Two regions of smooth plains were observed by "Voyager 2". They generally have low relief and have far fewer craters than in the cratered terrains, indicating a relatively young surface age. In one of the smooth plain regions, Sarandib Planitia, no impact craters were visible down to the limit of resolution. Another region of smooth plains to the southwest of Sarandib is criss-crossed by several troughs and scarps. "Cassini" has since viewed these smooth plains regions, like Sarandib Planitia and Diyar Planitia at much higher resolution. "Cassini" images show these regions filled with low-relief ridges and fractures, probably caused by shear deformation. The high-resolution images of Sarandib Planitia revealed a number of small impact craters, which allow for an estimate of the surface age, either 170 million years or 3.7 billion years, depending on assumed impactor population.