Europa is the icy moon of Jupiter with a global ocean of salty liquid water beneath its cracked crust, one of the most promising places to search for life.
At a glance
| radius | 1,560 km (0.245 × Earth) |
|---|---|
| distance from its planet | 671,000 km |
| one orbit | 3.55 days |
| reflects | 67% of the sunlight it gets |
Read off the piece’s own catalogue, the same values it draws with.
About Europa
Europa is slightly smaller than our Moon, a rocky body with a shell of water ice. The surface is bright, smooth and young, with few impact craters, and is crossed everywhere by long reddish cracks and ridges, along with patches of jumbled terrain where blocks of ice seem to have broken apart and refrozen.
The ocean underneath was inferred from magnetic measurements by the Galileo spacecraft: Europa disturbed Jupiter’s field the way an electrically conducting layer of salty water would. Tidal flexing, from the same orbital rhythm that heats Io, keeps that ocean from freezing. With liquid water, rock beneath it and a source of energy, Europa has many of the ingredients life is thought to need.
That makes it a prime target for exploration. NASA’s Europa Clipper is on its way to study the moon in a long series of close flybys, measuring the ice shell, the ocean and the surface chemistry.
What you see in the piece
Europa is one of the brightest moons, its clean ice reflecting most of the sunlight that reaches it. You can see it close to Jupiter, between Io and Ganymede; from another star it cannot be seen.
Measured or modelled
The ocean is inferred, not seen; how thick the ice shell is, and whether water from below ever reaches the surface, are still open questions.
Questions
Does Europa have an ocean?
Almost certainly. Magnetic measurements by the Galileo spacecraft revealed an electrically conducting layer beneath the ice, best explained by a global ocean of salty liquid water.
Could there be life on Europa?
Nobody knows. Its ocean has liquid water, contact with rock and a supply of energy from tides, which makes it one of the best places in the Solar System to look, but no sign of life has been found.