Equatorial ridges are a feature of at least three of Saturn's moons: the large moon Iapetus and the tiny moons Atlas and Pan. They are ridges that follow closely the moon's equator. They appear to be unique to the Saturnian system, but it is uncertain whether the occurrences are related or a coincidence. All three were discovered by the Cassini probe in 2005.
The ridge on Iapetus is nearly 20 km wide, 13 km high and 1,300 km long. The ridge on Atlas is proportionally even more remarkable given the moon's much smaller size, and distorts the moon's shape into an odd, UFO-like appearance. Images of Pan are less clear, but show a structure similar to that of Atlas.
It is not certain how these ridges formed, or whether there is any connection between them. Because Atlas and Pan orbit within the rings of Saturn, a likely explanation for their ridges is that they sweep up ring particles as they orbit, which build up around their equators. This theory is less applicable to Iapetus, which orbits far beyond the rings. One scientist has suggested that Iapetus swept up a ring before being somehow expelled to its current, distant orbit. Others think it was stationary and it is the rings that have been pulled away from it, falling into Saturn's gravity field. But most scientists prefer to assume that Iapetus's ridge was produced by some kind of internal source and is unrelated to the ridges on Atlas and Pan.
... A further mystery of Iapetus is the equatorial ridge that runs along the center of Cassini Regio, about 1,300 km long, 20 km wide, 13 km high ... Peaks in the ridge rise more than 20 km above the surrounding plains, making them some of the tallest mountains in the Solar System ... The ridge forms a complex system including isolated peaks, segments of more than 200 km and sections with three near parallel ridges ...
Famous quotes containing the word ridge:
“All sound heard at the greatest possible distance produces one and the same effect, a vibration of the universal lyre, just as the intervening atmosphere makes a distant ridge of earth interesting to our eyes by the azure tint it imparts to it.”
—Henry David Thoreau (18171862)