NASA researchers have just detected water vapor in Ganymede's atmosphere.

Astronomers have discovered evidence of water vapor in the atmosphere of Jupiter's moon Ganymede for the first time.

Ganymede, the largest moon in the Solar System, is covered in an icy crust. Scientists believe Ganymede may have a liquid ocean 100 miles (161 km) beneath its surface, and that such an ocean could host aquatic alien life.