The Copernican Period in the

lunar geologic timescale The lunar geological timescale (or selenological timescale) divides the history of Earth's Moon into five generally recognized periods: the Copernican, Eratosthenian, Imbrian (Late and Early epochs), Nectarian, and Pre-Nectarian. The boundaries o ...

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 Ejecta (from the Latin: "things thrown out", singular ejectum) are particles ejected from an area. In volcanology, in particular, the term refers to particles including pyroclastic materials ( tephra) that came out of a volcanic explosion and magm ...

, but a small area of mare

basalt Basalt (; ) is an 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 surface of a rocky planet or moon. More than 90% of a ...

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.

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.

Examples

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

Tycho Tycho is a masculine given name, a latinization of Greek Τύχων, from the name of Tyche ( grc-gre, Τύχη, link=no), the Greek goddess of fortune or luck. The Russian form of the name is '' Tikhon'' (Тихон). People Given name * Tych ...

, Aristillus,

Autolycus In Greek mythology, Autolycus (; Ancient Greek: Αὐτόλυκος ''Autolykos'' 'the wolf itself') was a successful robber who had even the power of metamorphosing both the stolen goods and himself. He had his residence on Mount Parnassus and ...

, 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 of ...

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, Harpalus,

Carpenter Carpentry is a skilled trade and a craft in which the primary work performed is the cutting, shaping and installation of building materials during the construction of buildings, ships, timber bridges, concrete formwork, etc. Carpenters tra ...

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 Anaxagoras (; grc-gre, Ἀναξαγόρας, ''Anaxagóras'', "lord of the assembly"; 500 – 428 BC) was a Pre-Socratic Greek philosopher. Born in Clazomenae at a time when Asia Minor was under the control of the Persian Empire, ...

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

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 ...

, Necho,

Giordano Bruno Giordano Bruno (; ; la, Iordanus Brunus Nolanus; born Filippo Bruno, January or February 1548 – 17 February 1600) was an Italian philosopher, mathematician, poet, cosmological theorist, and Hermetic occultist. He is known for his cosmolo ...

O'Day O'Day is a surname of Irish origin. Notable people with the surname include: *Alan O'Day (1940–2013), American singer-songwriter *Anita O'Day (1919–2006), American jazz singer *Aubrey O'Day (born 1984), American singer, dancer, actress, songwr ...

, Crookes, Robertson, Vavilov, 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 Apollo 14 (January 31, 1971February 9, 1971) was the eighth crewed mission in the United States Apollo program, the third to land on the Moon, and the first to land in the lunar highlands. It was the last of the " H missions", landings at s ...

) Image:Crookes crater as08-13-2318hr.jpg, Interior of Crookes (

Apollo 8 Apollo 8 (December 21–27, 1968) was the first crewed spacecraft to leave low Earth orbit and the first human spaceflight to reach the Moon. The crew orbited the Moon ten times without landing, and then departed safely back to Earth. The ...

) 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, 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