He left the ridge, walked back toward the planes. The tall stiff boots were the only things that kept him upright, and his ankles hurt. Like walking on the sea bottom, only with no resistances. Universe ocean. He reached down and dug in the dust; no bedrock for ten centimeters, then twenty; it could have been five or ten meters deep, or even more. The dustclouds he had kicked up dropped back to the surface in about fifteen seconds. The dust was so fine that in any kind of atmosphere they might have stayed in suspension indefinitely. But in the vacuum they fell like anything else. Ejecta. There simply wasn’t much to pull them back. One might be able to kick dust into space. He crossed a low ridge and abruptly could see over the sloping plain of the next facet. It was so obvious that the moonlet was shaped like some paleolithic hand tool, with facets knapped off by ancient strikes. Triaxial ellipsoid. Curious that it had such a circular orbit, one of the most circular in all the solar system. Not what you would expect of a captured asteroid, nor of ejecta flung up from Mars in one of the big impacts. Leaving what? Very old capture. With other bodies in other orbits, to regularize it. Knapp, knapp. Spall. Spallation. Language was so beautiful. Rocks striking rocks, in the ocean of space. Knocking bits off and flying away. Until they all either fell into the planet or skittered off. All but two. Two out of billions. Moon bomb. Gun stand. Rotating just faster than Mars above, so that any point on the Martian surface had it in the sky for sixty hours at a time. Convenient. The known was more dangerous than the unknown. No matter what Michel said. Clomp, clomp, on the virgin rock, of a virgin moon, with a virgin mind. The Little Prince. The planes rising over the horizon looked absurd, like insects from a dream, chitinous, articulated, colorful, tiny in the starry black, on the dust-blanketed rock. He climbed back into the lock.

• • •

It was months later, and he was alone in Echus Chasma, when the robots on Deimos finished their construction, and the starter deuterium ignited the drive engine. One thousand tons of crushed rock were thrown out by the engine every second, at a speed of 200 kilometers per second. All flying out tangent to the orbit and in the orbit plane. In four months, when about a half percent of the moon’s mass had been ejected, the engine would cut off. Deimos would then be 614,287 kilometers away from Mars, according to Sax’s calculations, and on its way completely out of Mars’s influence, to become a free asteroid again.