Evidence of tectonics on Enceladus is also derived from grooved terrain, consisting of lanes of curvilinear grooves and ridges. These bands, first discovered by "Voyager 2", often separate smooth plains from cratered regions. Grooved terrains such as the Samarkand Sulci are reminiscent of grooved terrain on Ganymede. However, unlike those seen on Ganymede, grooved topography on Enceladus is generally more complex. Rather than parallel sets of grooves, these lanes often appear as bands of crudely aligned, chevron-shaped features. In other areas, these bands bow upwards with fractures and ridges running the length of the feature. "Cassini" observations of the Samarkand Sulci have revealed dark spots (125 and 750 m wide) located parallel to the narrow fractures. Currently, these spots are interpreted as collapse pits within these ridged plain belts.