THAT THESE DROP PODS WERE OF MILITARY DESIGN WAS OBVIOUS from the way they came in: fast. Each had a set of vanes, mounted near the top, that sprang out when it was a couple of thousand meters above the surface, slowing its fall. But not until the pod was just a few tens of meters above the ground did its retro-rockets come on: not just one but a circular array of thumb-sized solids that created a cylindrical piston of fire on which the pod eased to a stop, coming to light on a tripod of buglike legs that deployed themselves at the last possible moment and absorbed the shock of contact.