Editing Pre-Nectarian

{{short description|Geologic period, 4533 to 3920 million years ago}}{{Infobox geologic timespan
| name                         = Pre-Nectarian
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| top_bar                      = Lunar
| time_start                   = 4533
| time_end                     = 3920
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| timeline                     = Lunar periods
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| celestial_body               = moon
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| timescales_used              = Lunar Geologic Timescale
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| chrono_unit                  = Period
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The '''pre-Nectarian period''' of the [[lunar geologic timescale]] runs from 4.533 billion years ago (the time of the initial formation of the [[Moon]]) to 3.920 billion years ago, when the [[Nectaris Basin]] was formed by a large impact. It is followed by the [[Nectarian]] period.

==Description==
Pre-Nectarian rocks are rare in the lunar sample suite; they are mostly composed of lunar highlands material which have been heavily churned, brecciated, and thermally affected by subsequent impacts, particularly during the Heavy Bombardment Eon<ref>Fernandes V. A., Fritz J., Weiss B., Garrick-Bethel and Shuster D. (2013) The bombardment history of the Moon as recorded by 40Ar-39Ar chronology. Meteor. and Planet. Sci. 48, 241–269. DOI: 10.1111/maps.12054.</ref><ref>Fritz J., Bitsch B., Kührt E., Morbidelli A., Tornow C., Wünnemann K., Fernandes V.A., Grenfell L.J., Rauer H., Wagner R. and [[Stephanie C. Werner|Werner S.C.]] (2014) Earth-like habitats in planetary systems. Planetary and Space Science 98, 254–267. https://dx.doi.org/ 10.1016/j.pss.2014.03.003i</ref> (HBE; a period of 0.6-1 Gy from the formation of the Moon until at least the formation of the Imbrium Basin ~3.9 Ga, or even later with the formation of Orientale Basin) that marks the approximate beginning of the [[Nectarian]] period.  The primary pre-Nectarian lunar highland material is dominated by the rock type [[anorthosite]], which suggests that the early stage of lunar crustal formation occurred via mineral crystallization of a global [[magma]] ocean.

This geologic period has been informally subdivided into the ''Cryptic Era'' (4.533 - 4.172 Ga ago) and Basin Groups 1-9 (4.172 - 3.92 Ga ago),<ref name="W87">{{cite book | title =Geologic History of the Moon  | url =http://ser.sese.asu.edu/GHM/ | last = Don Wilhelms | publisher =  U.S. Geological Survey Professional Paper 1348 | year = 1987}}</ref> but these divisions are not used on any geologic maps. Similarly the later period has also been called the ''Aitkenian'' period.

