Enceladus - Revision history

FredericBernard: /* Atmosphere */ Wikify

2019-02-20T15:28:52Z

Atmosphere: Wikify

DavidB4-bot: /* Orbital characteristics */HTTP --> HTTPS [#1], replaced: http://www.britannica.com → https://www.britannica.com

2018-09-26T15:40:51Z

Orbital characteristics: HTTP --> HTTPS [#1], replaced: http://www.britannica.com → https://www.britannica.com

JDano: /* Discovery and naming */ link

2017-03-17T03:17:02Z

Discovery and naming: link

DavidB4-bot: Spelling/Grammar Check, typos fixed: particlate → particulate

2016-07-18T13:48:23Z

Spelling/Grammar Check, typos fixed: particlate → particulate

DavidB4-bot: clean up & uniformity

2016-07-13T12:00:05Z

clean up & uniformity

ScKinney: /* Surface */

2015-01-28T00:25:37Z

Surface

TerryH: /* Atmosphere */ Spelling

2008-06-19T20:46:23Z

Atmosphere: Spelling

TerryH at 03:18, June 19, 2008

2008-06-19T03:18:00Z

TerryH at 19:23, June 18, 2008

2008-06-18T19:23:18Z

TerryH at 17:52, June 18, 2008

2008-06-18T17:52:51Z

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 === Atmosphere ===
-[[Image:Enceladus atmosphere not global.jpg|thumb|200px|left|Stellar occultation reveals that the Enceladan atmosphere is local to the south pole, not global.]]Enceladus has a thin but significant atmosphere, mostly of [[water]] vapor. The chief evidence for this is a deflection of the magnetic field of Saturn as Enceladus moves through it. This atmosphere requires continual replenishment from the cryovolcanic activity.<ref name=Porco/><ref name=atmosphere1>"[http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=553 Cassini Finds an Atmosphere on Saturn's Moon Enceladus]." Press release, [[Jet Propulsion Laboratory|JPL]], March 16, 2005. Accessed June 17, 2008.</ref> In addition, the occultation of the star Bellatrix on July 11, 2005 revealed that the atmosphere is not global in scope, but is probably local to the south polar region, where most of the venting takes place.<ref name=atmosphere2>"[http://photojournal.jpl.nasa.gov/catalog/PIA03552 Enceladus Atmosphere Not Global]." [[Jet Propulsion Laboratory|JPL]], [[National Aeronautics and Space Administration|NASA]], August 30, 2005. Accessed June 17, 2008.</ref>
+[[Image:Enceladus atmosphere not global.jpg|thumb|200px|left|Stellar occultation reveals that the Enceladan atmosphere is local to the south pole, not global.]]Enceladus has a thin but significant atmosphere, mostly of [[water]] vapor. The chief evidence for this is a deflection of the magnetic field of Saturn as Enceladus moves through it. This atmosphere requires continual replenishment from the cryovolcanic activity.<ref name=Porco/><ref name=atmosphere1>"[http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=553 Cassini Finds an Atmosphere on Saturn's Moon Enceladus]." Press release, [[Jet Propulsion Laboratory|JPL]], March 16, 2005. Accessed June 17, 2008.</ref> In addition, the occultation of the star [[Bellatrix]] on July 11, 2005 revealed that the atmosphere is not global in scope, but is probably local to the south polar region, where most of the venting takes place.<ref name=atmosphere2>"[http://photojournal.jpl.nasa.gov/catalog/PIA03552 Enceladus Atmosphere Not Global]." [[Jet Propulsion Laboratory|JPL]], [[National Aeronautics and Space Administration|NASA]], August 30, 2005. Accessed June 17, 2008.</ref>
 === Magnetosphere ===

