Editing 243 Ida (section)

=== Structures ===
Several major structures mark Ida's surface. The asteroid appears to be split into two halves, here referred to as ''region 1'' and ''region 2'', connected by a "waist".<ref name="Chapman1996p707" /> This feature may have been filled in by debris, or blasted out of the asteroid by impacts.<ref name="Chapman1996p707" /><ref name="Stooke1997p1385">{{harvnb|Stooke|1997|p=1385}}</ref>

Region 1 of Ida contains two major structures. One is a prominent {{convert|40|km|mi|abbr=on}} ridge named ''Townsend Dorsum'' that stretches 150 degrees around Ida's surface.<ref name="SárneczkyKereszturi2002">{{harvnb|Sárneczky|Kereszturi|2002}}</ref> The other structure is a large indentation named ''Vienna Regio''.<ref name="Chapman1996p707" />

Ida's region 2 features several sets of grooves, most of which are {{convert|100|m|ft|abbr=on}} wide or less and up to {{convert|4|km|mi|abbr=on}} long.<ref name="Chapman1996p707" /><ref name="SullivanGreeleyPappalardoAsphaug1996p131">{{harvnb|Sullivan|Greeley|Pappalardo|Asphaug|1996|p=131}}</ref> They are located near, but are not connected with, the craters Mammoth, Lascaux, and Kartchner.<ref name="SullivanGreeleyPappalardoAsphaug1996p132" /> Some grooves are related to major impact events, for example a set opposite Vienna Regio.<ref name="ThomasProckter2004">{{harvnb|Thomas|Prockter|2004}}</ref>