Shop Windows to the Universe

Earth Science Rocks! Select one of our four cool NESTA t-shirts from our online store, and express your love of Earth and space science!
These are two pictures of Iapetus. Some parts of the moon's surface are bright white. Other areas are very dark. The Cassini spacecraft took these pictures.
Click on image for full size
Images courtesy of NASA/JPL/Space Science Institute.

Iapetus

Iapetus was discovered by G. Cassini in 1672. Iapetus is the 2nd farthest moon from Saturn, with a standoff distance of 3,561,300 km. Iapetus is one of the icy moons, similar to the Galilean satellites. Iapetus is about as wide as California is long, 1440 km, or 960 miles, which makes it about the same size as Rhea, a moderately large icy moon.

Iapetus is very much like Rhea, Enceladus, Dione, and Tethys except that it looks completely different. In fact, Iapetus is unique, and does not look like any other object in the solar system in that its surface appears to be half dark and half bright.

Last modified October 8, 2009 by Randy Russell.

Shop Windows to the Universe Science Store!

Our online store includes books on science education, ranging from evolution, classroom research, and the need for science and math literacy!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Galilean Satellites

The Galilean satellites are the 4 major moons of Jupiter, Io, Europa, Ganymede, and Callisto. In this picture, Io, and Ios surface, are shown on the left-most end, then Europa, and its surface, then Ganymede,...more

The Phoebe Ring Around Saturn

The Phoebe Ring is one of the rings around the planet Saturn. The Phoebe Ring is much bigger than Saturn's other rings. It is about 100 times larger than the main ring system. Saturn's moon Phoebe orbits...more

Saturn's Rings

Many people like Saturn's rings. Although Saturn isn't the only planet with rings, it is the only planet famous for them. Almost every image or drawing of the planet has the rings included. But few people...more

Prometheus

Prometheus is a small moon of Saturn. It was discovered by S. Collins and others in 1980 from photos taken by the Voyager 1 spacecraft. This moon's name comes from Greek mythology. Prometheus was a Titan...more

Medium-sized Moons of Saturn

Saturn has // Call the moon count function defined in the document head print_moon_count('saturn'); moons. Many of those are tiny chunks of rock or ice only a few kilometers (miles) across. One of Saturn's...more

Large and Medium-sized Moons of Saturn

Saturn has // Call the moon count function defined in the document head print_moon_count('saturn'); moons. Many of those are tiny chunks of rock or ice only a few kilometers (miles) across. One of Saturn's...more

How Titan Formed

Titan is similar to the other icy moons, but Titan is the only icy moon to have a big atmosphere. It is natural to ask how is this possible? The nebula was colder near Saturn, than near Jupiter. The nebula...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA