For the first time, astronomers have uncovered evidence of water vapor in the atmosphere of Jupiter's moon Ganymede.
This water vapor forms when ice from the moon's surface sublimates - that is, turns from solid to gas.
Details
Previous research has offered circumstantial evidence that Ganymede, the largest moon in the solar system, contains more water than all of Earth's oceans.
However, temperatures there are so cold that water on the surface is frozen solid.
Ganymede's ocean would reside roughly 100 miles below the crust; therefore, the water vapor would not represent the evaporation of this ocean.