Life on Europa?

In 1995, NASA's Galileo probe entered orbit around Jupiter and began studying the gas giant and its moons: Ganymede, Callisto, Io and Europa.

The mission soon made ice-covered Europa its main focus, however, as scientists speculated about a vast liquid ocean hidden beneath the moon's icy shell.

Where there's water, there's probably life, they said. But just what kind of life?