Allenby, in command of the Mars I, was first to set foot outside the ship. He took his "one small step for man" -- and found himself staring at the rock in front of him. It was about five feet high. Ordinary granite -- no special shape -- and several inches below its summit, running straight through it in a northeasterly direction, was a neatly round four-inch hole.He made a pun and grunted."Well, I'll be," said Janus, our photographer. "A hole.""In a rock," added Gonzales, our botanist."Round," said Randolph, our biologist."An artifact," finished Allenby softly.Before we were done we'd found similar holes all over the surface of the planet.