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 system A ray system comprises radial streaks of fine '' ejecta'' thrown out during the formation of an impact crater, looking somewhat like many thin spokes coming from the hub of a wheel. The rays may extend for lengths up to several times the diameter ...

s. 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 Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

has covered part of (and is thus younger than) some of the rays of the Copernican crater

Lichtenberg Lichtenberg () is the eleventh borough of Berlin, Germany. In Berlin's 2001 administrative reform it absorbed the former borough of Hohenschönhausen. Overview The district contains the Tierpark Berlin in Friedrichsfelde, the larger of Berlin ...

, and therefore the basalt is mapped as Copernican age.

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 Space weathering is the type of weathering that occurs to any object exposed to the harsh environment of outer space. Bodies without atmospheres (including the Moon, Mercury, the asteroids, comets, and most of the moons of other planets) take on ...

processes. Operationally, this period was originally defined as the time at which impact craters "lost" their bright

s. 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 Anorthosite () is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic minera ...

materials) is deposited on the low albedo mare, it will remain bright even after being space weathered.

Examples

Other than Copernicus itself, there are many examples of Copernican craters. Large examples on the near side include Tycho, Aristillus, Autolycus, Stevinus,

Kepler Johannes Kepler (; ; 27 December 1571 – 15 November 1630) was a German astronomer, mathematician, astrologer, natural philosopher and writer on music. He is a key figure in the 17th-century Scientific Revolution, best known for his laws o ...

Theophilus Theophilus is a male given name with a range of alternative spellings. Its origin is the Greek word Θεόφιλος from θεός (God) and φιλία (love or affection) can be translated as "Love of God" or "Friend of God", i.e., it is a theoph ...

, Taruntius, Eudoxus, Bürg,

Römer The Römer (German surname, "Roman") is a medieval building in the Altstadt of Frankfurt am Main, Germany, and one of the city's most important landmarks. The Römer is located opposite the Old St. Nicholas church and has been the city hall ('' ...

Harpalus Harpalus (Greek: Ἅρπαλος) son of Machatas was an aristocrat of Macedon and boyhood friend of Alexander the Great in the 4th century BC. Harpalus was repeatedly entrusted with official roles by Alexander and absconded three times with la ...

, Carpenter,

Philolaus Philolaus (; grc, Φιλόλαος, ''Philólaos''; ) was a Greek Pythagorean and pre-Socratic philosopher. He was born in a Greek colony in Italy and migrated to Greece. Philolaus has been called one of three most prominent figures in the Pyt ...

, Anaxagoras, Glushko, Hayn, Zucchius, and Rutherfurd. Examples on the far side include

Ohm Ohm (symbol Ω) is a unit of electrical resistance named after Georg Ohm. Ohm or OHM may also refer to: People * Georg Ohm (1789–1854), German physicist and namesake of the term ''ohm'' * Germán Ohm (born 1936), Mexican boxer * Jörg Ohm (b ...

Jackson Jackson may refer to: People and fictional characters * Jackson (name), including a list of people and fictional characters with the surname or given name Places Australia * Jackson, Queensland, a town in the Maranoa Region * Jackson North, Qu ...

King King is the title given to a male monarch in a variety of contexts. The female equivalent is queen, which title is also given to the consort of a king. *In the context of prehistory, antiquity and contemporary indigenous peoples, the tit ...

, Necho, Giordano Bruno, O'Day,

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Robertson Robertson may refer to: People * Robertson (surname) (includes a list of people with this name) * Robertson (given name) * Clan Robertson, a Scottish clan * Robertson, stage name of Belgian magician Étienne-Gaspard Robert (1763–1837) Places ...

Vavilov Vavilov (russian: Вави́лов) is a Russian surname. Notable people with the surname include: * Andrey Petrovich Vavilov (b. 1961), Russian politician and businessman * Nikolai Vavilov (1887–1943), Russian geneticist * Sergey Ivanovich Vavi ...

, and Sharonov.Unified Geologic Map of the Moon
C. M. Fortezzo, P. D. Spudis, S. L. Harrel, 2020. United States Geological Survey. File:Copernicus (LRO) 2.png, Copernicus File:Tycho LRO.png, Tycho File:Hayn crater LROC WAC.jpg, Hayn File:Jackson LRO WAC.jpg, Jackson File:Necho crater AS14-70-9671.jpg, Necho ( Apollo 14) Image:Crookes crater as08-13-2318hr.jpg, Interior of Crookes ( Apollo 8) Many craters visited by the

Apollo Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label=Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label= ...

astronauts were of Copernican age. These include North Ray and South Ray on

Apollo 16 Apollo 16 (April 1627, 1972) was the tenth crewed mission in the United States Apollo space program, administered by NASA, and the fifth and penultimate to land on the Moon. It was the second of Apollo's " J missions", with an extended sta ...

, 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 The Neoproterozoic Era is the unit of geologic time from 1 billion to 538.8 million years ago. It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods. It is ...

era of the

Proterozoic The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided ...

eon and the whole of the

Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 538.8 million years to the present, and it began with the Cambrian Period, when anima ...

eon. So, while animal life bloomed on Earth, the Moon's geologic activity was coming to an end.

References

* Lunar geologic periods {{Moon-stub