“Gee, we’d like to look after him!” Steve answered. “If you take him outside on Callisto, you’ll have to put him in that air-tight cage over there I had made. It’s sort of like a space suit for him.” Sue and Steve played with Bud in the room they used for games until it was time to “strap down” for landing. Then they went to the couch hall and lay down on cots like the other space travelers were doing. They buckled straps across their bodies to keep them in place. For a long time, Steve and Sue lay there as the big freighter began cutting its rushing speed. It felt to Steve as if a giant anvil were crushing downward on his chest. Take-off and landing were always the roughest moments in space travel, as the twins had already found out on other space trips. At last the ship set down on Callisto. The young Shannons went back to the game room. Then with the bird on Steve’s shoulder, the twins looked out the window at the strange new world. They saw a land bathed in ghostly twilight. Very little light was coming from the sun. It was so far away that it was only a small circle. Most of the light came from a huge shape that looked like somebody’s lost beach ball resting on the ground. Its bottom edge just touched the horizon. Sue and Steve were joined by their father, who worked for the space freight company. “That’s His Majesty, Jupiter—the king of planets,” Mr. Shannon told them. “He’s over a million miles away and yet he looks close enough to touch, doesn’t he?” “Let’s go outdoors, Dad!” Steve begged. “No reason why we can’t,” Mr. Shannon replied. After they had put on their space clothes, Steve popped Bud into his warm, air-tight cage. As they all went outside, they saw the crewmen unloading the cargo. “There’s the colony over there,” Mr. Shannon said, pointing to a high framework that looked something like an oil derrick. “They mine here for a mineral called magna. It’s very valuable, because without it we couldn’t have atomic engines. Magna is what keeps our rocket tubes from melting under the terrific heat that goes through them.” “May we go down into the mines, Dad?” Steve asked. “We’ll see if we can,” said his father. As they walked toward the mining place, Mr. Shannon said, “Underneath us are pockets of poisonous gas like that found in Jupiter’s atmosphere. Sometimes it leaks into the mining tunnels causing danger from suffocation.” “I sure hope the gas stays where it belongs while we’re down there!” Steve said and swallowed the lump of fear in his throat. They turned their attention to Jupiter. It looked even more like a beach ball now with its stripes of beautiful colors. Mr. Shannon said the bands were floating ice bergs of the poisonous gases he was talking about. “No ship can land on Jupiter,” he said. “Its gravity would crush a spaceman flat. Gravity pull is much stronger on the larger planets, you know. Jupiter’s atmosphere is many thousands of miles deep. Raging storms are going on beneath it all the time.”