Where's the Kaboom?

Here. Once Curiosity was safe on the Martian surface, the cable it was lowered on was severed, and the descent stage was programmed to fly away to the northwest of the landing site, selected because this took it away from the locations of greatest interest to NASA. It hit the surface about 650 meters from Curiosity, traveling at about 160 Kilometers an hour, probably with significant residual Hydrazine rocket fuel still in its tanks.

It was probably something of a Michael Bay moment, with a dramatic fireball and the descent stage scattered into pieces not much larger than a foot in diameter.