{{Timeline_Lunar_Geological_Timescale}}

== Impact basins ==
{|
|+ '''Lunar impact basins'''<br/>as categorized by Wilhelms ''et al''. (1987)<ref>
{{cite book
 |last1=Wilhelms |first1=Don
 |last2=McCauley |first2=John
 |last3=Trask    |first3=Newell
 |year=1987
 |title=The geologic history of the Moon
 |series=Professional Paper
 |page=148
 |publisher=[[US Geological Survey]]
 |doi=10.3133/pp1348 |doi-access=free
 |url=http://pubs.er.usgs.gov/publication/pp1348
}}
</ref>
|- style="text-align:center;vertical-align:top;"
|rowspan="3"|
{| class="wikitable sortable" style="vertical-align:center;text-align:left;"
|- style="text-align:center;background:#EAECF0;border:1px solid black;"
|rowspan="2" style="vertical-align:center;"| '''Basin name'''
|style="vertical-align:bottom;"| '''Diameter'''
|style="vertical-align:bottom;"| '''Age-<br/>group'''
|- style="vertical-align:center;text-align:center;background:#EAECF0;"
| (km)
| (nr.)
|-
| [[Oceanus Procellarum|''Procellarum'']]
|align="right"| 3,200
|rowspan="2" align="center"| 1
|-
| [[South Pole–Aitken basin|South Pole-Aitken]]
|align="right"| 2,500
<!-- | 1 -->
|-
| ''[[Tsiolkovskiy (crater)|Tsiolkovskiy]]-[[Stark (crater)|Stark]]''
|align="right"| 700
|rowspan="9" align="center"| 2
|-
| ''[[Grissom (crater)|Grissom]]-[[White (crater)|White]]''
|align="right"| 600
<!-- | 2 -->
|-
| [[Mare Insularum|''Insularum'']]
|align="right"| 600
<!-- | 2 -->
|-
| [[Mare Marginis|''Marginis'']]
|align="right"| 580
<!-- | 2 -->
|-
| ''[[Flamsteed (crater)|Flamsteed]]-[[Billy (crater)|Billy]]''
|align="right"| 570
<!-- | 2 -->
|-
| ''[[Balmer (crater)|Balmer]]-[[Kapteyn (crater)|Kapteyn]]''
|align="right"| 550
<!-- | 2 -->
|-
| ''[[Werner (crater)|Werner]]-[[Airy (lunar crater)|Airy]]''
|align="right"| 500
<!-- | 2 -->
|-
| ''[[Pingré (crater)|Pingré]]-[[Hausen (crater)|Hausen]]''
|align="right"| 300
<!-- | 2 -->
|-
| ''[[Al-Khwarizmi (crater)|Al-Khwarizmi]] / [[King (crater)|King]]''
|align="right"| 590
<!-- | 2 -->
|-
| [[Mare Fecunditatis|Fecunditatis]]
|align="right"| 990
|rowspan="6" align="center"| 3
|-
| [[Mare Australe|Australe]]
|align="right"| 880
<!-- | 3 -->
|-
| [[Mare Tranquillitatis|Tranquillitatis]]
|align="right"| 800
<!-- | 3 -->
|-
| ''[[Mutus (crater)|Mutus]]-[[Vlacq (crater)|Vlacq]]''
|align="right"| 700
<!-- | 3 -->
|-
| [[Mare Nubium|Nubium]]
|align="right"| 690
<!-- | 3 -->
|-
| [[Lomonosov (lunar crater)|Lomonosov]]-[[Fleming (crater)|Fleming]]
|align="right"| 620
<!-- | 3 -->
|- style="text-align:center;vertical-align:top;"
|}
|
{| class="wikitable sortable" style="vertical-align:center;text-align:left;"
|- style="text-align:center;background:#EAECF0;border:1px solid black;"
|rowspan="2" style="vertical-align:center;"| '''Basin name'''
|style="vertical-align:bottom;"| '''Diameter'''
|style="vertical-align:bottom;"| '''Age-<br/>group'''
|- style="vertical-align:center;text-align:center;background:#EAECF0;"
| (km)
| (nr.)
|-
| [[Mare Ingenii|Ingenii]]
|align="right"| 650
|rowspan="3" align="center"| 4
|-
| [[Poincaré (crater)|Poincaré]]
|align="right"| 340
<!-- | 4  -->
|-
| [[Keeler (lunar crater)|Keeler]]-[[Heaviside (lunar crater)|Heaviside]]
|align="right"| 780
<!-- | 4  -->
|-
| [[Coulomb-Sarton Basin|Coulomb-Sarton]]
|align="right"| 530
|rowspan="2" align="center"| 5
|-
| [[Mare Smythii|Smythii]]
|align="right"| 840
<!-- | 5  -->
|-
| [[Lorentz (crater)|Lorentz]]
|align="right"| 360
|align="center"| 6
|-
| ''[[Amundsen (crater)|Amundsen]]-[[Ganswindt (crater)|Ganswindt]]''
|align="right"| 355
|rowspan="4" align="center"| 7
|-
| [[Schiller-Zucchius Basin|Schiller-Zucchius]]
|align="right"| 325
<!-- | 7  -->
|-
| [[Planck (crater)|Planck]]
|align="right"| 325
<!-- | 7  -->
|-
| [[Birkhoff (crater)|Birkhoff]]
|align="right"| 330
<!-- | 7  -->
|-
| [[Freundlich-Sharonov Basin|Freundlich-Sharonov]]
|align="right"| 600
|align="center"| 8
|-
| [[Grimaldi (crater)|Grimaldi]]
|align="right"| 430
|rowspan="2" align="center"| 9
|-
| [[Apollo (crater)|Apollo]]
|align="right"| 505
<!-- | 9  -->
|}
|-
|style="text-align:left;vertical-align:top;padding-left: 2em;"| {{small|For basins with no article, the two prominent <br/>craters' names are separately linked to their <br/>respective articles.}}
|-
|style="text-align:left;vertical-align:bottom;padding-left: 2em;"| {{small|Names of proposed basins are ''italicized''.<br/>&nbsp;}}
|}

==Relationship to Earth's geologic time scale==
Since little or no [[geology|geological]] evidence on [[Earth]] exists from the time spanned by the pre-Nectarian period of the Moon, the pre-Nectarian has been used as a guide by at least one notable scientific work<ref>{{cite book | title = A Geologic time scale 1989 | publisher = Cambridge University Press | year = 1990 |author1=W. Harland |author2=R. Armstrong |author3=A. Cox |author4=L. Craig |author5=A. Smith |author6=D. Smith }}</ref> to subdivide the unofficial terrestrial [[Hadean]] [[eon (geology)|eon]]. In particular, the [[Hadean|Hadean eon]] is subdivided into the [[Cryptic era]], [[Basin Groups]] 1-9, [[Nectarian]] and [[Lower Imbrian]], though the first two of these lunar divisions are informal and collectively make up the pre-Nectarian.

==See also==
*{{C|Hadean|Hadean eon–related topics}}

==References==
{{reflist}}

==External links==
*[http://www.palaeos.org/Hadean Palaeos.org: Hadean eon] {{Webarchive|url=https://web.archive.org/web/20160728124239/http://www.palaeos.org/Hadean |date=2016-07-28 }}

[[Category:Pre-Nectarian| ]]
[[Category:Hadean]]