulated a significant amount of material since its formation at the birth of the Solar System.