木卫一, also known as Io, is one of the largest moons of Jupiter. It is famous for its numerous active volcanoes, making it the most geologically active body in the solar system. Io's surface is covered with sulfur and sulfur dioxide, giving it a colorful appearance. The intense volcanic activity on Io is caused by the gravitational pull from Jupiter and its other moons, which creates tidal heating. This process generates enough heat to melt the moon's interior, resulting in frequent eruptions. Io's unique features make it a fascinating subject for scientists studying planetary geology.