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 == Orbital characteristics ==
-Enceladus is in a very slightly eccentric orbit around Saturn, at an average distance of 238,020&nbsp;km,<ref name=saturnsatfact/><ref name=Britannica>Hubbard, William B. "[http://www.britannica.com/eb/article-9032584 Enceladus]." Encyclopædia Britannica. 2008. Encyclopædia Britannica Online. 18 June 2008.</ref> or within the most dense region of the E ring of Saturn.<ref name=Britannica/>
+Enceladus is in a very slightly eccentric orbit around Saturn, at an average distance of 238,020&nbsp;km,<ref name=saturnsatfact/><ref name=Britannica>Hubbard, William B. "[https://www.britannica.com/eb/article-9032584 Enceladus]." Encyclopædia Britannica. 2008. Encyclopædia Britannica Online. 18 June 2008.</ref> or within the most dense region of the E ring of Saturn.<ref name=Britannica/>
 Enceladus might or might not be in a 1:2 [[orbital resonance]] with [[Dione]].<ref name=Britannica/><ref name=Arnett/><ref name=Porco>Porco, C.C., Helfenstein, P., Thomas, P.C., ''et al.'' "[http://www.sciencemag.org/cgi/content/abstract/311/5766/1393 Cassini Observes the Active South Pole of Enceladus]." ''Science'' 311(5766):1393-1401, March 10, 2006. {{doi|10.1126/science.1123013}} Accessed June 18, 2008.</ref> The sidereal month of Dione is slightly less than twice that of Enceladus.

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 Sir [[John Herschel]], his son, suggested the current names of the seven largest satellites of Saturn, including Enceladus. [[Titan (moon)|Titan]] received a generic name, and the other six received names of the Titans of mythology. Enceladus was a giant who fell in battle against Athena in the Titan-Olympian War.<ref name=Lasell>Lassell, William. "[http://articles.adsabs.harvard.edu/full/seri/MNRAS/0008//0000042.000.html Satellites of Saturn]." ''Monthly Notices of the Royal Astronomical Society'', 8(3):42-43, January 14, 1848. Accessed June 4, 2008.</ref>
-According to legend, Athena buried Enceladus by heaping dirt on him where he fell. His burial mound is supposed to be the island of Sicily, and more specifically he lies beneath Mount Etna, which vents or erupts as he breathes.<ref name=usgs/><ref name=Arnett>Arnett, Bill. "[http://www.nineplanets.org/enceladus.html Entry for Enceladus]." ''The <s>Nine</s> 8 Planets'', March 30, 2007. Accessed June 17, 2008.</ref> Considering the findings from the exploration of Enceladus by Voyagers 1 and 2 and the [[Cassini-Huygens Mission|Cassini]] orbiter, Enceladus is a more apt name for this moon than Sir John Herschel might have supposed.
+According to legend, Athena buried Enceladus by heaping dirt on him where he fell. His burial mound is supposed to be the island of Sicily, and more specifically he lies beneath [[Mount Etna]], which vents or erupts as he breathes.<ref name=usgs/><ref name=Arnett>Arnett, Bill. "[http://www.nineplanets.org/enceladus.html Entry for Enceladus]." ''The <s>Nine</s> 8 Planets'', March 30, 2007. Accessed June 17, 2008.</ref> Considering the findings from the exploration of Enceladus by Voyagers 1 and 2 and the [[Cassini-Huygens Mission|Cassini]] orbiter, Enceladus is a more apt name for this moon than Sir John Herschel might have supposed.
 == Orbital characteristics ==

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 [[Voyager 1]] made the first close rendezvous with Enceladus. [[Project Voyager]] mission controllers discerned from this encounter that Enceladus was in orbit around Saturn at the thickest portion of the E ring. [[Voyager 2]] revealed the surprising variation in the surface of Enceladus, with geologically "old" and "young" regions.<ref name=Britannica/>
-The [[Cassini-Huygens mission|Cassini]] orbiter, early in its mission, returned evidence of the volcanic activity of Enceladus and its possible role as the source of the particlate matter in the E ring.<ref name=Britannica/> Mission planners then scheduled many more rendezvous with Enceladus. With each encounter, Cassini returned ever more remarkable findings about Enceladus.
+The [[Cassini-Huygens mission|Cassini]] orbiter, early in its mission, returned evidence of the volcanic activity of Enceladus and its possible role as the source of the particulate matter in the E ring.<ref name=Britannica/> Mission planners then scheduled many more rendezvous with Enceladus. With each encounter, Cassini returned ever more remarkable findings about Enceladus.
 The Cassini-Huygens mission is now (June 17, 2008) about to begin its two-year extended mission. This mission will include even more rendezvous with this remarkable object.
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 {{reflist|2}}
 {{Solarsystem}}

