Europa
What is Europa?
Moons· Diameter 3,122 km. A moon of Jupiter thought to hide more water beneath its ice than all of Earth's oceans. It is a leading place to look for life, and Europa Clipper, launched in 2024, arrives in 2030 to study it closely.
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Orbit and size
| Diameter | 3,122 km |
|---|---|
| Parent | Jupiter |
| Note | buried ocean, 2× Earth's seas |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Parent planet and sibling moons
Related events
Why Europa Clipper passes 49 times instead of orbiting
When Europa Clipper reaches Jupiter in 2030, it will not go into orbit around Europa. Instead it will loop widely around Jupiter and sweep past Europa 49 times. The reason is radiation. Jupiter's strong magnetic field traps fast-moving particles, and Europa orbits right where they are concentrated. A spacecraft that stayed there would have its electronics fail within months. By spending only a few hours close in on each pass and then pulling back, Clipper can last for a four-year mission.
At its closest, Clipper dips to 25 km above the surface, and each pass follows a different track so that together they cover the whole moon. An ice-penetrating radar will measure how thick the shell is, and if plumes exist, instruments will sample their molecules directly. Its solar panels span 30 m, the largest on any NASA planetary spacecraft, and its electronics sit inside a thick metal vault to survive the radiation.
Clipper launched on 14 October 2024, gained speed flying past Mars in March 2025, and will swing past Earth in December 2026 before reaching Jupiter in April 2030. The first clue to Europa's ocean came from the Galileo spacecraft, which orbited Jupiter from 1995. It measured the magnetic field that Jupiter creates inside Europa, and the readings could be explained only by a layer of electrically conducting salt water beneath the ice.
The moon in depth
Europa looks like a white ball of ice, but scientists think an ocean lies hidden beneath its thick shell. That ocean may hold about twice as much water as all of Earth's oceans combined. The reddish-brown streaks across the surface are cracks in the ice, and they are read as places where water or soft ice from below rose through the gaps.
The ocean stays liquid in this cold place thanks to Jupiter. Europa circles Jupiter every 3.55 days, keeping in step with its neighbours Io and Ganymede: while Io goes around four times, Europa goes around twice and Ganymede once. These regular tugs keep Europa's orbit slightly stretched. So each time it swings closer to Jupiter and away again, Europa is squeezed and stretched like dough, and that flexing produces heat inside.
Life as we know it needs liquid water, a source of energy and the right chemical ingredients. Europa may well have all three, which makes it one of the leading places to search for life beyond Earth. The Hubble Space Telescope has several times caught what may be plumes of water vapour rising from the surface, but they have not been confirmed. From 2030 Europa Clipper will make 49 close passes to measure the ice and study what the ocean is made of.
Frequently asked
- How big is Europa?
- The diameter of Europa is 3,122 km.
- What is notable about Europa?
- The note of Europa is buried ocean, 2× Earth's seas.
- Which planet does Europa orbit?
- Europa orbits Jupiter.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.