Editing Planetary differentiation (section)

==Heating==
When the [[Sun]] ignited in the [[solar nebula]], [[hydrogen]], [[helium]] and other volatile materials were evaporated in the region around it. The [[solar wind]] and [[radiation pressure]] forced these low-density materials away from the Sun. Rocks, and the elements comprising them, were stripped of their early atmospheres,<ref>{{Cite journal|last=Ahrens|first=T J|date=1993|title=Impact Erosion of Terrestrial Planetary Atmospheres|url=http://dx.doi.org/10.1146/annurev.ea.21.050193.002521|journal=Annual Review of Earth and Planetary Sciences|volume=21|issue=1|pages=525–555|doi=10.1146/annurev.ea.21.050193.002521|bibcode=1993AREPS..21..525A |hdl=2060/19920021677 |issn=0084-6597|hdl-access=free}}</ref> but themselves remained, to accumulate into [[protoplanet]]s.

Protoplanets had higher concentrations of [[radioactive]] elements early in their history, the quantity of which has reduced over time due to [[radioactive decay]]. For example, the [[Hafnium–tungsten dating|hafnium-tungsten]] system demonstrates the decay of two unstable isotopes and possibly forms a timeline for accretion. Heating due to radioactivity, impacts, and gravitational pressure melted parts of protoplanets as they grew toward being [[planet]]s. In melted zones, it was possible for denser materials to sink towards the center, while lighter materials rose to the surface. The compositions of some [[meteorite]]s ([[achondrite]]s) show that differentiation also took place in some [[asteroid]]s (e.g. [[4 Vesta|Vesta]]), that are parental bodies for meteoroids. The short-lived radioactive isotope [[aluminium-26|<sup>26</sup>Al]] was probably the main source of heat.<ref name=":0" /> 

When protoplanets [[Accretion (astrophysics)|accrete]] more material, the energy of impact causes local heating. In addition to this temporary heating, the gravitational force in a sufficiently large body creates pressures and temperatures which are sufficient to melt some of the materials. This allows [[chemical reaction]]s and [[density]] differences to mix and separate materials,<ref name=":1">{{Citation|last1=Sohl|first1=Frank|title=Differentiation, Planetary|date=2014|url=http://link.springer.com/10.1007/978-3-642-27833-4_430-2|encyclopedia=Encyclopedia of Astrobiology|pages=1–5|editor-last=Amils|editor-first=Ricardo|place=Berlin, Heidelberg|publisher=Springer Berlin Heidelberg|language=en|doi=10.1007/978-3-642-27833-4_430-2|isbn=978-3-642-27833-4|access-date=2021-11-08|last2=Breuer|first2=Doris|editor2-last=Gargaud|editor2-first=Muriel|editor3-last=Cernicharo Quintanilla|editor3-first=José|editor4-last=Cleaves|editor4-first=Henderson James|url-access=subscription}}</ref> and soft materials to spread out over the surface. Another external heat source is [[tidal heating]]. 

On [[Earth]], a large piece of molten [[iron]] is sufficiently denser than [[continental crust]] material to force its way down through the crust to the [[mantle (geology)|mantle]].<ref name=":0" /> 

In the outer Solar System, a similar process may take place but with lighter materials: they may be [[hydrocarbons]] such as [[methane]], [[water]] as liquid or ice, or frozen [[carbon dioxide]].<ref>{{Cite journal|last1=Prialnik|first1=Dina|last2=Merk|first2=Rainer|date=2008|title=Growth and evolution of small porous icy bodies with an adaptive-grid thermal evolution code: I. Application to Kuiper belt objects and Enceladus|url=https://www.sciencedirect.com/science/article/pii/S0019103508001462|journal=Icarus|language=en|volume=197|issue=1|pages=211–220|doi=10.1016/j.icarus.2008.03.024|bibcode=2008Icar..197..211P |issn=0019-1035|url-access=subscription}}</ref>

===Fractional melting and crystallization===
[[Magma]] in the Earth is produced by [[partial melting]] of a source rock, ultimately in the [[Mantle (geology)|mantle]]. The melt extracts a large portion of the "incompatible elements" from its source that are not stable in the major minerals. When magma rises above a certain depth the dissolved minerals start to crystallize at particular pressures and temperatures. The resulting solids remove various elements from the melt, and melt is thus depleted of those elements. Study of trace elements in [[igneous rock]]s thus gives us information about what source melted by how much to produce a magma, and which minerals have been lost from the melt.

===Thermal diffusion===
When material is unevenly heated, lighter material migrates toward hotter zones and heavier material migrates towards colder areas, which is known as [[thermophoresis]], thermomigration, or the [[Thermophoresis|Soret effect]]. This process can affect differentiation in [[magma chamber]]s. A deeper understanding of this process can be drawn back to a study done on the Hawaiian lava lakes. The drilling of these lakes led to the discovery of crystals formed within magma fronts. The magma containing concentrations of these large crystals or [[Phenocryst|phenocrysts]] demonstrated differentiation through the chemical melt of crystals.