View source for Oceanus Procellarum

{{Short description|Vast lunar mare on the western edge of the near side of Earth's Moon}}
{{redirect-distinguish|Ocean of Storms|Sea of Storms (disambiguation){{!}}Sea of Storms}}
{{More citations needed|date=December 2009}}
[[File:Oceanus Procellarum Si Barbero Zetta Ferruggia.jpg|left|thumb|The 'oceanus' area in a Selenochromatic Image (Si); targeted some chromatic landmarks]]
{{Infobox Lunar mare
|name        = Oceanus Procellarum
|image       = [[File:Oceanus Procellarum (LRO).png|200px]]
|caption     = Most of the dark region is Oceanus Procellarum and smaller maria, such as [[Mare Imbrium|Imbrium]] and [[Mare Serenitatis|Serenitatis]], that sit within its ring. Left of the centerline is Procellarum proper.
|eponym      = Ocean of Storms
|coordinates = {{coord|18.4|N|57.4|W|globe:moon_type:landmark|display=inline,title}}
|diameter    = {{convert|2592|km|mi|abbr=on}}<ref name=USGS>{{cite web |title=Oceanus Procellarum |publisher=USGS Astrogeology |work=Gazetteer of Planetary Nomenclature |url=http://planetarynames.wr.usgs.gov/Feature/4395?__fsk=-380014324 |access-date=2010-08-23}}</ref>
}}
'''Oceanus Procellarum''' ({{IPAc-en|oʊ|'|s|iː|ə|n|ə|s|_|ˌ|p|r|ɒ|s|ɛ|ˈ|l|ɛər|ə|m}} {{respell|oh|SEE|ə|nəs|_|PROSS|el|AIR|əm}}; from {{langx|la|Ōceanus procellārum|lit=Ocean of Storms}}) is a vast [[lunar mare]] on the western edge of the [[near side of the Moon|near side of the]] [[Moon]]. It is the only one of the lunar maria to be called an "[[Oceanus]]" (ocean), due to its size: Oceanus Procellarum is the largest of the maria ("seas"), stretching more than {{convert|2500|km|abbr=on}} across its north–south axis and covering roughly {{convert|4000000|km2|abbr=on}}, accounting for 10.5% of the total lunar surface area.<ref name=":0" />

==Characteristics==
Like all lunar maria, Oceanus Procellarum was formed by ancient [[volcano|volcanic]] eruptions resulting in [[basalt]]ic floods that covered the region in a thick, nearly flat layer of solidified [[magma]]. Basalts in Oceanus Procellarum have been estimated to be as young as one billion years old.<ref>{{Cite web|last=Andrea Thompson 06 November 2008|title=Signs of Late Volcanism Seen on Moon|url=https://www.space.com/6071-signs-late-volcanism-moon.html|access-date=2021-05-07|website=Space.com|date=6 November 2008 |language=en}}</ref> Unlike the other lunar maria, however, Oceanus Procellarum may or may not be contained within a single, well-defined impact basin.

Around its edges lie many minor bays and seas, including [[Sinus Roris]] to the north, and [[Mare Nubium]], [[Mare Humorum]] and {{ill|Sinus Viscositatis|it}}<ref>{{cite web |title=Sinus Viscositatis |url=https://planetarynames.wr.usgs.gov/Feature/16118 |website=Planetary Names |publisher=[[US Geological Survey]] |access-date=January 6, 2024}}</ref> to the south. To the northeast, Oceanus Procellarum is separated from [[Mare Imbrium]] by the [[Montes Carpatus|Carpathian Mountains]]. On its north-west edge lies the 32&nbsp;km wide [[Aristarchus (crater)|Aristarchus ray crater]], the brightest feature on the Near side of the Moon.<ref>DK Space Encyclopedia: The Near Side of the Moon</ref> Also, the more-prominent ray-crater [[Copernicus (lunar crater)|Copernicus]] lies within the eastern edge of the mare, distinct with its bright ray materials sprawling over the darker material.<ref>{{Cite web|title=NASA – Copernicus|url=https://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lola-20100430-copernicus.html|access-date=2021-05-07|website=www.nasa.gov|language=en|archive-date=2021-12-14|archive-url=https://web.archive.org/web/20211214010757/https://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lola-20100430-copernicus.html|url-status=dead}}</ref>

==Origin==
{{multiple image|total_width=600|align=center
|title=Moon – Oceanus Procellarum ("Ocean of Storms") |width1=614 |height1=228 |image1=14-236-LunarGrailMission-OceanusProcellarum-Rifts-Overall-20141001.jpg|caption1=Ancient [[rift valley]]s – rectangular structure (visible – topography – [[Gravity Recovery and Interior Laboratory|GRAIL gravity gradients]]) (October 1, 2014)|width2=1500  |height2=1500 |image2=PIA18822-LunarGrailMission-OceanusProcellarum-Rifts-Overall-20141001.jpg|caption2=Ancient [[rift valley]]s – context|width3=1546 |height3=905 |image3=PIA18821-LunarGrailMission-OceanusProcellarum-Rifts-Closeup-20141001.jpg|caption3=Ancient [[rift valley]]s – closeup (artist's concept)}}
[[File:Procellarum Rifts.tif|thumb|Gravity anomalies (red) bordering the Procellarum region overlaid on a global elevation map]]

