Image source: astronomycentral.co.uk
Europa is one of Jupiter's moon slightly smaller than the Earth's Moon. It is beleaved that Europa has a iron core whit a rocky mantle and a undergraond ocean of slaty water. This ocean is deep enough to cover the whole surface and being far from the sun, the surface of it is globally frozen over. The ocean heat comes from friction forces generated by orbiting arownd massive planet Jupiter.
Europa orbits Jupiter every 3.5 days and is phase locked just like Earth's Moon so one side of it faces Jupiter all the time. The friction is generated because Europa has a eccentric orbit (an oval not a circle orbit) so when it is close to Jupiter the tide is much higher than when it is far from it. Thus tidal forces raise and lower the sea beneath the ice, causing constant motion and very likely causing the cracks seen on the Europa's surface from robotic probes.
This tidal force causes Europa to be warmer that it would otherwise according to his distance of about 780.000.000 Km (485.000.000 miles) from the Sun, more that five time further as the distance from Earth to sun. This heat could prove critical to the survival of simple organisms within the ocean, if they exist.
Discovered on 8 January 1610 by Galileo Galilei along with three other moons. Europa was the first moon discovered orbiting a planet other than Earth. This discovery eventually led to understanding that planets in our solar system orbit the Sun, instead of our solar system revolving around Earth. Galileo apparently had observed Europa on 7 January 1610. but had been unable to differentiate it from Io until next night.
Galileo originally called Europa Medicean planet, after the Medici family. This name was used for a couple of centuries until the mid-1800s wen the moons are renamed, Io, Europa, Ganymede and Callisto because it became apparent that naming moons by number would be very confusing as new additional moons were being discovered.
Europa is named after the daughter of Agenor. Europa was abducted by Zeus (Greek equivalent of the Roman god Jupiter), who had taken the shape of a spotless white bull. Europa was so delighted by the gentle beast that she decked it with flowers and rode upon its back. Zeus seizing his opportunity rode away with her into the ocean to the island of Crete, where he transformed back into his true shape. Europa bore Zeus many children, including Minos.
Mass (kg) - 4.8e+22
Mass (Earth = 1) - 8.0321e-03
Equatorial radius (km) - 1,569
Equatorial radius (Earth = 1) - 2.4600e-01
Mean density (gm/cm^3) - 3.01
Mean distance from Jupiter (km) - 670,900
Rotational period (days) - 3.551181
Orbital period (days) - 3.551181
Mean orbital velocity (km/sec) - 13.74
Orbital eccentricity - 0.009
Orbital inclination (degrees) - 0.470
Escape velocity (km/sec) - 2.02
Visual geometric albedo - 0.64
Magnitude (Vo) - 5.29