Known Space -- Sol -- Jupiter -- | Europa |
Europa is the sixth of Jupiter's known satellites and the fourth largest; it is the second of the Galilean moons. Europa is slightly smaller than the Earth's Moon.
Europa and Io are somewhat similar in bulk composition to the terrestrial planets: primarily composed of silicate rock. However, Europa's density (2.97 g/cm3, a little less than the Moon's and substantially less than Earth's) indicates the lack of a dense iron core.
But Europa's surface is not at all like anything in the inner solar system. It is exceedingly smooth: few features more than a few hundred meters high have been seen. The prominent markings seem to be only albedo features or very low relief.
Europa's most striking aspect is a series of dark streaks crisscrossing the entire globe. The larger ones are roughly 20 km across with diffuse outer edges and a central band of lighter material. The current theory of their origin is that they are produced by a series of volcanic eruptions or geysers (though none have ever been observed).
Europa has a young, active surface layer of ice. Only three craters larger than 5 km in diameter have been found. Beneath Europa's surface ice there is a layer of liquid water, as much as 50 km deep in places, kept liquid by tidally generated heat.
Europa has a very tenuous atmosphere composed of oxygen. Of all the moons in the solar system only four others (Io, Ganymede, Titan and Triton) are known to have atmospheres. Unlike the oxygen in Earth's atmosphere, Europa's is not of biological origin. It is generated by sunlight and charged particles hitting Europa's icy surface producing water vapor which is subsequently split into hydrogen and oxygen. The hydrogen escapes leaving the oxygen.
Orbital Distance: 670,900 km (average) Eccentricity: 0.009 Local Year: 3.551 days (3d 13h 13m 42s) Orbital Velocity: 13.74 km/s Inclination: 0.470° Local Day: 3.551 days (3d 13h 13m 42s) Axial Tilt: n/a Diameter: 3,138 km Composition: Basaltic rock Density: 2.99 g/cm3 Mass: 4.80 x 1019 tonnes (0.008 earths) Gravity: 0.133 G Escape Velocity: 2.023 km/s Area: 30.8 million km2 Surface Material: H2O ice Atmosphere: O2 Pressure: 9.869 x 10-12 atm Albedo: 0.64 Temperature: ???°C |