There are several hypotheses about the origin of Oceanus Procellarum and a related asymmetry between the near and far sides of the Moon. One of the most likely is that Procellarum was a result of an ancient giant impact on the near side of the Moon. The size of the impact basin has been estimated to be more than 3,000 kilometers, which would make it [[List of largest craters in the Solar System|one of the three largest craters in the Solar System]].<ref name=":0">{{Cite web|last=October 2012|first=Charles Q. Choi 29|title=Moon's Mysterious 'Ocean of Storms' Explained|url=https://www.space.com/18276-moon-dark-spot-ocean-storms.html|access-date=2021-05-07|website=Space.com|date=29 October 2012 |language=en}}</ref> 

The impact likely happened very early in the Moon's history: at the time when [[Lunar magma ocean|magma ocean]] still existed or just ceased to exist. It deposited 5–30&nbsp;km of crustal material on the far side forming highlands. If this is the case, all impact related structures such as crater [[Impact crater|rim]], central peak etc. have been obliterated by later impacts and [[volcanism]]. One piece of evidence in support of this hypothesis is concentration of incompatible elements ([[KREEP]]) and low calcium [[pyroxene]] around Oceanus Procellarum.<ref name=Nakamura2012>{{Cite journal | last1 = Nakamura | first1 = R. | last2 = Yamamoto | first2 = S. | last3 = Matsunaga | first3 = T. | last4 = Ishihara | first4 = Y. | last5 = Morota | first5 = T. | last6 = Hiroi | first6 = T. | last7 = Takeda | first7 = H. | last8 = Ogawa | first8 = Y. | last9 = Yokota | first9 = Y. | last10 = Hirata | doi = 10.1038/NGEO1614 | first10 = N. | last11 = Ohtake | first11 = M. | last12 = Saiki | first12 = K. | title = Compositional evidence for an impact origin of the Moon's Procellarum basin | journal = Nature Geoscience | volume = 5 | issue = 11 | pages = 775 | year = 2012 | bibcode = 2012NatGe...5..775N }}</ref><ref name=Byrne2007>{{Cite journal | last1 = Byrne | first1 = C. J. | title = A Large Basin on the Near Side of the Moon | doi = 10.1007/s11038-007-9225-8 | journal = Earth, Moon, and Planets | volume = 101 | issue = 3–4 | pages = 153–188 | year = 2008 |bibcode = 2007EM&P..101..153B | s2cid = 121092521 }}</ref>

Procellarum may have also been formed by spatially inhomogeneous heating during the Moon's formation.<ref name=Nakamura2012/> The GRAIL mission, which mapped the gravity gradients of the Moon, found square formations resembling rift valleys surrounding the region beneath the lava plains, suggesting the basin was formed by heating and cooling of the lunar surface by internal processes rather than by an impact, which would have left a round crater.<ref name=NASA2014>{{cite press release |author=<!--Staff writer(s); no by-line.--> |title=NASA Mission Points to Origin of "Ocean of Storms" on Earth's Moon |url=http://www.nasa.gov/press/2014/october/nasa-mission-points-to-origin-of-ocean-of-storms-on-earth-s-moon |agency=NASA |date=2014-10-01 |access-date=2014-10-02}}</ref>

Other hypotheses include a late accretion of a companion Moon on the far side. The latter postulates that in addition to the present Moon, another smaller (about 1,200&nbsp;km in diameter) moon was formed from debris of the [[giant-impact hypothesis|giant impact]]. After a few tens of millions of years it collided with the Moon and due to a small collisional velocity simply piled up on one side of the Moon forming what is now known as far side [[Lunar highlands|highlands]].<ref name=Jutzi2011>{{Cite journal | last1 = Jutzi | first1 = M. | last2 = Asphaug | first2 = E. | doi = 10.1038/nature10289 | title = Forming the lunar farside highlands by accretion of a companion moon | journal = Nature | volume = 476 | issue = 7358 | pages = 69–72 | year = 2011 | pmid =  21814278| bibcode = 2011Natur.476...69J | s2cid = 84558 }}</ref>

==Late lunar volcanism==
Relatively recent (less than 2 bya) volcanic activity had been suspected in the Oceanus Procellarum due to the presence of relatively uneroded features. The 2020 Chang'e-5 sample return mission provided constraints on the age of Oceanus Procellarum, finding it to be 1963 ± 57 million years old – over a billion years younger than any other previously returned lunar sample. Late lunar volcanic activity was considered surprising as the Moon is much smaller than Earth; interior heat necessary for volcanism should have been lost three billion years ago, so volcanic rocks as late as those found in Oceanus Procellarum must require additional heat sources. 

