Rip left his feet with a little spring and shot through the door. Directly below him, the asteroid gleamed darkly in the light of the tiny sun. His first reaction was "Great Cosmos! What a little chunk of rock!" But that was because he was used to looking from the space platform at the great curve of Terra or at the big ball of the moon. Actually the asteroid was fair-sized, when compared with most of its kind. The Planeteers hauled themselves into the boats by their safety lines. Rip waited until all were in, then pulled himself along his own line to the black square of the door. Koa was waiting to give him a hand into the craft. The Planeteers were standing, except for Dowst. Rip had never seen an old-type railroad, or he might have likened the landing boat to a railroad boxcar. It was about the same size and shape, but had huge "windows" on both sides and in front of the pilot--windows that were not enclosed. The space-suited men needed no protection. "Blast," Rip ordered. A pulse of fire spurted from the top of each boat, driving them bottom first toward the asteroid. "Land at will," Rip said. The asteroid loomed large as he looked through an opening. It was rocky, but there were plenty of smooth places. Dowst picked one. He was an expert pilot, and Rip watched him with pleasure. The exhaust from the top lessened, and fire spurted soundlessly from the bottom. Dowst balanced the opposite thrusts of the top and bottom blasts with the delicacy of a woman threading a needle. In a few moments the boat was hovering a foot above the asteroid. Dowst cut the exhausts, and Rip stepped out onto the tiny planet. The Planeteers knew what to do. Corporal Pederson produced hardened steel spikes with ring tops. Private Trudeau had a sledge. Driving the first spike would be the hardest, because the action of swinging the hammer would propel the Planeteer like a rocket exhaust. In space, the law that every action has an equal and opposite reaction had to be remembered every moment. Rip watched, interested in how his man would tackle the problem. He didn't know the answer himself, because he had never driven a spike on an airless world with almost no gravity, and no one had ever mentioned it to him. Pederson searched the gray metal with his torch and found a slender spur of thorium, perhaps two feet high, a short distance from the boat. "Here's a hold," he said. "Come on, Frenchy. You too, Bradshaw." Trudeau, carrying the sledge, walked up to the spur of rock and stood with his heels against it. Pederson sat down on the ground with his legs on either side of the spur. He stretched, hooking his heels around Trudeau's ankles, anchoring him. With his gloves, he grabbed the seat of the Frenchman's space suit.