Pre-Nectarian

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.

Pre-Nectarian
4533 – 3920 Ma
Chronology
Lunar geologic timescale
-4500 —
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Periods on the Lunar Geologic Timescale. Axis scale: Millions of years ago.
Usage information
Celestial bodyEarth's Moon
Time scale(s) usedLunar Geologic Timescale
Definition
Chronological unitPeriod

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[1][2] (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 Orientalis 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),[3] but these divisions are not used on any geologic maps.

Early ImbrianLate ImbrianPre-NectarianNectarianEratosthenianCopernican period
Millions of years before present

Impact Basins
Impact basins as categorized by Wilhelms et al. (1987)[4] Note: Italicized are proposed basins.
Basin Diameter (km) Age Group
Procellarum 3,200 1
South Pole-Aitken 2,500 1
Tsiolkovskiy-Stark 700 2
Grissom-White 600 2
Insularum 600 2
Marginis 580 2
Flamsteed-Billy 570 2
Balmer-Kapteyn 550 2
Werner-Airy 500 2
Pingré-Hausen 300 2
Al-Khwarizmi/King 590 2
Fecunditatis 990 3
Australe 880 3
Tranquillitatis 800 3
Mutus-Vlacq 700 3
Nubium 690 3
Lomonosov-Fleming 620 3
Ingenii 650 4
Poincaré 340 4
Keeler-Heaviside 780 4
Coulomb-Sarton 530 5
Smythii 840 5
Lorentz 360 6
Arnundsen-Ganswindt 355 7
Schiller-Zucchius 325 7
Planck 325 7
Birkhoff 330 7
Freundlich-Sharonov 600 8
Grimaldi 430 9
Apollo 505 9

Relationship to Earth's geologic time scale

Since little or no 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[5] to subdivide the unofficial terrestrial Hadean eon. In particular, it is sometimes found that the 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
  • Hadean eon-related topics

References
  1. 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.
  2. Fritz J., Bitsch B., Kührt E., Morbidelli A., Tornow C., Wünnemann K., Fernandes V.A., Grenfell L.J., Rauer H., Wagner R. and 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
  3. Don Wilhelms (1987). Geologic History of the Moon. U.S. Geological Survey Professional Paper 1348.
  4. Wilhelms, Don; McCauley, John; Trask, Newell (1987). "The Geologic History of the Moon": 148. doi:10.3133/pp1348. Cite journal requires |journal= (help)
  5. W. Harland; R. Armstrong; A. Cox; L. Craig; A. Smith; D. Smith (1990). A Geologic time scale 1989. Cambridge University Press.
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