Beyond the orbit of Pluto, the planet Ronald is discovered. When scientists find out that its moon consists entirely of petroleum, an unprecedented race for the black gold ensues. On behalf of Scrooge, Donald and his nephews take off with a space ship that operates by thoughts alone, invented by Gyro Gearloose. They reach the black moon with a huge lead over all their rivals. A drop of oil which they take aboard as a sample shows unexpected proliferation and soon floods the whole ship. Fortunately Scrooge has followed them in a freighter and takes the ship-wrecked astronauts aboard. However, the petroleum is not easily shaken off.