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 |composition=Water ice, silicates<ref name=Hamilton2>Hamilton,Calvin J. "[http://solarviews.com/eng/enceladusgeyser.htm A Hot Start Might Explain Geysers on Enceladus]." ''Views of the Solar System'', 2007. Accessed June 18, 2008.</ref>
 |color=Light blue-white<ref name=Hamilton2/>
-|albedo=1.0<ref name=saturnsatfact/><ref name=Hamilton/><ref name=Britannica/>
+|albedo=1.0<ref name=Hamilton/><ref name=saturnsatfact/><ref name=Britannica/>
 }}'''Enceladus''' or '''Saturn II''' is the ninth known [[moon]] of [[Saturn]] and the seventh to be discovered. It is also one of three bodies in the [[solar system]] (other than [[Earth]]) known to be [[volcano|volcanically]] active. In fact, recent evidence suggests that Enceladus is the source of Saturn's E ring.
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 == Orbital characteristics ==
-Enceladus is in a very slightly eccentric orbit around Saturn, at an average distance of 238,020 km,<ref name=saturnsatfact/><ref name=Britannica>Hubbard, William B. "[http://www.britannica.com/eb/article-9032584 Enceladus]." Encyclopædia Britannica. 2008. Encyclopædia Britannica Online. 18 June 2008.</ref> or within the most dense region of the E ring of Saturn.<ref name=Britannica/>
+Enceladus is in a very slightly eccentric orbit around Saturn, at an average distance of 238,020&nbsp;km,<ref name=saturnsatfact/><ref name=Britannica>Hubbard, William B. "[http://www.britannica.com/eb/article-9032584 Enceladus]." Encyclopædia Britannica. 2008. Encyclopædia Britannica Online. 18 June 2008.</ref> or within the most dense region of the E ring of Saturn.<ref name=Britannica/>
-Enceladus might or might not be in a 1:2 [[orbital resonance]] with [[Dione]].<ref name=Arnett/><ref name=Britannica/><ref name=Porco>Porco, C.C., Helfenstein, P., Thomas, P.C., ''et al.'' "[http://www.sciencemag.org/cgi/content/abstract/311/5766/1393 Cassini Observes the Active South Pole of Enceladus]." ''Science'' 311(5766):1393-1401, March 10, 2006. {{doi|10.1126/science.1123013}} Accessed June 18, 2008.</ref> The sidereal month of Dione is slightly less than twice that of Enceladus.
+Enceladus might or might not be in a 1:2 [[orbital resonance]] with [[Dione]].<ref name=Britannica/><ref name=Arnett/><ref name=Porco>Porco, C.C., Helfenstein, P., Thomas, P.C., ''et al.'' "[http://www.sciencemag.org/cgi/content/abstract/311/5766/1393 Cassini Observes the Active South Pole of Enceladus]." ''Science'' 311(5766):1393-1401, March 10, 2006. {{doi|10.1126/science.1123013}} Accessed June 18, 2008.</ref> The sidereal month of Dione is slightly less than twice that of Enceladus.
 == Rotational characteristics ==
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 == Physical characteristics ==
-Enceladus has a density of 1.610 kg/m³, 60% greater than that of [[water]]. Hence it is likely composed of water ice and rock. With an albedo of unity or greater, Enceladus is the most reflective body in all the solar system.<ref name=Spencer/>
+Enceladus has a density of 1.610&nbsp;kg/m³, 60% greater than that of [[water]]. Hence it is likely composed of water ice and rock. With an albedo of unity or greater, Enceladus is the most reflective body in all the solar system.<ref name=Spencer/>
 === Surface ===
-Enceladus has at least five different types of terrain.<ref name=Hamilton/> Regions with impact craters having diameters of 35 km or less, alternate with other regions having no craters. Astronomers suspect extensive remodeling of the surface throughout Enceladus's history.<ref name=Britannica/>
