HONOLULU — Clumps of craters on Ceres hint at a surprising past for the dwarf planet. Whether that past involves hidden ice deposits, a devastating whack by another space rock or something else entirely is uncertain.
“There is clearly something funky going on,” Simone Marchi of the Southwest Research Institute in Boulder, Colo., reported August 3 at a meeting of the International Astronomical Union.
Some regions of Ceres have more craters than others. Maps created by the Dawn spacecraft, in orbit around Ceres since March (SN: 4/4/15, p. 9), show that areas with the fewest craters overlap regions surrounding the three largest craters, two of which are nearly 300 kilometers across.
The terrain in and around one of these craters, dubbed Kerwan, is quite smooth and flat, said Marchi. This landscape appears to be no older than 1 billion years. “That’s relatively fresh and young by geological standards,” he said. Ceres, after all, has been around for about 4.6 billion years.
Shifting pockets of ice just beneath the surface on Ceres could put a little more spring into the overlying terrain, eroding the oldest craters. If the ice turns to vapor, the ground above might collapse and smooth over, as it does on some moons of the outer planets. Or perhaps Ceres suffered a cataclysmic blow that swept clean some of its terrain.
After just a few months of surveying by Dawn, Ceres is already shaping up to be a surprising world. “At first glimpse it looks like any other asteroid,” said Marchi. “It is not.”