The Jovians

Another universal characteristic of Jovians is that they all have rings. While we've known for centuries that Saturn has rings, it is only recently that we've been able to detect and image the rings of the other Jovians.

Because the Jovians have no hard surface, storms occurring in their atmospheres can go on for centuries. The best example of this is the Great Red Spot of Jupiter, a Jovian hurricane that has been going on for at least 400 years.

All of the Jovians have moons in abundance. Jupiter is noted for its four major moons, the Galilean satellites. Saturn is noted for its large but opaquely covered moon Titan, which we "visited" recently.

All of the Jovians have significant magnetic fields, fields greater than the Earth's magnetic field, so like Earth, they experience aurorae at their north and south poles.

You can't land a space ship on a Jovian planet: it's just a gas ball made up of hydrogen and helium. As you descend into a Jovian atmosphere, the density of the atmosphere does increase (due to gravitational pressure), so deep in the interior of a Jovian, the gaseous atmosphere starts to liquify.

All the Jovians are huge, by comparison to the Terrestrials: Jupiter's diameter is more than eleven times greater than Earth's diameter. Huge doesn't mean dense though: the densities of the Jovians are comparable to that of water. The densities of the Terrestrials, by comparison, are similar to relatively heavy metals. Curiously, the density of Saturn is less than that of water, so the joke goes that Saturn would float in a bathtub, if one could be found that large.