Mare Orientale
Template:Short description Template:Redirect Template:Infobox Lunar mare
Mare Orientale Template:IPAc-en (Latin orientāle, the "eastern sea") is a lunar mare. It is located on the western border of the near side and far side of the Moon,Template:Sfn and is difficult to see from an Earthbound perspective. Images from spacecraft have revealed it to be one of the most striking large scale lunar features, resembling a target ring bullseye.
GeologyEdit
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.Template:SfnTemplate:Sfn The structure, with the flat plain of the mare in the center, is about Template:Convert across and was formed by the impact of an asteroid-sized object,<ref name=lunarorbiter>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=stardate>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> possibly Template:Convert in diameter and travelling at Template:Convert.<ref name="theconvo20161103">Template:Cite news</ref><ref name="Johnson20161028">Template:Cite journal</ref> Compared with most other lunar basins, Mare Orientale is less flooded by mare basalts, so that much of the basin structure is visible. The basalt in the central portion of the Orientale basin is probably less than Template:Convert in thickness which is much less than mare basins on the Earth-facing side of the Moon.<ref name=lunarorbiter /> 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, Template:Convert in diameter. Outward from here, ejecta extend some Template:Convert from the foot of the mountains and form a rough surface with hummocks and with features radially aligned towards the center.<ref name=lunarorbiter />
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 Imbrium Basin, which is about 3.85 billion years old,<ref name=lunarorbiter /> with an estimated age of around 3.7-3.8 billion years.<ref>Template:Cite journal</ref> The surrounding basin material is of the Lower Imbrian epoch with the mare material being of the Upper Imbrian epoch.<ref name=rasc>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>The geologic history of the Moon. USGS Professional Paper 1348. By Don E. Wilhelms, John F. McCauley, and Newell J. Trask. U.S. Government Printing Office, Washington: 1987. Chapter 10.</ref>
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.<ref>Template:Cite journal</ref>
Located at the antipode of Mare Orientale is Mare Marginis.
A mass concentration (mascon), or gravitational high, was identified in the center of Mare Orientale from Doppler tracking of the five Lunar Orbiter spacecraft in 1968.<ref>Template:Cite journal</ref> The mascon was confirmed and mapped at higher resolution with later orbiters such as Lunar Prospector and GRAIL.
Discovery and nameEdit
Mare Orientale is difficult to observe from Earth, as it lies at the extreme western edge of the near side. All that can be seen are the rough mountain ranges—the Montes Rook and the Montes Cordillera—and some glimpses of the dark mare material beyond them.Template:Sfn However, the Moon's libration means that on rare occasions Mare Orientale is turned slightly more toward the Earth, and becomes a little more discernible.Template:Sfn
Although various astronomers had observed hints of the mare, it was first fully described by the German astronomer Julius Franz in his 1906 book Der Mond ("The Moon"). Franz also gave the mare its name, the "Eastern Sea", as it was located on what the convention at the time considered was the eastern side of the Moon as viewed from Earth,Template:Sfn though it is the western side as viewed by an astronaut walking on the Moon. In 1961, however, the International Astronomical Union adopted the astronautic convention for East and West on the Moon and this limb became the western edge.Template:Sfn
The first detailed study of the Mare Orientale was by Hugh Percy Wilkins, who called it "Lunar Mare X".Template:Sfn Franz's discoveries were not well known,Template:Sfn and in the 1976 edition of his book Guide to the Moon, Patrick Moore claims that he and Wilkins discovered and named Mare Orientale in 1946. However, Moore credits Franz as discoverer in his 2009 Yearbook of Astronomy (p. 133–135).
GalleryEdit
- Orientale basin topo.jpg
Topographic map
- Orientale basin GRAIL gravity.jpg
Gravity map based on GRAIL
- Orientale Basin Clementine Mosaic Scle s21.tif
Albedo mosaic of Clementine images
- Mare Orientale LRO.jpg
- Mare Orientale location marked in cropped image of full moon.svg
Photograph from Earth at full moon with Mare Orientale marked on the limb
- Mare-Orientale-Artifacts Lat-28 Long-96.jpg
Dome-shaped hills at the southern edge of Mare Orientale Basin, possibly formed by lava flows.
- AS17-158-23902.jpg
Apollo 17 photographed eastern Mare Orientale in the faint light of earthshine.
See alsoEdit
- Volcanism on the Moon
- Burney basin – a structurally similar impact basin on Pluto