This could have implications for how the LHB affected the solar system, Pirani pointed out. Our best models from it come from looking at our nearby moon, but the LHB may have acted differently inside the main asteroid belt, where Vesta resides.
PHOTO: Asteroid Vesta Up Close
Vesta is one of only a handful of small solar system bodies to be looked at up close. Ceres, where Dawn is orbiting right now, is a dwarf planet with a completely different surface. The ice suspected to lie there, for example, likely causes evidence of craters to erase quite quickly, Pirani said. As for how the erasing took place on Vesta, there are at least a couple of mechanisms that could have caused it, Pirani wrote.
"A possible resurfacing process that could have contributed to erase LHB craters is the wide spread ejecta blanketing, for example. The bigger a target body is, the more ejecta are expected to be retained on its surface after an impact that could affect older craters in the neighborhood," Pirani said.
"Another process to take into account is the seismic shaking following an impact. Vesta showed two big impact basins on the south pole, so the seismic shacking could have been an important mechanism of resurfacing."
BIG PIC: Protoplanet Vesta's Coat of Many Colors