Copernican period

Copernican
Copernican
1100 – 0 Ma PreN I N E C
Chronology
−4500 — – −4000 — – −3500 — – −3000 — – −2500 — – −2000 — – −1500 — – −1000 — – −500 — – 0 —	Pre-Nectarian Nectarian Imbrian Eratosthenian Copernican Late Early
	Periods on the Lunar Geologic Timescale. Axis scale: Millions of years ago.;
Usage information
Celestial body	Earth's Moon
Time scale(s) used	Lunar Geologic Timescale
Definition
Chronological unit	Period

The Copernican Period in the lunar geologic timescale runs from approximately 1.1 billion years ago to the present day. The base of the Copernican period is defined by impact craters that possess bright optically immature ray systems. The crater Copernicus is a prominent example of rayed crater, but it does not mark the base of the Copernican period.

Copernican age deposits are mostly represented by crater ejecta, but a small area of mare basalt has covered part of (and is thus younger than) some of the rays of the Copernican crater Lichtenberg, and therefore the basalt is mapped as Copernican age.^[1]

Definition

The base of the Copernican period is defined based on the recognition that freshly excavated materials on the lunar surface are generally "bright" and that they become darker over time as a result of space weathering processes. Operationally, this period was originally defined as the time at which impact craters "lost" their bright ray systems. This definition, however, has recently been subjected to some criticism as some crater rays are bright for compositional reasons that are unrelated to the amount of space weathering they have incurred. In particular, if the ejecta from a crater formed in the highlands (which is composed of bright anorthositic materials) is deposited on the low albedo mare, it will remain bright even after being space weathered.

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 id:prenectarian   value:rgb(0.823,0.302,0.380)
 id:nectarian value:rgb(0.898,0.329,0.071)
 id:imbrian   value:rgb(0,0.481,0.811)
 id:earlyimbrian      value:rgb(0,0.404,0.741) 
 id:lateimbrian    value:rgb(0,0.557,0.882) 
 id:eratosthenian   value:rgb(0.238,0.839,0.728) 
 id:copernican     value:rgb(0.5,0.5,0.5)

Period = from:-4533 till:0 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:500 start:-4500 ScaleMinor = unit:year increment:100 start:-4500

PlotData=

 align:center textcolor:black fontsize:8 mark:(line,black) width:25 shift:(0,-5)

 bar:Period

 from: -1100   till:    0   text:Copernican  color:copernican   
 from:-3200   till: -1100   text:Eratosthenian  color:eratosthenian   
 from:-3850   till: -3200  text:Imbrian      color:imbrian  
 from: -3920  till: -3850  text:N shift:(2,-5)       color:nectarian
 from: start  till: -3920  text:Pre-Nectarian       color:prenectarian

 bar:Epoch

 from: -3200  till: 0       color:white
 from:  -3800 till: -3200   text:Late  color:lateimbrian
 from: -3850  till: -3800   text:Early shift:(-20,-5)  color:earlyimbrian             
 from: start  till: -3850   color:white

</timeline>

Millions of years before present

Examples

Other than Copernicus itself, there are many examples of Copernican craters. Large examples on the near side include Tycho, Aristillus, Autolycus, Stevinus, Kepler, Theophilus, Taruntius, Eudoxus, Bürg, Römer, Harpalus, Carpenter, Philolaus, Anaxagoras, Glushko, Hayn, Zucchius, and Rutherfurd. Examples on the far side include Ohm, Jackson, King, Necho, Giordano Bruno, O'Day, Crookes, Robertson, Vavilov, and Sharonov.^[2]

500 m diameter crater with rays in Mare Serenitatis
Copernicus
Tycho
Hayn
Jackson
Necho (Apollo 14)
Interior of Crookes (Apollo 8)

Many craters visited by the Apollo astronauts were of Copernican age. These include North Ray and South Ray, visited by Apollo 16, which were dated by cosmic ray exposure to approximately 50 million and 2 million years age, respectively.

Relationship to Earth's geologic time scale

Its Earth equivalents are the Neoproterozoic era of the Proterozoic eon and the whole of the Phanerozoic eon. So, while animal life bloomed on Earth, the Moon's geologic activity was coming to an end.

References

^ Wilhelms, Don E.; McCauley, John F.; Trask, Newell J. (1987). "The geologic history of the Moon". USGS. Professional paper 1348.
^ Unified Geologic Map of the Moon, C. M. Fortezzo, P. D. Spudis, S. L. Harrel, 2020. United States Geological Survey.

Martel, Linda M. V. (2004-09-28). "Lunar Crater Rays Point to a New Lunar Time Scale". Hawai'i Institute of Geophysics and Planetology (HIGP). Planetary Science Research Discoveries (PSRD).

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[1] Wilhelms, Don E.; McCauley, John F.; Trask, Newell J. (1987). "The geologic history of the Moon". USGS. Professional paper 1348.

[2] Unified Geologic Map of the Moon, C. M. Fortezzo, P. D. Spudis, S. L. Harrel, 2020. United States Geological Survey.

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