Half of the moon will be illuminated as it reaches its first quarter phase on Monday, June 2. The first quarter phase marks ...

Countless shadowed craters line the terminator all the way down to the moon's southern pole, while the 54-mile-wide (87 km) ...

Jupiter’s ice-covered ocean moon Europa floats above the planet’s Great Red Spot in this 1979 image from Voyager 1. This is a ...