Scientists have suggested that the mountain range did not come from forces within Iapetus--they rather fell from the sky. In a new study, published online in arXiv (but yet to be peer-reviewed), researchers created 3D images of the peaks, working with Cassini data. They found that most of the triangular-shaped peaks were near their "angle of repose," the fixed angle a material reaches as it erodes and falls toward the ground. This idea is suggestive of an "exogenic" origin (meaning, from outside the moon). "The evidence of slope angles close to the angle of repose make the case for an exogenic origin more plausible," they wrote. Presumably the peaks would have a different shape, or a wider variety of shapes, if they were created by forces within Iapetus.