"I don’t know exactly," he admitted. "But from the ship’s actions, I’d say we were aiming for the far side of the asteroid belt. Anyway, we’ll fall short of Jupiter." There was a glimmer of respect in O’Brine’s glance. "That’s right. Know anything about asteroids, Foster?" Rip considered. He knew what he had been taught in astronomy and astrogation. Between Mars and Jupiter lay a broad belt in which the asteroids swung. They ranged from Ceres, a tiny world only 480 miles in diameter, down to chunks of rock the size of a house. No accurate count of asteroids—or minor planets, as they were called—had been made, but the observatory on Mars had charted the orbits of over 100,000. Most of them were only a mile or two in diameter. Others, much smaller, had never been charted by anyone. One leading astronomer had estimated that as many as 50,000 asteroids filled the belt. "I know the usual stuff about them," he told O’Brine. "I haven’t any special knowledge." O’Brine blinked. "Then why did they assign you? What’s your specialty?" "Astrophysics." "That might explain it. Second specialty?" "Astrogation." He couldn’t resist adding, "That’s what scientists call space navigation, Commander." O’Brine started to retort, then apparently thought better of it. "I hope you’ll be able to carry out your orders, Lieutenant," he said stiffly. "I hope, but not much. I don’t think you can." Rip asked, "What are my orders, sir?" O’Brine waved in the general direction of the wall. "Out there, somewhere in the asteroid belt, Foster, there is a little chunk of matter about one thousand yards in diameter. A very minor planet. We know its approximate coordinates as of two days ago, but we don’t know much else. It happens to be a very important minor planet." Rip waited, intent on the commander’s words. "It’s important," O’Brine continued, "because it happens to be pure thorium." Rip gasped. Thorium! The rare, radioactive element just below uranium in the periodic table of the elements, the element used to power this very ship! "What a find!" he said in a hushed voice. No wonder the job was Federation priority A, with Space Council security! "What do I do about it?" he asked. O’Brine grinned. "Ride it," he said. "Your orders say you’re to capture this asteroid, blast it out of its orbit, and drive it back to earth!" CHAPTER FOUR - FIRST, FIND THE NEEDLE! Rip walked into the squadroom with a copy of the orders in his hand. After one look at his face, the Planeteers clustered around him. Santos woke those who were sleeping, while Rip waited. "We have our orders, men," he announced. Suddenly he laughed. He couldn’t help it. At first he had been completely overcome by the responsibility, and the magnitude of the job, but now he was getting used to the idea and he could see the adventure in it. Ten wild Planeteers riding an asteroid! Sunny space, what a great big thermo-nuclear stunt!