Editing Great Red Spot (section)

==Observation history==

=== First observations ===
[[File:Le osservazioni astronomiche - Giove.jpg|thumb|right|[[Donato Creti]]'s 1711 painting "Jupiter", the first depiction of a large spot on Jupiter as red]]
[[File:Jupiter Great Red Spot Elger November 1881.png|thumb|A sketch of Jupiter made by [[Thomas Gwyn Elger]] in November 1881, showing the Great Red Spot]]
The Great Red Spot may have existed before 1665, but it could be that the present spot was first seen only in 1830, and was well studied only after a prominent appearance in 1879. The storm that was seen in the 17th century may have been different from the storm that exists today.<ref>{{cite web |url=https://www.nasa.gov/feature/goddard/jupiter-s-great-red-spot-a-swirling-mystery |author=Karl Hille |date=2015-08-04 |title=Jupiter's Great Red Spot: A Swirling Mystery |website=[[NASA]] |access-date=2017-11-18}}</ref> A long gap separates its period of current study after 1830 from the 17th century discovery. It is unknown whether the original spot dissipated and reformed, whether it faded away, or whether observers simply failed to study and record it.{{sfnp|Beebe|1997|pp=38–41}}

The first sighting of the Great Red Spot is often credited to [[Robert Hooke]], who described a spot on the planet in May 1664.<ref name="aps-hooke-cassini"/> However, it is likely that Hooke's spot was not only in another belt altogether (the North Equatorial Belt, as opposed to the current Great Red Spot in the [[South Equatorial Belt]]), but also that it was in the shadow of a transiting moon, most likely [[Callisto (moon)|Callisto]].<ref name="aps-hooke-cassini">{{Cite web |title=May 1664: Hooke vs. Cassini: Who Discovered Jupiter's Red Spot? {{!}} This Month in Physics History |url=http://www.aps.org/publications/apsnews/202005/history.cfm |access-date=2021-12-29 |website=[[American Physical Society]] }}</ref> In the following year, [[Giovanni Cassini]] describes a "a permanent [spot] which was often seen to return in the same place with the same size and shape", calculating its rotation period to be {{nowrap|9 h 56 min}}.<ref name="aps-hooke-cassini"/>{{sfnp|Rogers|1995|p=6}} With fluctuations in visibility, Cassini's spot was observed from 1665 to 1713, but the 48-year observational gap makes the identity of the two spots inconclusive. Because of the older spot's shorter observational history and slower motion than the modern spot, it is difficult to conclude that they are the same.{{sfnp|Rogers|1995|p=188}}

A minor mystery concerns a Jovian spot depicted in a 1711 canvas by [[Donato Creti]], which is exhibited in the [[Vatican City|Vatican]].<ref>{{cite web |author=Staff |year=2003 |url=https://www.museivaticani.va/content/museivaticani/en/collezioni/musei/la-pinacoteca/sala-xv---secolo-xviii/donato-creti--osservazioni-astronomiche.html |title=Donato Creti, Astronomical observations |publisher=[[Vatican Museums]] |access-date=2019-12-16 }}</ref>{{sfnp|Hockey|1999|pp=40–41}} Part of a series of panels in which different (magnified) heavenly bodies serve as backdrops for various [[Italy|Italian]] scenes, and all overseen by the astronomer [[Eustachio Manfredi]] for accuracy, Creti's painting is the first known depiction of a large spot on Jupiter as red (albeit raised to the Jovian northern hemisphere due to an optical inversion inherent to the era's telescopes). No Jovian feature was explicitly described in writing as red before the late 19th century.{{sfnp|Hockey|1999|pp=40–41}}

The Great Red Spot has been frequently observed since 5 September 1831, with over 60 observations recorded by 1879, when it came into popular prominence.<ref name="Denning">{{cite journal |last1=Denning |first1=William Frederick |title=Early history of the great red spot on Jupiter |journal=Monthly Notices of the Royal Astronomical Society |date=June 1899 |volume=59 |issue=10 |page=574 |doi=10.1093/mnras/59.10.574 |publisher=Royal Astronomical Society |bibcode=1899MNRAS..59..574D|doi-access=free }}</ref> Since then, it has been under continuous observation.

