Imaged by NASA's Dawn spacecraft, an extensive system of troughs encircles Vesta's equatorial region, with the biggest of them, called Divalia Fossa, bigger than the Grand Canyon, the space agency's Jet Propulsion Laboratory in Pasadena, Calif., reported Wednesday.
The troughs may be dropped blocks of terrain bounded by fault lines, suggesting a geologic complexity beyond that of most asteroids, researchers said.
The crustal layer at the surface appears to have stretched to the breaking point with large portions of the crust dropping down along two faults on either side of the downward-moving block, leaving the giant troughs we see today, they said.
They suggest the scale of the fracturing would only have been possible if the asteroid is differentiated, meaning that it has a core, mantle and crust.
"By saying it's differentiated," said Debra Buczkowski, a Dawn participating scientist based at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., "we're basically saying Vesta was a little planet trying to happen."