Discovering Europa: An Ocean Moon

Europa, first observed by Galileo Galilei in 1610, is one of the largest of Jupiter's 79 moons. It is unique among them for its smooth, icy surface, hinting at a subsurface ocean.

Beneath Europa's icy crust, which is up to 30 kilometers thick, lies a salty liquid water ocean. It is estimated to be over 100 kilometers deep - deeper than Earth's oceans, holding twice as much water.

Europa's ocean could harbor life. It contains the key ingredients: water, chemistry, and energy sources from tidal heating and possibly underwater hydrothermal vents, similar to those on Earth.

Europa's surface is crisscrossed by a pattern of ridges and fractures. These may be caused by the tidal forces exerted by Jupiter's gravity, indicating geologic activity below.

NASA's upcoming Europa Clipper mission, slated for the 2020s, aims to closely study Europa's surface and subsurface, seeking signs of habitability. Its payload includes ice-penetrating radar to explore beneath the crust.

Europa has a tenuous atmosphere composed mostly of oxygen. However, this oxygen isn't from biological processes but is generated by solar radiation and charged particles hitting the icy surface.

Exploring Europa is challenging due to extreme radiation from Jupiter's magnetic field. Electronics must be shielded, and mission durations are limited to reduce radiation damage to spacecraft.