Life is a Highway (of Flying Space Rocks)

It has been a great week for humans banging on things around the solar system. Japan's Hayabusa2 probe touched down and grabbed a sample of asteroid Ryugu; NASA's InSight is hammering into the surface of Mars; and a private Israeli spacecraft named Beresheet is heading toward an April landing on the Moon. But we are just beginners at the game. Nature has been banging and moving things around in the solar system for billions of years--and doing it with impressive efficiency. Case in point: