http://www.digitaljournal.com/science/mountains-on-saturn-moon-are-celestial-debris/article/383472

Mountains on Saturn moon are 'celestial debris'

Posted May 11, 2014 by Tim Sandle
Mountains at the equator on Iapetus, a moon of the planet Saturn, may have come from space rather than being formed on the surface of the satellite.
Artist s rendition of the Cassini spacecraft at Saturn.
Artist's rendition of the Cassini spacecraft at Saturn.
NASA, JPL-Caltex
A mysterious mountain ridge ringing the equator of Saturn’s moon Iapetus, which has intrigued astronomers for a decade, may in fact be a load of space rubble. Lapetus is the third-largest natural satellite of Saturn, eleventh-largest in the Solar System.
The Cassini spacecraft spied the jagged belt wrapped around Iapetus’ middle in 2004. Cassini–Huygens is a flagship-class NASA-ESA-ASI robotic spacecraft. It has studied the planet and its many natural satellites since arriving there in 2004, also observing Jupiter, the heliosphere, and testing the theory of relativity.
Since the detection of the geological ridge, scientists have debated the ridge’s origin. Some astronomers think that the volcanoes shoved up the craggy structure from beneath the moon’s surface or that tectonic activity created the range. Others think that the towering mountains, which may reach more than twice the height of Mount Everest, could be remnants of rings that once orbited the moon.
The ring theory is now more in favor following analysis of Cassini images by Erika Lopez Garcia of Brown University in Providence, R.I., and colleagues. Lapetus’ ridges have steep slopes, a clue that the mountains may have formed as cosmic debris rained down on the moon and piled high on the surface.
The scientists surmise in a research note: "Saturn's moon Iapetus has an equatorial ridge system, which may be as high as 20 km, that may have formed by endogenic forces, such as tectonic and convective forces, or exogenic processes such as debris infall. We use high-resolution topographic data to conduct a topographic analysis of the ridge, which suggests a predominantly triangular morphology, with some ridge face slopes reaching 40 degrees, allowing for an exogenic formation mechanism."