but are not connected with, the craters Mammoth, Lascaux, and Kartchner. Some grooves are related to major impact events, for example a set opposite Vienna Regio. Craters Ida is one of the most densely cratered bodies yet explored in the Solar System, and impacts have been the primary process shaping its surface. Cratering has reached the saturation point, meaning that new impacts erase evidence of old ones, leaving the total crater count roughly the same. It is covered with craters of all sizes and stages of degradation, and ranging in age from fresh to as old as Ida itself. The oldest may have been formed during the breakup of the Koronis family parent body. The largest crater, Lascaux, is almost across. Region 2 contains nearly all of the craters larger than in diameter, but Region 1 has no large craters at all. Some craters are arranged in chains. Ida's major craters are named after caves and lava tubes on Earth. The crater Azzurra, for example, is named after a submerged cave on the island of Capri, also known as the Blue Grotto. Azzurra seems to be the most recent major impact on Ida. The ejecta from this collision is distributed discontinuously over Ida and is responsible for the large-scale color and albedo variations across its surface. An exception to the crater morphology is the fresh, asymmetric Fingal, which has a sharp boundary between the floor and wall on one side. Another significant crater is Afon, which marks Ida's prime meridian. The craters are simple in structure: bowl-shaped with no flat bottoms and no central peaks. They are distributed evenly around Ida, except for a protrusion north of crater Choukoutien which is smoother and less cratered. The ejecta excavated by impacts is deposited differently on Ida than on planets because of its rapid rotation, low gravity and irregular shape. Ejecta blankets settle asymmetrically around their craters, but fast-moving ejecta that escapes from the asteroid is permanently lost. Composition Ida was classified as an S-type asteroid based on the similarity of its reflectance spectra with similar asteroids. S-types may share their composition with stony-iron or ordinary chondrite (OC) meteorites. The composition of the interior has not been directly analyzed, but is assumed to be similar to OC material based on observed surface color changes and Ida's bulk density of 2.27–3.10 g/cm3. OC meteorites contain varying amounts of the silicates olivine and pyroxene,