Land of the Day, Land of the Night

Although it is no longer "Uncharted Land", the origin of the dark territory of Cassini Regio on Iapetus remains a mystery.
Also puzzling is the equatorial ridge that bisects this terrain, and how it fits into the story of the moon's strange brightness dichotomy. The ridge is seen here, curving along the lower left edge of Iapetus.

The view looks down onto the Northern Hemisphere of Iapetus, and shows terrain on the moon's Leading Hemisphere.

The image was taken in polarized green light with the Cassini spacecraft narrow-angle camera on Nov. 12, 2005 at a distance of approx. 417.000 Km (such as about 259.000 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 95°. Image scale is about 2 Km (about 1 mile) per pixel.