APOD 3.2

Here we have not a new, super-impressive, ground-shattering shot of some space phenomena hundreds of light years away, but rather a simple picture of one of Jupiter's moons. Or rather, half of one. Europa is one of Jupiter's four primary, or otherwise known as Galilean, Moons. The other 3 are Io, Ganymede, and Callisto. It is approximately the size of our own moon, and is the 15th largest body in the Solar System.

Half of a fracture-marked Europa.

Now, it would seem that Europa's surface is similar to that of our moon's: dry, dusty, and definitely no water what-so-ever. However, that is wrong. Europa's entire surface is composed of ice! Beneath this ice, there is a subterranean sea between the ice layer and the core. Now, what would one make of the cracks on the surface? Those cracks (more properly sized as gorges) are the result of gravitational stresses on the moon by the other moons and Jupiter itself. The bodies pull on the moon in different directions, so it is only natural that it begins to fracture due to the stress. Luckily, the moons have different orbital periods, or Europa would be ripped apart entirely! Another question: How did all the lines get all skewed like that, surely the other moons don't have orbits that swing them around like that? The answer goes back to the ice layer and the subterranean sea. Scientists believe there isn't an anchor between the ice layer and the rocky core, which means that the ice has the ability to swing freely. Neat, isn't it? Below is a picture of Europa in it's entirety.