The Institute for Creation Research

In 1610, Galileo Galilei aimed his telescope at Jupiter and discovered the four largest of the planet’s 95 known moons. He recognized them as satellites, and they became known as the Galilean moons. In order of increasing distance from Jupiter, they are Io, Europa, Ganymede, and Callisto (Figure 1). Four Warm Moons Most, if not all, of the Galilean moons show evidence of interiors that are at least fairly warm. Generally, there are three ways to warm such bodies. Leftover warmth: The moons could still be losing the energy they had at the time they formed. For scientists...