Mare Orientale

During the 1960s, rectified images of Mare Orientale by [[Gerard Kuiper]] at the [[Lunar and Planetary Laboratory]] gave rise to the notion of it being an [[impact crater]].{{sfn|Beals|Tanner|1975|pp=299–306}}{{sfn|Hartmann|Kuiper|1962|pp=51–66}} The structure, with the flat plain of the mare in the center, is about {{convert|900|km|mi}} across and was formed by the impact of an asteroid-sized object,{{cite web |url=http://www.lpi.usra.edu/lunar/missions/orbiter/lunar_orbiter/impact_basin/ |title=Lunar Orbiter: Impact Basin Geology |publisher=Lunar and Planetary Institute |first=Walter S. |last=Kiefer |access-date=29 October 2013}}{{cite web |url=http://stardate.org/radio/program/2008-06-17 |title=Mare Orientale |work=StarDate.org |publisher=McDonald Observatory |first=Damond |last=Benningfield |date=17 June 2008 |access-date=29 October 2013 |archive-date=26 January 2021 |archive-url=https://web.archive.org/web/20210126024328/https://stardate.org/radio/program/2008-06-17 |url-status=dead }} possibly {{convert|64|km|mi|abbr=on}} in diameter and travelling at {{convert|15|km/s|mi/s|abbr=on}}.{{cite news |url=https://theconversation.com/study-sheds-light-on-violent-asteroid-crash-that-caused-mysterious-crater-rings-on-the-moon-68093 |title=Study sheds light on violent asteroid crash that caused mysterious 'crater rings' on the moon |work=The Conversation |first=Susanne |last=Schwenzer |date=3 November 2016 |access-date=3 November 2016}}{{cite journal |title=Formation of the Orientale lunar multiring basin |journal=[[Science (journal)|Science]] |first1=Brandon C. |last1=Johnson |first2=David M. |last2=Blair |first3=Gareth S. |last3=Collins |first4=H. Jay |last4=Melosh |first5=Andrew M. |last5=Freed |display-authors=etal |volume=354 |issue=6311 |pages=441–444 |date=28 October 2016 |doi=10.1126/science.aag0518 |pmid=27789836|bibcode=2016Sci...354..441J |hdl=10044/1/42189 |doi-access=free |hdl-access=free }} Compared with most other lunar basins, Mare Orientale is less flooded by mare [[basalt]]s, so that much of the basin structure is visible. The basalt in the central portion of the Orientale basin is probably less than {{convert|1|km|mi|abbr=on}} in thickness which is much less than mare basins on the Earth-facing side of the Moon. The collision caused ripples in the lunar crust, resulting in the three concentric circular features. The innermost rings of this vast, [[multi-ringed crater]] are the inner and outer [[Montes Rook]], and the outermost ring are the [[Montes Cordillera]], {{convert|930|km|mi|abbr=on}} in diameter. Outward from here, ejecta extend some {{convert|500|km|mi|abbr=on}} from the foot of the mountains and form a rough surface with hummocks and with features radially aligned towards the center.

During the 1960s, rectified images of Mare Orientale by [[Gerard Kuiper]] at the [[Lunar and Planetary Laboratory]] gave rise to the notion of it being an [[impact crater]].{{sfn|Beals|Tanner|1975|pp=299–306}}{{sfn|Hartmann|Kuiper|1962|pp=51–66}} The structure, with the flat plain of the mare in the center, is about {{convert|900|km|mi}} across and was formed by the impact of an asteroid-sized object,{{cite web |url=http://www.lpi.usra.edu/lunar/missions/orbiter/lunar_orbiter/impact_basin/ |title=Lunar Orbiter: Impact Basin Geology |publisher=Lunar and Planetary Institute |first=Walter S. |last=Kiefer |access-date=29 October 2013}}{{cite web |url=http://stardate.org/radio/program/2008-06-17 |title=Mare Orientale |work=StarDate.org |publisher=McDonald Observatory |first=Damond |last=Benningfield |date=17 June 2008 |access-date=29 October 2013 |archive-date=26 January 2021 |archive-url=https://web.archive.org/web/20210126024328/https://stardate.org/radio/program/2008-06-17 |url-status=dead }} possibly {{convert|64|km|mi|abbr=on}} in diameter and travelling at {{convert|15|km/s|mi/s|abbr=on}}.{{cite news |url=https://theconversation.com/study-sheds-light-on-violent-asteroid-crash-that-caused-mysterious-crater-rings-on-the-moon-68093 |title=Study sheds light on violent asteroid crash that caused mysterious 'crater rings' on the moon |work=The Conversation |first=Susanne |last=Schwenzer |date=3 November 2016 |access-date=3 November 2016}}{{cite journal |title=Formation of the Orientale lunar multiring basin |journal=[[Science (journal)|Science]] |first1=Brandon C. |last1=Johnson |first2=David M. |last2=Blair |first3=Gareth S. |last3=Collins |first4=H. Jay |last4=Melosh |first5=Andrew M. |last5=Freed |display-authors=etal |volume=354 |issue=6311 |pages=441–444 |date=28 October 2016 |doi=10.1126/science.aag0518 |pmid=27789836|bibcode=2016Sci...354..441J |hdl=10044/1/42189 |doi-access=free |hdl-access=free }} Compared with most other lunar basins, Mare Orientale is less flooded by mare [[basalt]]s, so that much of the basin structure is visible. The basalt in the central portion of the Orientale basin is probably less than {{convert|1|km|mi|abbr=on}} in thickness which is much less than mare basins on the Earth-facing side of the Moon. The collision caused ripples in the lunar crust, resulting in the three concentric circular features. The innermost rings of this vast, [[multi-ringed crater]] are the inner and outer [[Montes Rook]], and the outermost ring are the [[Montes Cordillera]], {{convert|930|km|mi|abbr=on}} in diameter. Outward from here, ejecta extend some {{convert|500|km|mi|abbr=on}} from the foot of the mountains and form a rough surface with hummocks and with features radially aligned towards the center.

