Black and white GIF of Europa in front of Jupiter.

Europa transit movie, animated GIF. Hubble time-lapse sequence of images showing Europa crossing in front of Jupiter while Jupiter moves and rotates behind Europa. This image is taken in near ultraviolet light. Credits: NASA, ESA, W. Sparks (STScI)

10 Need-to-Know Things

10. Familiar Size

Europa is slightly smaller than Earth’s Moon and barely one-quarter the diameter of Earth itself.


9. A Darker Realm

Europa orbits Jupiter, the fifth planet from the Sun, and so is about 484 million miles (778 million kilometers) from the Sun.


8. Locked On

Every 3.5 Earth days Europa rotates once on its axis and completes one orbit of Jupiter, so the same side of Europa always faces Jupiter.


7. Icy Moon

Europa's surface is mostly solid water ice. It is crisscrossed by fractures.


6. Bring Your Spacesuit

Europa has an extremely thin oxygen atmosphere — far too thin for humans to breathe.


5. Nothing in its Orbit

Europa has no moons of its own.


4. Ringless

Europa has no rings, but some moons in the solar system may have had rings in the past.


3. We've visited before

Europa has been visited by several spacecraft. Galileo made repeated visits to Europa while in Jupiter orbit. Europa Clipper is next on deck.


2. All These Worlds

Abundant liquid water, energy and chemistry make Europa one of the best places in the solar system to seek present day life beyond Earth.


1. Bring a Towel

Europa's subsurface ocean might contain more than twice as much water as Earth.

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