木卫三, also known as 欧罗巴, is one of the largest moons of 木星. It is the sixth-largest moon in the solar system and is primarily composed of water ice and rock. Its surface features a smooth, icy crust with many cracks and ridges, suggesting geological activity beneath. Scientists are particularly interested in 木卫三 because it is believed to have a subsurface ocean beneath its icy surface. This ocean may contain more than twice the amount of water found on Earth, making 木卫三 a prime candidate in the search for extraterrestrial life within our solar system.