Editing 4 Vesta (section)

==Geology==
{{stack|
[[File:Vestan interior PIA15510.jpg|thumb|Cut-away schematic of Vestan core, mantle, and crust]]
[[File:MillbillillieMeteorite.jpg|thumb|Eucrite meteorite]]
}}

A large collection of potential samples from Vesta is accessible to scientists, in the form of over 1200&nbsp;[[HED meteorite]]s (Vestan [[achondrite]]s), giving insight into Vesta's geologic history and structure. [[NASA Infrared Telescope Facility]] (NASA IRTF) studies of asteroid {{mpl|(237442) 1999 TA|10}} suggest that it originated from deeper within Vesta than the HED meteorites.<ref name="Vestainterior"/>

Vesta is thought to consist of a metallic iron–nickel [[planetary core|core]], variously estimated to be 90&nbsp;km<ref name=park>{{Cite journal |last=Park |first=R. S. |last2=Ermakov |first2=A. I. |last3=Konopliv |first3=A. S. |last4=Vaughan |first4=A. T. |last5=Rambaux |first5=N. |last6=Bills |first6=B. G. |last7=Castillo-Rogez |first7=J. C. |last8=Fu |first8=R. R. |last9=Jacobson |first9=S. A. |last10=Stewart |first10=S. T. |last11=Toplis |first11=M. J. |date=2025-04-23 |title=A small core in Vesta inferred from Dawn’s observations |url=https://www.nature.com/articles/s41550-025-02533-7 |journal=Nature Astronomy |language=en |pages=1–11 |doi=10.1038/s41550-025-02533-7 |issn=2397-3366|doi-access=free }}</ref> to 220&nbsp;km<ref name="Russell2012"/> in diameter, an overlying rocky [[olivine]] [[mantle (geology)|mantle]], with a surface [[crust (geology)|crust]] of similar composition to HED meteorites.

From the first appearance of [[calcium–aluminium-rich inclusion]]s (the first solid matter in the [[Solar System]], forming about 4.567&nbsp;billion years ago), a likely time line is as follows:<ref name="Ghosh1998" /><ref name="Righter1997" /><ref name="Drake2001" /><ref name="Sahijpal2007" /><ref name="Gupta2010" />

{|class=wikitable
|+Timeline of the evolution of Vesta
|-
!2–3&nbsp;million years
|Accretion completed
|-
!4–5&nbsp;million years
|Complete or almost complete melting due to [[radioactive decay]] of [[Aluminium-26|<sup>26</sup>Al]], leading to separation of the metal core
|-
!6–7&nbsp;million years
|Progressive crystallization of a [[convection|convecting]] molten [[mantle (geology)|mantle]]. Convection stopped when about 80% of the material had crystallized
|-
|colspan=2|[[Extrusive (geology)|Extrusion]] of the remaining molten material to form the [[crust (geology)|crust]], either as [[basalt]]ic [[lava]]s in progressive [[eruption]]s, or possibly forming a short-lived [[magma]] ocean.
|-
|colspan=2|The deeper layers of the crust [[crystallization|crystallize]] to form [[plutonic]] rocks, whereas older [[basalts]] are [[metamorphic rock|metamorphosed]] due to the pressure of newer surface layers.
|-
|colspan=2|Slow cooling of the interior
|}

Vesta is the only known intact asteroid that has been resurfaced in this manner. Because of this, some scientists refer to Vesta as a protoplanet.<ref name="nasa-dawn20110329"/>

{|class=wikitable
|+Composition of the Vestan crust (by depth)<ref name="Takeda1997"/>
|-
|A [[lithification|lithified]] [[regolith]], the source of [[howardite]]s and [[breccia]]ted [[eucrite]]s.
|-
|[[Basalt]]ic [[lava flow]]s, a source of non-cumulate [[eucrite]]s.
|-
|Plutonic rocks consisting of [[pyroxene]], [[pigeonite]] and [[plagioclase]], the source of cumulate [[eucrite]]s.
|-
|Plutonic rocks rich in [[orthopyroxene]] with large grain sizes, the source of [[diogenite]]s.
|}
On the basis of the sizes of [[V-type asteroid]]s (thought to be pieces of Vesta's crust ejected during large impacts), and the depth of Rheasilvia crater (see below), the crust is thought to be roughly {{convert|10|km|mi|0}} thick.<ref name="Yamaguchi1995"/>
Findings from the ''Dawn'' spacecraft have found evidence that the troughs that wrap around Vesta could be graben formed by impact-induced faulting (see Troughs section above), meaning that Vesta has more complex geology than other asteroids. The impacts that created the Rheasilvia and Veneneia craters occurred when Vesta was no longer warm and plastic enough to return to an equilibrium shape, distorting its once rounded shape and prohibiting it from being classified as a dwarf planet today.{{citation needed|date=August 2022}}

===Regolith===
Vesta's surface is covered by [[regolith]] distinct from that found on the [[Moon]] or asteroids such as [[25143 Itokawa|Itokawa]]. This is because [[space weathering]] acts differently. Vesta's surface shows no significant trace of [[nanophase iron]] because the [[Asteroid impact|impact]] speeds on Vesta are too low to make rock melting and vaporization an appreciable process. Instead, regolith evolution is dominated by [[brecciation]] and subsequent mixing of bright and dark components.<ref name="Pieters2012"/> The dark component is probably due to the infall of [[carbon]]aceous material, whereas the bright component is the original Vesta basaltic soil.<ref name="McCord2012"/>