Eos, Transactions American Geophysical Union

Close encounter with Saturn's Moon Iapetus



Following the Cassini spacecraft's 10 September flyby of Saturn's moon Iapetus, scientists now are examining hundreds of transmitted images of the moon's reflectance, heavily cratered surface, and a 20-kilometer-high mountain ridge along the equator that gives Iapetus an irregular walnut-like shape.

Carolyn Porco, Cassini imaging team leader at the Space Science Institute, Boulder, Colo., compared the flyby to something out of the book Alice in Wonderland by Lewis Carroll. “Our flight over the surface of Iapetus was like a non-stop free fall, down the rabbit hole. Very few places in our solar system are more bizarre than the patchwork of pitch dark and snowy bright we've seen on this moon,” she said. The flyby, which brought Cassini just 1640 kilometers above Iapetus's surface—100 times closer than a 2004 encounter by the same spacecraft— will help scientists to better understand the chemical composition of the surface and look for evidence of a faint atmosphere. Iapetus images are available at: http://saturn.jpl .nasa.gov,http://www.nasa.gov/cassini, and http://ciclops.org.