50 Fun Facts About Europa (Moon)

What is Europa's surface mostly made of?

Gerard Kuiper's ground-based observations confirmed the water-ice composition in 1957.

What is thought to lie beneath Europa's icy crust?

Tidal flexing keeps it liquid, and it may hold two or three times the water of Earth's oceans.

Who discovered Europa in January 1610?

He first saw Io and Europa as a single blur on 7 January and separated them the next night.

Among Jupiter's four Galilean moons, Europa is which?

It is also the least massive, yet still a planetary-mass moon visible with binoculars.

Europa is slightly smaller than which body?

At just over 3,100 km across it is the sixth-largest moon in the Solar System.

Like all the Galilean satellites, Europa is named after what kind of figure?

Europa was the Phoenician daughter of the king of Tyre and became queen of Crete.

Lacking mountains and craters, Europa is the what known solid object in the Solar System?

Its surface is young because it is so tectonically active.

What keeps Europa's subsurface ocean liquid?

Jupiter's pull stretches and relaxes the moon as its slightly eccentric orbit brings it nearer and farther.

Europa's very thin atmosphere is composed mainly of which gas?

It is produced non-biologically when radiation splits surface water ice.

In which year was Europa discovered?

Galileo used a 20× refracting telescope at the University of Padua.

Which Saturnian moon is the only other one known to show water-vapour plumes?

Europa's plumes, if real, erupt at about 7000 kg/s against Enceladus's 200 kg/s.

Which rocket launched NASA's Europa Clipper in October 2024?

It is the largest interplanetary spacecraft NASA has ever launched.

Who launched the Jupiter Icy Moons Explorer (Juice) in April 2023?

It will make two Europa flybys but is mainly a Ganymede mission.

The Galileo probe orbited Jupiter from 1995 until which year?

It was deliberately destroyed in Jupiter's atmosphere to avoid contaminating the moons.

In myth, Europa was courted by Zeus and became queen of where?

She was the mother of King Minos.

How long does Europa take to orbit Jupiter?

Its orbit is nearly circular, with an eccentricity of only 0.009.

What is Europa's approximate diameter?

That makes it the fifteenth-largest object in the Solar System.

How does the volume of Europa's ocean compare with Earth's oceans?

Estimates put the ocean around 100 km deep under 10–30 km of ice.

What are the dark streaks crisscrossing Europa's surface called?

The larger bands are more than 20 km wide with a lighter central stripe.

Spectra suggest Europa's reddish streaks may be rich in which salt?

Sulfur compounds are suspected of supplying the reddish colour itself.

Which observatory imaged a possible 200 km-high plume near Europa's south pole in 2012?

More than 20 times the height of Everest, if the interpretation holds.

Which probes made the first flybys of Europa, in 1973 and 1974?

Their photos were low-resolution compared with later missions.

In which year did the two Voyager probes pass through the Jovian system?

Their images first hinted at a liquid ocean under the ice.

Which orbiter made a close flyby of Europa in September 2022?

New Horizons had imaged Europa in 2007 on its way to Pluto.

Under Galileo's numbering scheme, Europa is Jupiter's satellite number what?

Later discoveries of inner moons mean it is now physically the sixth satellite out.

At its 2024 launch, Europa Clipper was scheduled to enter Jupiter orbit in which year?

Flybys of Europa were planned to begin in March 2031 after gravity assists from Mars and Earth.

The 2024 NASA Europa mission's name references what?

The fast merchant ships plied trade routes; the probe will pass Europa as often as every two weeks.

Europa's surface gravity is roughly what fraction of Earth's?

Too weak to hold an atmosphere thick enough for wind, clouds or a sky colour.

Which Space Shuttle carried the Galileo probe into Earth orbit in 1989?

Galileo then used Venus and Earth flybys to reach Jupiter in December 1995.

What icy spikes, up to 15 m tall, may cover Europa's equator?

Overhead sunlight sublimates the ice into vertical blades; they would complicate any landing.

Who may have discovered Europa independently of Galileo and later named it?

His mythological names fell out of use until the mid-20th century.

Europa ranks where among the Solar System's largest moons?

It is the least massive of the four Galilean satellites.

How thick is Europa's outer layer of water, ice and ocean combined, estimated to be?

Part is frozen crust, part a liquid ocean beneath.

Under the "thick ice" model, how thick is Europa's solid ice crust?

The rival thin-ice model puts it at only a few kilometres.

What are the circular and elliptical "freckle" features on Europa called?

Many are domes, some pits and some smooth dark spots.

Which named region is the textbook example of Europa's jumbled, iceberg-like terrain?

Chaos areas look like icebergs frozen into a jumbled sea.

How old is Europa's surface estimated to be?

The estimate comes from how often comets should have struck it.

What daily radiation dose would a human receive on Europa's surface?

That is enough to cause severe illness or death in a single Earth day.

Which US Poet Laureate wrote the poem engraved on Europa Clipper?

Public names were etched on a microchip attached to the tantalum plate.

Which astronomer's 1957 ground observations revealed Europa's water-ice composition?

Gravitational calculations had already suggested a water-rich body.

What does the JPL prototype BRUIE stand for?

It is an autonomous underwater vehicle meant to search Europa's ocean for life.

Europa's tidal forces are about how many times stronger than the Moon's effect on Earth?

The kneading is what keeps the ocean from freezing solid.

What is Europa's approximate orbital radius around Jupiter?

The other figures are the Moon's, Ganymede's and Io's distances.

What is the albedo of Europa's icy crust?

It is one of the highest of any moon, a sign of a young, active surface.

How close did Galileo come to Europa on its 1997 flyby that may have crossed a plume?

A 2018 reanalysis suggested it flew straight through erupting water vapour.

Who led the 1995 team that first detected Europa's atmosphere?

They used the Goddard High Resolution Spectrograph; Kliore's team later found an ionised layer.

What is the estimated eruption rate of Europa's plumes?

If confirmed, a flyby could sample the ocean without drilling through kilometres of ice.

What is the orbital eccentricity of Europa's nearly circular orbit?

Even that slight eccentricity, pumped by resonance with Io, drives the tidal heating.

One full slip of Europa's ice shell relative to its interior takes at least how long?

The limit comes from comparing Voyager and Galileo photographs.

Marius attributed the idea of naming the moons after Zeus's lovers to whom?

He ranked Europa second and gave Ganymede its name "on account of its majesty of light".