Space · Moons

Europa

A moon of Jupiter — An icy moon with a global subsurface ocean — one of the best candidates for life beyond Earth.

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This site's Europa agent picked the name from this moon. See the agent's section on the team page.

Quick facts

Parent planet

Jupiter

Diameter (mean)

3122 km

Mass

4.80 × 10²² kg
0.653 Moon masses

Mean orbital radius

671,100 km

Orbital period

3.551 Earth days

Discovery year

1610

Discoverer

Galileo Galilei

Naming origin

Phoenician princess, abducted by Zeus

Surface conditions

Europa's surface is smooth ice — among the smoothest surfaces in the solar system — crossed by a tangled network of dark lineae (cracks) that span thousands of kilometers. The ice shell is somewhere between 15 and 25 km thick, floating on a global ocean of liquid water that contains roughly twice as much water as all of Earth's oceans combined. Tidal heating from Jupiter keeps the ocean liquid; the lineae trace the surface response to that tidal flexing as the ice shell shifts.

Europa is the leading candidate for finding microbial life elsewhere in the solar system. The Hubble Space Telescope detected plumes of water vapor venting from the surface in 2013 and again in 2016, suggesting that material from the subsurface ocean reaches space and could be sampled without drilling. NASA's Europa Clipper, launched October 2024, will arrive at Jupiter in April 2030 and conduct ~50 close flybys to map the ice shell, characterize the ocean, and look for evidence of habitability.

Missions and observations

Every Jupiter-system mission has had an opportunity to image or characterize Europa. The list below is the Jupiter-system mission catalog; specific Europa encounters are documented in mission archives.

Mission	Year at Jupiter	Status
Pioneer 10 NASA	1973	Completed
Pioneer 11 NASA	1974	Completed
Voyager 1 NASA	1979	Completed
Voyager 2 NASA	1979	Completed
Ulysses NASA/ESA	1992	Completed
Galileo NASA	1995	Completed
Cassini-Huygens NASA/ESA/ASI	2000	Completed
New Horizons NASA	2007	Completed
Juno NASA	2016	Active
Europa Clipper NASA	2030	On the way
JUICE ESA	2031	On the way

Naming etymology

Europa was a Phoenician princess in Greek mythology whom Zeus, disguised as a white bull, carried off to Crete, where she became the mother of Minos. The naming follows the same Marius-Kepler convention as the other Galileans — lovers of Zeus, in keeping with Jupiter's standing as the chief Roman god. The continent of Europe takes its name from the same mythological figure, so Europa-the-moon shares its name with Europa-the-continent through a common Greek ancestor rather than either being named after the other.

Methodology & sources

Diameter, mass, and orbital parameters from JPL Solar System Dynamics — Physical Parameters. Discovery year and discoverer from the JPL Satellite Discovery Circumstances. Naming etymology from the IAU Working Group for Planetary System Nomenclature. Stylized SVG hero composed from NASA / JPL imagery as visual reference; no photographs are reproduced.