We used to think moons were the boring sidekicks of the solar system. For decades, we treated them like cosmic leftovers — cold, dead rocks that did nothing but tag along with their parent planets. We ...

Far from the Sun’s heat, orbiting the outer planets of the solar system, are moons with oceans of liquid water beneath their frozen surfaces. Keith Cooper finds out how planetary scientists are ...

Moons may seem like quiet companions to the planets, but many of them are worlds every bit as fascinating as the planets themselves. Some are covered in oceans, some erupt with lava, and others hide ...