BY JUPITER

Two decades later, Galileo found a moon transformed, its surface remodeled by unrelenting volcanic activity. This seething volcanism is thought to be caused by the massive tides wrought by nearby Jupiter: The push and pull heats and liquefies the mantle of little Io, no bigger than Earth's moon. Meanwhile, science fiction remains more stable: Star Trek: Insurrection is on screens worldwide, and Alien vs. Predator, the computer game, is released.