Ceres Craters and Canyons

SCIENCE CORNER

Ceres, the first discovered dwarf planet, continues to fascinate, as our “Ceres” continues…

By Dr. Marc D. Rayman

In addition to the bright spots, Dawn’s views from its present altitude have included a wide range of other intriguing sights, as one would expect on a world of more than one million square miles (nearly 2.8 million square kilometers).

There are myriad craters excavated by objects falling from space, inevitable scars from inhabiting the main asteroid belt for more than four billion years, even for the largest and most massive resident there.

Ceres craters

Several craters here have central peaks. The largest also has a ridge at the center. Note other intriguing geological structures, including the terraced walls of that crater and the contrast between the smooth area in the top half of the picture and the more rugged terrain at the bottom. The picture below overlaps the top of this view. (Photo – NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)

The craters exhibit a wide range of appearances, not only in size but also in how sharp and fresh or how soft and aged they look. Some display a peak at the center. A crater can form from such a powerful punch that the hard ground practically melts and flows away from the impact site. Then the material rebounds, almost as if it sloshes back, while already cooling and then solidifying again. The central peak is like a snapshot, preserving a violent moment in the formation of the crater. By correlating the presence or absence of central peaks with the sizes of the craters, scientists can infer properties of Ceres’ crust, such as how strong it is. Rather than a peak at the center, some craters contain large pits, depressions that may be a result of gasses escaping after the impact. (Craters elsewhere in the solar system, including on Vesta and Mars, also have pits.)

Ceres canyons

Several long canyons are evident in this view. The large crater that extends off the bottom of the picture is in the center of the picture above. Also notice the bright spots, just visible on the limb at upper left. The first picture above shows them from overhead. (Photo – NASA/JPL-Caltech/UCLA/MPS/DLR/IDA).

Dawn also has spied many long, straight or gently curved canyons. Geologists have yet to determine how they formed, and it is likely that several different mechanisms are responsible. For example, some might turn out to be the result of the crust of Ceres shrinking as the heat and other energy accumulated upon formation gradually radiated into space. When the behemoth slowly cooled, stresses could have fractured the rocky, icy ground. Others might have been produced as part of the devastation when a space rock crashed, rupturing the terrain.

Next week: Ceres’ active past.

Dr. Marc D. Rayman is the Dawn Mission Director and Chief Engineer at JPL. Marc greatly enjoys sharing the thrill of interplanetary adventures with the public.