Editing 243 Ida (section)

=== Craters ===
Ida is one of the most densely cratered bodies yet explored in the Solar System,<ref name="ChapmanBeltonVeverkaNeukum1994p237" /><ref name="Chapman1994p363" /> and impacts have been the primary process shaping its surface.<ref>{{harvnb|Geissler|Petit|Greenberg|1996|pp=57–58}}</ref> Cratering has reached the saturation point, meaning that new impacts erase evidence of old ones, leaving the total crater count roughly the same.<ref name="Chapman1996p707p708">{{harvnb|Chapman|1996|pp=707–708}}</ref> It is covered with craters of all sizes and stages of degradation,<ref name="Chapman1994p363" /> and ranging in age from fresh to as old as Ida itself.<ref name="Chapman1996p707" /> The oldest may have been formed during the breakup of the [[Koronis family]] parent body.<ref name="Chapman1995p496" /> The largest crater, Lascaux, is almost {{convert|12|km|mi|abbr=on}} across.<ref name="BottkeCellinoPaolicchiBinzel2002p10" /><ref name="USGS">{{harvnb|USGS}}</ref> Region 2 contains nearly all of the craters larger than {{convert|6|km|mi|abbr=on}} in diameter, but Region 1 has no large craters at all.<ref name="Chapman1996p707" /> Some craters are arranged in chains.<ref name="GreeleySullivanPappalardoVeverka1994p469" />
[[File:Fingal on 243 Ida.svg|left|thumb|360x360px|Asymmetric {{convert|1.5|km|mi|abbr=on}} wide crater Fingal at 13.2°S, 39.9°E<ref name="USGS" />]]
Ida's major craters are named after caves and [[lava tube]]s on Earth. The crater Azzurra, for example, is named after a submerged cave on the island of [[Capri]], also known as the ''[[Blue Grotto (Capri)|Blue Grotto]]''.<ref name="GreeleyBatson2001p393">{{harvnb|Greeley|Batson|2001|p=393}}</ref> Azzurra seems to be the most recent major impact on Ida.<ref name="GeisslerPetitDurdaGreenberg1996p141">{{harvnb|Geissler|Petit|Durda|Greenberg|1996|p=141}}</ref> The ejecta from this collision is distributed discontinuously over Ida<ref name="Chapman1996p710" /> and is responsible for the large-scale color and [[albedo]] variations across its surface.<ref>{{harvnb|Bottke|Cellino|Paolicchi|Binzel|2002|p=9}}</ref> An exception to the crater morphology is the fresh, asymmetric Fingal, which has a sharp boundary between the floor and wall on one side.<ref name="pappalardo124" /> Another significant crater is Afon, which marks Ida's [[prime meridian]].<ref name="Archinal2018"/>

The craters are simple in structure: bowl-shaped with no flat bottoms and no central peaks.<ref name="pappalardo124">{{harvnb|Sullivan|Greeley|Pappalardo|Asphaug|1996|p=124}}</ref> They are distributed evenly around Ida, except for a protrusion north of crater Choukoutien which is smoother and less cratered.<ref>{{harvnb|Sullivan|Greeley|Pappalardo|Asphaug|1996|p=128}}</ref> The [[ejecta]] excavated by impacts is deposited differently on Ida than on planets because of its rapid rotation, low gravity and irregular shape.<ref name="GeisslerPetitGreenberg1996p58" /> [[Ejecta blanket]]s settle asymmetrically around their craters, but fast-moving ejecta that escapes from the asteroid is permanently lost.<ref>{{harvnb|Geissler|Petit|Durda|Greenberg|1996|p=155}}</ref>