A 2024 study of historical observations suggests that the "permanent spot" observed from 1665 to 1713 may not be the same as the modern Great Red Spot observed since 1831. It is suggested that the original spot disappeared, and later another spot formed, which is the one seen today.<ref name="Sánchez-Lavega2024"/>

===Late 20th and 21st centuries===
[[Image:Great Red Spot From Voyager 1.jpg|thumb|left|A wide view of Jupiter and the Great Red Spot as seen from ''[[Voyager 1]]'' in 1979.]]
On 25 February 1979,{{sfnp|Smith|1979|pp=951–972}} when the ''[[Voyager 1]]'' spacecraft was {{convert|9200000|km|mi|abbr=on}} from Jupiter, it transmitted the first detailed image of the Great Red Spot. Cloud details as small as {{convert|160|km|mi|-1|abbr=on}} across were visible. The colorful, wavy cloud pattern seen to the left (west) of the Red Spot is a region of extraordinarily complex and variable wave motion.

In the 21st century, the major diameter of the Great Red Spot has been observed to be shrinking. In 2004 its length was about half that of a century earlier, when it reached a size of {{convert|40,000|km|mi|abbr=on}}, about three times the diameter of Earth. At the present rate of reduction, it will become circular by 2040. 
[[File:Jupiter GRS Changes.png|thumb|A sequence of images of Jupiter showing the shrinking and rounding of the GRS, between 2021 and 2025. Captured with an 8" untracked Dobsonian telescope.]]
It is not known how long the spot will last, or whether the change is a result of periodic fluctuations.<ref>{{cite journal |last=Beatty |first=J. Kelly |year=2002 |title=Jupiter's Shrinking Red Spot |url=http://www.saburchill.com/HOS/astronomy/034.html |journal=Sky and Telescope |volume=103 |issue=4 |page=24 |bibcode=2002S&T...103d..24B |access-date=2007-06-21 |archive-date=2011-05-27 |archive-url=https://web.archive.org/web/20110527081602/http://www.saburchill.com/HOS/astronomy/034.html |url-status=dead }}</ref> In 2019, the spot began "flaking" at its edge, with fragments of the storm spinning off and dissipating.<ref name="disintegrating">{{cite web |author=Paul Scott Anderson |date=10 June 2019 |title=Is Jupiter's Great Red Spot disintegrating? |url=https://earthsky.org/space/is-jupiters-great-red-spot-disintegrating |access-date=2 July 2019 |publisher=EarthSky}}</ref> The shrinking and "flaking" fueled speculation from some astronomers that the spot could dissipate within decades.<ref>{{cite web |last1=Urrutia |first1=Doris Elin |title=Jupiter's Great Red Spot Could Disappear Within 20 Years |website=[[Space.com]] |date=21 February 2018 |url=https://www.space.com/39764-jupiter-great-red-spot-could-disappear.html |access-date=30 April 2023}}</ref> However, other astronomers believe the apparent size of the spot reflects its cloud coverage and not the size of the underlying vortex, and also that the flaking events can be explained by interactions with other cyclones or anticyclones, including incomplete absorptions of smaller systems; this might mean that the Great Red Spot is not in danger of dissipating.<ref name="may not">{{cite web |author=Philip Marcus |date=26 November 2019 |title=Jupiter's Great Red Spot may not be disappearing |url=https://astronomy.com/news/2019/11/jupiters-great-red-spot-is-not-disappearing |access-date=25 December 2020 |publisher=Astronomy}}</ref>