Previous studies suggested that Oceanus Procellarum should have high concentrations of the heat-producing elements such as potassium, thorium, and uranium{{efn|due to the abundance of their radioactive isotopes providing heat from decay}}, but samples returned showed that the concentration of suspected radioactive elements is much lower than necessary to provide prolonged heating.<ref name="change-5-no-radioactive-elements">{{Cite journal |last1=Che |first1=Xiaochao |last2=Nemchin |first2=Alexander |last3=Liu |first3=Dunyi |last4=Long |first4=Tao |last5=Wang |first5=Chen |last6=Norman |first6=Marc D. |last7=Joy |first7=Katherine H. |author7-link=Katherine Joy |last8=Tartese |first8=Romain |last9=Head |first9=James |last10=Jolliff |first10=Bradley |last11=Snape |first11=Joshua F. |display-authors=etal|date=2021-11-12 |title=Age and composition of young basalts on the Moon, measured from samples returned by Chang'e-5 |url=https://www.science.org/doi/10.1126/science.abl7957 |journal=Science |language=en |volume=374 |issue=6569 |pages=887–890 |doi=10.1126/science.abl7957 |pmid=34618547 |bibcode=2021Sci...374..887C |s2cid=238474681 |issn=0036-8075|url-access=subscription }}</ref>

==Exploration==
The [[robotic spacecraft|robotic]] lunar [[space probe|probes]] [[Luna 9]], [[Luna 13]], [[Surveyor 1]] and [[Surveyor 3]] landed in Oceanus Procellarum. Luna 9 landed southwest of [[Galilaei (lunar crater)|Galilaei]] crater in 1966.  Luna 13 landed southeast of [[Seleucus (crater)|Seleucus]] crater, later in 1966. Surveyor 1 landed north of [[Flamsteed (crater)|Flamsteed]] crater (within the larger Flamsteed P) in 1966, and Surveyor 3 landed in 1967. The [[China|Chinese]] probe [[Chang'e 5]] landed at Statio Tianchuan on [[Mons Rümker]] in Oceanus Procellarum in December 2020 and collected {{convert|1.73|kg|lb|abbr=on}} of lunar rock samples.<ref>{{cite web |last=Jones |first=Andrew |url=https://www.space.com/china-chang-e-5-moon-landing-site-name |title=China's Chang'e 5 moon landing site finally has a name |work=[[Space.com]] |date=8 July 2021 |access-date=9 July 2021}}</ref><ref name="AJ23112020">{{Cite web|url=https://www.cnn.com/2020/12/16/asia/china-lunar-probe-intl/index.html|title=China's Chang'e-5 mission returns to Earth with moon samples|author=Jennifer Hauser and Zamira Rahim|website=CNN|date=16 December 2020 }}</ref>[[File:Apollo 12 landing site 3154 h2.jpg|thumb|176x176px|Image of [[Apollo 12]] landing site (center) used in mission planning (1.75 × 1.75 km)]]During the Apollo program, flight operations planners were concerned about having the optimum lighting conditions at the landing site, hence the alternative target sites moved progressively westward, following the terminator. A delay of two days for weather or equipment reasons would have sent Apollo 11 to [[Sinus Medii]] (designated ALS3) instead of ALS2—[[Mare Tranquillitatis]]; another two-day delay would have resulted in ALS5, a site in Oceanus Procellarum, being targeted.

During the November 1969 [[Apollo 12]] mission, [[astronaut]]s (Charles) [[Pete Conrad]] and [[Alan Bean]] landed the Lunar Module (LM) ''Intrepid'' nearly 165 meters from Surveyor 3 in Oceanus Procellarum.<ref>{{Cite web|title=Apollo 12 Mission Overview|url=https://www.lpi.usra.edu/lunar/missions/apollo/apollo_12/|access-date=2021-04-25|website=www.lpi.usra.edu}}</ref> Their landing site has become known as Statio Cognitum (Latin, "to be known from experience").<ref>{{Cite web|title=Pinpoint Landing on the Ocean of Storms {{!}} Lunar Reconnaissance Orbiter Camera|url=http://lroc.sese.asu.edu/posts/401|access-date=2021-04-25|website=lroc.sese.asu.edu}}</ref>

==In popular culture==
*In the 2004 album ''[[Sirens (Astarte album)|Sirens]]'' by Greek metal band [[Astarte (band)|Astarte]], there is a song named after the lunar mare.

==See also==
* [[Canceled Apollo missions#Follow-on lunar missions|Apollo 18]]
*[[Aristarchus (crater)]]
*[[Human Lunar Return study]]
*[[Mare Cognitum]]
*[[Volcanism on the Moon]]

==References==
{{Commons category|Oceanus Procellarum}}
{{Reflist}}
{{notelist}}

== External links ==

* {{Cite web |last=Ferruggia |first=Aldo |title=Selenochromatica |url=https://www.gawh.it/main/selenocromatica}}
{{Lunar maria}}
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[[Category:Maria on the Moon|Procellarum]]
[[Category:Apollo 12]]