Editing 243 Ida (section)

=== Regolith ===
The surface of Ida is covered in a blanket of pulverized rock, called ''[[regolith]]'', about {{convert|50|-|100|m|ft|abbr=on}} thick.<ref name="Chapman1996p707" /> This material is produced in [[impact event]]s and redistributed across Ida's surface by geological processes.<ref name="LeeVeverkaThomasHelfenstein1996p96">{{harvnb|Lee|Veverka|Thomas|Helfenstein|1996|p=96}}</ref> ''Galileo'' observed evidence of recent [[Mass wasting|downslope regolith movement]].<ref name="GreeleySullivanPappalardoVeverka1994p470">{{harvnb|Greeley|Sullivan|Pappalardo|Veverka|1994|p=470}}</ref>

Ida's regolith is composed of the [[silicate]] minerals [[olivine]] and [[pyroxene]].<ref name="Holm1994">{{harvnb|Holm|1994}}</ref><ref name="Chapman1996p701">{{harvnb|Chapman|1996|p=701}}</ref> Its appearance changes over time through a process called [[space weathering]].<ref name="Chapman1995p496" /> Because of this process, older regolith appears more red in color compared to freshly exposed material.<ref name="Chapman1996p710" />

[[File:Ejecta block on 243 Ida.svg|thumb|''Galileo'' image of a {{convert|150|m|ft|abbr=on}} block at 24.8°S, 2.8°E<ref name="LeeVeverkaThomasHelfenstein1996p90">{{harvnb|Lee|Veverka|Thomas|Helfenstein|1996|p=90}}</ref>|216x216px]]
About 20 large (40–150&nbsp;m across) ejecta blocks have been identified, embedded in Ida's regolith.<ref name="Chapman1996p707" /><ref name="GeisslerPetitDurdaGreenberg1996p141" /> Ejecta blocks constitute the largest pieces of the regolith.<ref name="SullivanGreeleyPappalardoAsphaug1996p132">{{harvnb|Sullivan|Greeley|Pappalardo|Asphaug|1996|p=132}}</ref> Because ejecta blocks are expected to break down quickly by impact events, those present on the surface must have been either formed recently or uncovered by an impact event.<ref name="Cowen1995" /><ref name="LeeVeverkaThomasHelfenstein1996p97">{{harvnb|Lee|Veverka|Thomas|Helfenstein|1996|p=97}}</ref> Most of them are located within the craters Lascaux and Mammoth, but they may not have been produced there.<ref name="LeeVeverkaThomasHelfenstein1996p97" /> This area attracts debris due to Ida's irregular gravitational field.<ref name="Cowen1995" /> Some blocks may have been ejected from the young crater Azzurra on the opposite side of the asteroid.<ref name="Stooke1997p1385" />