**1. Introduction**

The Dawn Mission was the first mission exploring two different planetary objects in the asteroid belt between Mars and Jupiter, the asteroid Vesta and the dwarf planet Ceres. Asteroid Vesta is the second most massive asteroid (2.59079 x 1020 kg) with a mean diameter of 525 km and a mean density of 3.456 ± 0.035 g/ cm (e.g., [1, 2]). Vesta is believed to be a dry, differentiated proto-planet with an iron core of about 220 km in diameter, a mantle with diogenite compositions and an igneous crust [1, 3, 4]. Asteroid Vesta is a fully differentiated planetary body with a complex topography [2] and a multifaceted morphology including impact basins, various forms of impact craters, large troughs extending around the equatorial region, enigmatic dark material, mass wasting features and surface alteration processes [2, 5, 6]. Vesta's topography reveals extreme height differences resulting in steep slopes, locally exceeding 40° [2, 7, 8]. Those steep slopes result in craters with an unusual asymmetrical shape, where a sharp crater rim exists on the uphill side, and a subdued rim on the downhill side [7]. Impact craters on Vesta range from fresh to highly degraded, suggesting an intensive cratering history [2, 5] similar to the Moon. Vesta is believed to be the host body of HED meteorites (Howardite-Eucrite-Diogenite) (e.g., [9, 10]). The vestan surface is mainly composed of Howardite material with localized enrichments of Eucrite and Diogenite [11, 12]. The surface material consists of thick (100 meters to a few kilometers), multilayered sheets of regolith with different albedos, formed by the accumulation of ejecta from numerous impacts that have resurfaced Vesta over time [2, 13].

The dwarf planet Ceres is the largest object in the asteroid belt with a diameter of 940 km, a mean density of 2.162 ± 0.008 g/cm and a mass of 9.3835 x 1020 kg. Ceres is the only dwarf planet in the inner Solar System, which is supposed to be a relict ocean world [14, 15]. Recent observations by Dawn suggest that Ceres is a weakly differentiated body with a 40 km thick volatile-dominated crust and a rocky mantle down to a depth of 100 km comprising remnants of brines and hydrated rocks such as clays [16]. The crust is thought to be dominated by a mixture of ammoniated phyllosilicates, carbonates, salts, clathrate hydrates and no more than 30–40% water ice [17–20]. This volatile-rich outer layer is suggested to have an average thickness of 41.0 km [21–23]. The brines within the mantle of Ceres could be related to residual liquid from the freezing of a global ocean, as already proposed prior to the Dawn mission [24]. Several locations on Ceres's crust are enriched in salt compounds such as carbonates and ammonium chlorides [25]. A very large amount of the water could exist in the form of clathrate hydrates, which is conforming to geophysical conclusions for the abundance of water in Ceres's crust [17, 20, 26]. Since Ceres's globally homogenous surface is supposed to be made of material formed deep inside, a large-scale formation mechanism is suggested for that scenario. However, local heterogeneities associated with impact craters and landslides containing sodium carbonate and other salts suggest that those components are available in the shallow subsurface [26]. Sodium carbonates are found in brines of two remarkable emplacements on Ceres: Ahuna Mons [27, 28] and the bright (faculae) material in Occator crater (e.g., [19, 29]). Recent emplacement of bright deposits sourced from brines confirms that Ceres is a persistently geologically active world [19]. Generally, sodium carbonates are related to large impacts that can source deep material [26]. The most distinctive features found on both bodies are impact craters. Cratering processes on planetary bodies happen continuously and cause the formation of a large variety of impact crater morphologies. Images from the Dawn Spacecraft have revealed a diversity of impact craters, including craters with an individual appearance. The shape of an impact crater, and mainly its ejecta distribution, is the effect of a multifaceted interaction of topographic setting [30]. The majority of impact craters are more or less symmetrical and circular in shape. They display a classical circular bowl-shaped form with crater rims on the same elevation level at every azimuth and approximately parabolic interior profiles. Special topographic and subsurface conditions on both bodies have led to the development of special crater types. This chapter covers these special crater types found on Vesta and Ceres.
