Europa's icy surface is relatively smooth and has distinctive linear ridges, cracks and flows. Many scientists believe that liquid water oceans may lie beneath this outer ice layer, making Europa a place where life could exist.
Photo: Europa taken by the Galileo probe (NASA)
Jupiter's smooth moon may have subsurface oceans.
Images of Jupiter's moon reveal evidence of a new type of volcanism.
Images from the Galileo and Voyager missions (launched in 1989 and 1977 respectively) showed scientists that Europa is a relatively smooth icy moon with a network of fractures that may erupt liquid water from an ocean beneath the surface.
Voyager opens up the question of whether life could exist on Jupiter's moon.
The Voyager probe pictures of Jupiter's moon Europa showed scientists that the satellite's ice surface is relatively smooth and covered with linear features. They theorised that an ocean of liquid water exists below the surface and that this fluid might contain life that gets its energy from the moon's inner heat.
As the Sun ages, Europa will warm and may support life.
Jupiter's moon Europa will warm as the Sun ages and may support life. Scientists speculate it could become a watery world.
Jupiter's moons aren't the cold, dead worlds the experts expected.
Voyager scientists thought Jupiter's moons would be cold, dead worlds. They were amazed when the first close-up images from the spacecraft revealed four moons, each different from the next. The probes were launched in 1977.
If life can exist in solid ice on Earth, what about Europa?
Professor Brian Cox goes to caves in Iceland to find microbial life that survives in solid ice. Astrobiologists theorise that if life can live in solid ice on Earth, it may be able to survive on Jupiter's icy moon Europa
Europa i/jʊˈroʊpə/ (Jupiter II), is the sixth-closest moon of the planet Jupiter, and the smallest of its four Galilean satellites, but still the sixth-largest moon in the Solar System. Europa was discovered in 1610 by Galileo Galilei and possibly independently by Simon Marius around the same time. Progressively better observations of Europa have occurred over the centuries by Earth-bound telescopes, and by space probe flybys starting in the 1970s.
Slightly smaller than the Moon, Europa is primarily made of silicate rock and probably has an iron core. It has a tenuous atmosphere composed primarily of oxygen. Its surface is composed of water ice and is one of the smoothest in the Solar System. This surface is striated by cracks and streaks, whereas craters are relatively rare. The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath it, which could conceivably serve as an abode for extraterrestrial life. This hypothesis proposes that heat from tidal flexing causes the ocean to remain liquid and drives geological activity similar to plate tectonics. On 8 September 2014, NASA reported finding evidence confirming earlier reports of plate tectonics in Europa's thick ice shell - the first sign of such geological activity on another world other than Earth.
In December 2013, NASA reported the detection of "clay-like minerals" (specifically, phyllosilicates), often associated with "organic material" on the icy crust of Europa. In addition, NASA announced, based on studies with the Hubble Space Telescope, that water vapor plumes were detected on Europa and were similar to water vapor plumes detected on Enceladus, moon of Saturn.
The Galileo mission, launched in 1989, provided the bulk of current data on Europa. No spacecraft has yet landed on Europa, but its intriguing characteristics have led to several ambitious exploration proposals. The European Space Agency's Jupiter Icy Moon Explorer (JUICE) is a mission to Europa that is due to launch in 2022. NASA is planning a robotic mission that would be launched in the "mid-2020s".