The sharpest ever image of Europa’s full disk, captured by NASA’s Galileo mission in 1990 (Image Credit: NASA/JPL-Caltech/SETI Institute)
Europa is the fourth largest moon of Jupiter, trailing the three other Galilean satellites: Io, Ganymede, and Callisto. This moon holds the title for having the smoothest surface in the entire solar system, covered in bright ice crisscrossed by blue and red cracks and ridges that can be seen stretching across its surface for thousands of kilometers. Under this moon’s frozen ice shell, however, scientists have detected an enormous amount of liquid water. Evidence from a past mission, Galileo, strongly suggests to us that under the 10–30-kilometer-thick crust lies an ocean more than 100 kilometers deep.
A true-size comparison between Europa (bottom left), the Moon, and Earth (Image Credit: Image Credit: NASA/JPL).
Where Does Europa Get Its Heat?
This subsurface ocean is particularly exciting because it may hold every ingredient needed to host life. No sunlight can penetrate the thick ice shell of this moon, so instead, Europa keeps its ocean hot thanks to the world it’s orbiting, Jupiter. The gas giant’s gravity causes constant flexing in Europa’s interior, which generates heat because of tidal friction. Scientists think this likely causes hydrothermal vents – something akin to underwater volcanoes, which are known to be places on Earth where life can not only exist, but thrive.
The launch of NASA’s Europa Clipper on October 14, 2024 (Image Credit: Image Credit: NASA/Kim Shiflett).
The Europa Clipper
To investigate these possibilities, NASA’s new mission, the Europa Clipper, will conduct tens of flybys of the icy moon after reaching the Jupiter system in the year 2030. Instead of orbiting just Europa, the spacecraft will orbit Jupiter itself, and repeatedly pass by the moon at different angles, allowing it to map the icy shell as well as Europa’s interior in unprecedented detail. Instruments on board the Clipper will probe the world for salts, organics, and the electrical signature of the ocean itself, all in an effort to better understand its potential habitability.
The Europa Lander, a follow-up mission to the Clipper (Artwork Credit: NASA/JPL-Caltech).
Future Missions?
The Europa Clipper will not be the only spacecraft exploring Jupiter’s moons. ESA’s Jupiter Icy Moons Explorer (JUICE) mission is also on its way to the Jovian system, and will study not only Europa, but also Ganymede and Callisto. Beyond this mission, astronomers are also working on a follow-up mission to the Clipper, known as the Europa Lander. This concept would deliver a robotic lander directly onto the surface of Europa, which would drill or scoop material from the moon to analyze it for biosignatures and direct signs of alien life.