But considering how pervasive life is on Earth, few scientists are willing to rule out the possibility. Not everyone agrees that there's an ocean beneath Europa's ice, though. That's because scientists have some very different ideas on the age of Europa's surface. Europa itself is about four and a half billion years old. But its surface is younger.
Some scientists say it's as much as two or three billion years old.
Europa has relatively few impact craters on its surface, indicating that the surface changes quickly. That's a good sign that the ice is floating atop liquid water.