The [[Apollo program]] did not sample rocks from Mare Orientale so its precise age is not known. However, it is the Moon's most recent impact basin, probably younger than the [[Mare Imbrium|Imbrium Basin]], which is about 3.85 billion years old, with an estimated age of around 3.7–3.8 billion years.{{Cite journal |last=Robbins |first=Stuart J. |date=2022-12-01 |title=Inconsistency between the Ancient Mars and Moon Impact Records of Megameter-scale Craters |journal=The Planetary Science Journal |volume=3 |issue=12 |pages=274 |doi=10.3847/PSJ/aca282 |doi-access=free |bibcode=2022PSJ.....3..274R |issn=2632-3338}} The surrounding basin material is of the [[Lower Imbrian]] [[epoch (geology)|epoch]] with the mare material being of the [[Upper Imbrian]] epoch.{{cite web |url=http://www.rasc.ca/sites/default/files/IWLOP2013c.pdf |title=The Isabel Williamson Lunar Observing Program |publisher=Royal Astronomical Society of Canada |date=March 2013 |access-date=29 October 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130705092307/http://www.rasc.ca/sites/default/files/IWLOP2013c.pdf |archive-date=5 July 2013 }}[https://pubs.er.usgs.gov/publication/pp1348 The geologic history of the Moon]. [[USGS]] Professional Paper 1348. By [[Don Wilhelms|Don E. Wilhelms]], John F. McCauley, and Newell J. Trask. U.S. Government Printing Office, Washington: 1987. Chapter 10.

The [[Apollo program]] did not sample rocks from Mare Orientale, so its precise age is not known. However, it is the Moon's most recent impact basin, likely younger than the [[Mare Imbrium|Imbrium Basin]], which is about 3.85 billion years old, with an estimated age of around 3.7–3.8 billion years.{{Cite journal |last=Robbins |first=Stuart J. |date=2022-12-01 |title=Inconsistency between the Ancient Mars and Moon Impact Records of Megameter-scale Craters |journal=The Planetary Science Journal |volume=3 |issue=12 |pages=274 |doi=10.3847/PSJ/aca282 |doi-access=free |bibcode=2022PSJ.....3..274R |issn=2632-3338}} The surrounding basin material is of the [[Lower Imbrian]] [[epoch (geology)|epoch]] with the mare material being of the [[Upper Imbrian]] epoch.{{cite web |url=http://www.rasc.ca/sites/default/files/IWLOP2013c.pdf |title=The Isabel Williamson Lunar Observing Program |publisher=Royal Astronomical Society of Canada |date=March 2013 |access-date=29 October 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130705092307/http://www.rasc.ca/sites/default/files/IWLOP2013c.pdf |archive-date=5 July 2013 }}[https://pubs.er.usgs.gov/publication/pp1348 The geologic history of the Moon]. [[USGS]] Professional Paper 1348. By [[Don Wilhelms|Don E. Wilhelms]], John F. McCauley, and Newell J. Trask. U.S. Government Printing Office, Washington: 1987. Chapter 10.

Global seismic shaking following the impact that created the basin has been credited with the levelling of almost all slopes steeper than 35° in layers of Imbrian age and older on the Moon.{{cite journal |date=2016 |first1=Mikhail A. |last1=Kreslavsky |first2=James W. |last2=Head |title=The steepest slopes on the Moon from Lunar Orbiter Laser Altimeter (LOLA) Data: Spatial Distribution and Correlation with Geologic Features |pages=329–336 |doi=10.1016/j.icarus.2016.02.036 |journal=Icarus |eissn=1090-2643 |volume=273|bibcode=2016Icar..273..329K |doi-access=free }}

Global seismic shaking following the impact that created the basin has been credited with the levelling of almost all slopes steeper than 35° in layers of Imbrian age and older on the Moon.{{cite journal |date=2016 |first1=Mikhail A. |last1=Kreslavsky |first2=James W. |last2=Head |title=The steepest slopes on the Moon from Lunar Orbiter Laser Altimeter (LOLA) Data: Spatial Distribution and Correlation with Geologic Features |pages=329–336 |doi=10.1016/j.icarus.2016.02.036 |journal=Icarus |eissn=1090-2643 |volume=273|bibcode=2016Icar..273..329K |doi-access=free }}