Editing Great Red Spot (section)

==Color and composition==
It is not known what causes the Great Red Spot's reddish color. Hypotheses supported by laboratory experiments suppose that it may be caused by chemical products created by the solar ultraviolet irradiation of [[ammonium hydrosulfide]]<ref>{{cite web|url=https://www.nasa.gov/feature/goddard/jupiter-s-great-red-spot-a-swirling-mystery|title=Jupiter's Great Red Spot: A Swirling Mystery|publisher=[[NASA]]|quote=[[Goddard Institute for Space Studies|Goddard]] scientists Mark Loeffler and Reggie Hudson have been performing laboratory studies to investigate whether cosmic rays, one type of radiation that strikes Jupiter's clouds, can chemically alter ammonium hydrosulfide to produce new compounds that could explain the spot's color. |date=August 4, 2015}}</ref> and the organic compound [[acetylene]], which produces a reddish material—likely complex organic compounds called [[tholin]]s.<ref name="Hudson2018">{{cite journal |last1=Loeffer |first1=Mark J. |last2=Hudson |first2=Reggie L. |title=Coloring Jupiter's clouds: Radiolysis of ammonium hydrosulfide (NH4SH) |journal=Icarus |year=2018 |volume=302 |pages=418–425 |doi=10.1016/j.icarus.2017.10.041|bibcode=2018Icar..302..418L }}</ref> The high altitude of the compounds may also contribute to the coloring.<ref name="EarthSky">{{cite web |title=What makes Jupiter's Red Spot red? |date=2014-11-11 |url=https://earthsky.org/space/what-makes-jupiters-red-spot-red |access-date=2019-03-13 |publisher=[[EarthSky]]}}</ref>

The Great Red Spot varies greatly in hue, from almost brick-red to pale salmon or even white. The spot occasionally disappears, becoming evident only through the Red Spot Hollow, which is its location in the [[South Equatorial Belt]] (SEB). Its visibility is apparently coupled to the SEB: when the belt is bright white, the spot tends to be dark, and when it is dark, the spot is usually light. These periods when the spot is dark or light occur at irregular intervals: between 1947 and 1997, the spot was darkest in the periods 1961–1966, 1968–1975, 1989–1990, and 1992–1993.{{sfnp|Beebe|1997|pp=38–41}}