A smaller spot, designated [[Oval BA]], which formed in March 2000 from the merging of three white ovals,<ref>{{cite journal | url=https://www.sciencedirect.com/science/article/abs/pii/S0019103500965485 |first1=Agustín |last1=Sanchez-Lavega  |display-authors=etal |date=February 2001 |title=The Merger of Two Giant Anticyclones in the Atmosphere of Jupiter |journal=[[Icarus (journal)|Icarus]] |volume=149 |issue=2 |pages=491–495 |bibcode=2001Icar..149..491S |doi=10.1006/icar.2000.6548}}</ref> has turned reddish in color. Astronomers have named it the ''Little Red Spot'' or ''Red Jr''. As of 5 June 2006, the Great Red Spot and Oval BA appeared to be approaching convergence.<ref>{{cite web |last=Phillips |first=Tony |title=Huge Storms Converge |url=https://science.nasa.gov/headlines/y2006/05jun_redperil.htm |archive-url=https://web.archive.org/web/20070202190145/https://science.nasa.gov/headlines/y2006/05jun_redperil.htm |archive-date=2007-02-02 |access-date=2007-01-08 |publisher=Science@NASA}}</ref> The storms pass each other about every two years, but the passings of 2002 and 2004 were of little significance.{{cn|date=March 2025}} [[Amy Simon|Amy Simon-Miller]], of the [[Goddard Space Flight Center]], predicted the storms would have their closest passing on 4 July 2006.{{cn|date=March 2025}} She worked with [[Imke de Pater]] and Phil Marcus of [[University of California, Berkeley|UC Berkeley]] as well as a team of professional astronomers beginning in April 2006 to study the storms using the [[Hubble Space Telescope]]; on 20 July 2006, the two storms were photographed passing each other by the [[Gemini Observatory]] without converging.<ref>{{cite news |last=Michaud |first=Peter |title=Gemini Captures Close Encounter of Jupiter's Red Spots |publisher=Gemini Observatory |url=http://www.gemini.edu/index.php?option=content&task=view&id=196 |access-date=2007-06-15}}</ref> In May 2008, a third storm turned red.<ref>{{cite magazine |last=Shiga |first=David |title=Third red spot erupts on Jupiter |url=https://www.newscientist.com/article/dn13963-third-red-spot-erupts-on-jupiter/ |magazine=New Scientist |access-date=2008-05-23}}</ref>

The [[Juno (spacecraft)|''Juno'' spacecraft]], which entered into a polar orbit around Jupiter in 2016, flew over the Great Red Spot upon its close approach to Jupiter on 11 July 2017, taking several images of the storm from a distance of about {{convert|5000|mi|km|abbr=on|order=flip}} above the surface.<ref name="junospots"/><ref>{{cite web |last=Chang |first=Kenneth |date=2016-07-05 |title=NASA's Juno Spacecraft Enters Into Orbit Around Jupiter |url=https://www.nytimes.com/2016/07/05/science/juno-enters-jupiters-orbit-capping-5-year-voyage.html |access-date=2017-07-12 |website=[[The New York Times]]}}</ref> Over the duration of the ''Juno'' mission, the spacecraft continued to study the composition and evolution of Jupiter's atmosphere, especially its Great Red Spot.<ref name="junospots" />

The Great Red Spot should not be confused with the Great Dark Spot, a feature observed near the northern pole of Jupiter in 2000 with the ''[[Cassini–Huygens]]'' spacecraft.<ref>{{cite news |last=Phillips |first=Tony |title=The Great Dark Spot |publisher=Science at NASA |url=https://science.nasa.gov/headlines/y2003/12mar_darkspot.htm |access-date=2007-06-20 |archive-url=https://web.archive.org/web/20070615100054/https://science.nasa.gov/headlines/y2003/12mar_darkspot.htm |archive-date=2007-06-15}}</ref> There is also a feature in the atmosphere of [[Neptune]] called the [[Great Dark Spot]]. The latter feature was imaged by ''[[Voyager 2]]'' in 1989 and may have been an atmospheric hole rather than a storm.{{cn|date=March 2025}} It disappeared by 1994, although a similar spot had appeared farther to the north.{{cn|date=March 2025}}