Saturn's Moons

Quick Fact - Saturn has 31 known moons.

On March 24, 1655, only Earth and Jupiter were known to have moons. The next day, Christiaan Huygens added Saturn to the list when he discovered its largest moon, Titan.

Since then, we've discovered 31 natural satellites orbiting Saturn. Some, like Pan, Atlas, Prometheus, and Pandora, are "shepherd moons" that herd Saturn's orbiting particles into distinct ring. Some moons produce twisting and wave patterns in the rings.

Saturn's largest moon, Titan.

One moon, Enceladus, is one of the shiniest objects in the solar system. It's about as wide as Arizona and covered with water ice that reflects sunlight like freshly fallen snow. That makes it extremely cold, only about -201C (-330F). It may be that volcanoes on this moon erupted the icy particles that form Saturn's E-ring, and that they continuously snow back down onto its surface.

Mimas, only 392 km (244 miles) in diameter, has a giant crater one-third as wide as the moon, itself. And in its center is a peak about two-thirds the height of Mt. Everest, the highest point on Earth.

Iapetus is among the strangest of Saturn's moons. Half of it is ten times brighter than the other half.

Epimetheus and Janus trade orbits with each other every few years, taking turns being closer to their planet.

Phoebe may be a captured Centaur, an object that wandered sunward from its home in the Kuiper Belt, far beyond Pluto.

But it is mysterious Titan that intrigues scientists most.

Titan is the second-largest moon in the entire solar system (Jupiter's Ganymede is slightly larger). It's bigger than two planets, Mercury and Pluto. Circling Saturn far from the Sun, its surface temperature is only -180? C (-292? F). And it's the only moon with a dense atmosphere -- so dense, in fact, that Titan's near-surface atmospheric pressure is about 60% greater than Earth's. That's about what a scuba diver feels under 20 feet of water.

Scientists think Titan's atmosphere may resemble that of Earth when life began to form here. So studying Titan might help us learn about the early days of our own planet.

We haven't had a good look at Titan's surface yet (its thick, deep-red haze hid it from the two Voyager spacecraft that visited in 1980 and 1981), but scientists recently used the world's most powerful radar system to bounce microwaves off the giant moon - a billion kilometers away. The returning signals suggested that as much as 75% of Titan may be covered by lakes or oceans of liquid ethane and methane.

Europe's Huygens probe, named for the Dutch astronomer, is currently riding NASA's Cassini spacecraft to Saturn. Huygens is scheduled to plunge through Titan's hazy atmosphere and land on its surface in January, 2005. Unless, of course, it splashes down in a petroleum-like ocean.

When Cassini arrives at Saturn for its four-year orbital mission, we're likely to learn much more about these moons and possibly discover even more.

Moon List

Source: NASA