Dione is a moon of the planet Saturn. It was first photographed in some detail when the Voyager 1 mission passed by Saturn in 1980. The Cassini spacecraft started taking more closeup pictures in 2004, and we now know much more about this moon.
How big is Dione?
Dione is 1118 km across. This is much smaller than our Moon, which is almost 3,500 km across. It is one-fifth as large as Titan, the largest moon in orbit around Saturn.
What is its surface like?
This is a cold, icy world with a thin layer of oxygen for its atmosphere. The side of the moon that faces toward the direction of its orbit is covered from craters that were made by collisions with asteroids. On the back side are bright, wispy streaks across the surface. These are cliffs in the ice that were caused when the surface shifted about.
How long is a day on Dione?
It takes 2.74 days to complete an orbit around Saturn. This is just under 2 days and 18 hours. It also takes the same amount of time for the moon to rotate around the axis. This means that the same side of Dione is always facing toward Saturn, in much the same was as our Moon always keeps the same face toward us.
What is it made of?
Dione has a covering of ice surrounding a rocky interior. It has a higher portion of rock inside than any other moon of Saturn except Titan.
How much would Dione's gravity pull on me?
A person standing on the surface would weigh less than one-thirtieth as much as they would on Earth.
Who is it named after?
This moon is named for one of the titans from Greek mythology. She was an addition to the original twelve titans mentioned by the Greek poet Hesiod.
How was it discovered?
It was discovered by the Italian astronomer Giovanni Cassini in the year 1684. At the time he was the director of the Paris Observatory in France.