The ribbons display the path of fluid motion. Larger than average, this is the asteroid Castalia in a cutaway view. It is being hit by a house-sized rock traveling at 5 kilometers per second. The scattering white dots are fragments from the smaller rock. Researchers modeled Castalia as a peanut-shaped solid rock 1.6 kilometers long and .8 kilometers wide.
Fractures appear throughout the asteroid, with the greatest damage shown in red.
Lasting merely a second, the collision approximates the force of the Hiroshima atomic bomb. Using nuclear weapons has been proposed for breaking up, or at least diverting, asteroids headed towards Earth. The simulations show that such an impact will fracture a solid asteroid, but, later, gravity will reassemble the pieces. From Castalia we trek to our next planetary neighbor, Mars. The true global geography of the planet first emerged with comprehensive maps from Mariner 9 and Viking.