Europa
A moon of Jupiter
Slightly smaller than our Moon, Europa is wrapped in ice: the brightest surface of Jupiter's large moons, crossed by long reddish cracks and patches of crust broken up and frozen again. Under that shell lies an ocean of salt water, probably holding twice the water of all Earth's oceans, which makes it one of the likeliest places in the Solar System to look for life.
It goes round Jupiter in three and a half days, always with the same face towards it, so that from that side the giant hangs still in the sky, some 12 degrees wide, waxing and waning. The map comes from the Galileo probe, which flew close past it eleven times between 1996 and 2000; NASA's Europa Clipper, launched in October 2024, is due to reach Jupiter in April 2030.
Key figures
- Diameter
- 3,122 km, 0.245 × Earth
- Mass
- 1/124 of Earth's
- Surface gravity
- 1.31 m/s², 13% of Earth's
- Distance from Jupiter
- 671,100 km
- One orbit of Jupiter
- 3.55 days
- Rotation
- 3.55 days, the same face always towards Jupiter
- Temperature at the equator
- below -160 °C
- Ocean under the ice
- 60 to 150 km deep, under 15 to 25 km of ice
- Discovered
- 1610, by Galileo Galilei