Editing Mercury (planet) (section)

==== Plains ====
There are two geologically distinct plains regions on Mercury.<ref name="Spudis01" /><ref name="WagWolIva01" /> Gently rolling, hilly [[Inter-crater plains on Mercury|plains in the regions between craters]] are Mercury's oldest visible surfaces,<ref name="Spudis01" /> predating the heavily cratered terrain. These inter-crater plains appear to have obliterated many earlier craters, and show a general paucity of smaller craters below about {{convert|30|km|mi|abbr=on}} in diameter.<ref name="WagWolIva01" />

Smooth plains are widespread flat areas that fill depressions of various sizes and bear a strong resemblance to lunar maria. Unlike lunar maria, the smooth plains of Mercury have the same albedo as the older inter-crater plains. Despite a lack of unequivocally volcanic characteristics, the localization and rounded, lobate shape of these plains strongly support volcanic origins.<ref name="Spudis01" /> All the smooth plains of Mercury formed significantly later than the Caloris basin, as evidenced by appreciably smaller crater densities than on the Caloris ejecta blanket.<ref name="Spudis01" />