With a violent history, a watery origin, and a diameter of 256 kilometers, 2 Pallas is one seriously badass asteroid. In fact, new images of it from the Hubble Telescope have led researchers to dub it a protoplanet.
Only two bodies in the Asteroid Belt are bigger than 2 Pallas - the protoplanets 1 Ceres and 4 Vesta. And unlike a lot of other asteroids in the Belt, 2 Pallas has most likely remained unchanged since the rocky region between Mars and Jupiter first formed. Scientists speculate that 2 Pallas was originally made from "water-rich material," and that early in its history it was smashed by a massive impact that broke off a number of smaller asteroids that share 2 Pallas' rough orbit. So not only do we have a protoplanet on our hands, but it spawned a bunch of smaller asteroids too.
According to Science:
Researchers identified color variations and topography that may be linked to the asteroid's thermal evolution and to the formation of its orbital "family" – the population of asteroids that share the same orbital properties as 2 Pallas and are thought to be the fragments of a collision. In particular, a large impact crater could represent the source of the Pallas family.
Above, you can see an artist's interpretation of that impact.
Things are rough out in the Belt. But at least there's another protoplanet out there now, ready to be hollowed out and turned into a generation ship.