+Enceladus has at least five different types of terrain.<ref name=Hamilton/> Regions with impact craters having diameters of 35&nbsp;km or less, alternate with other regions having no craters. Astronomers suspect extensive remodeling of the surface throughout Enceladus's history.<ref name=Britannica/>
 The most surprising finding is the south polar region. It contains multiple fissures, called "tiger stripes" because their appearance suggests the pelt of a [[tiger]]. These fissures radiate significant amounts of heat, with temperatures exceeding 145 K.<ref name=Spencer/> From these fissures, geysers discharge large amounts of water vapor and ice into space. Some of this remains as a tenuous, localized [[atmosphere]] (see below). Other particles escape Enceladus' gravity and thus contribute to the E ring of Saturn.<ref name=Porco/><ref name=Spahn>Spahn, F., Schmidt, J., Albers N., ''et al.'' "[http://www.sciencemag.org/cgi/content/abstract/311/5766/1416 Cassini Dust Measurements at Enceladus and Implications for the Origin of the E Ring]." ''Science'' 311(5766):1416-1418. {{doi|10.1126/science.1121375}} Accessed June 18, 2008.</ref><ref name=Hamilton1>Hamilton, Calvin J. "[http://solarviews.com/eng/enceladuswater.htm Radical! Liquid Water on Enceladus]." ''Views of the Solar System'', March 9, 2006. Accessed June 18, 2008.</ref>
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 == Problems for uniformitarian theories posed by Enceladus ==
-Enceladus shows many signs of having internal heat, while its inner companion [[Mimas]] does not. Yet Enceladus is more distant than Mimas from Saturn, and its orbit is less eccentric. That Mimas should have frozen solid, while Enceladus did not freeze and remains tectonically and volcanically active, defies explanation. Spencer ''et al''<ref name=Spencer/> have admitted this problem but suggested that forced libration might explain the heating. Yet if Enceladus changed its axis of rotation, as Nimmo and Pappalardo suggested<ref name=Nimmo/>, then the heat must have arisen ''before'' the libration.
+Enceladus shows many signs of having internal heat, while its inner companion [[Mimas]] does not. Yet Enceladus is more distant than Mimas from Saturn, and its orbit is less eccentric. That Mimas should have frozen solid, while Enceladus did not freeze and remains tectonically and volcanically active, defies explanation. Spencer ''et al''<ref name=Spencer/> have admitted this problem but suggested that forced libration might explain the heating. Yet if Enceladus changed its axis of rotation, as Nimmo and Pappalardo suggested,<ref name=Nimmo/> then the heat must have arisen ''before'' the libration.
 == Observation and Exploration ==

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 Enceladus has at least five different types of terrain.<ref name=Hamilton/> Regions with impact craters having diameters of 35 km or less, alternate with other regions having no craters. Astronomers suspect extensive remodeling of the surface throughout Enceladus's history.<ref name=Britannica/>
-The most surprising finding is the south polar region. It contains multiple fissures, called "tiger stripes" because their appearance suggests the pelt of a [[tiger]]. These fissures radiate significant amounts of heat, with temperatures exceeding 145 K.<ref name=Spencer/> From these fissures, geysers discharge large amounts of water vapor and ice into the sky. Some of this remains as a tenuous, localized [[atmosphere]] (see below). Other particles escape Enceladus' gravity and thus contribute to the E ring of Saturn.<ref name=Porco/><ref name=Spahn>Spahn, F., Schmidt, J., Albers N., ''et al.'' "[http://www.sciencemag.org/cgi/content/abstract/311/5766/1416 Cassini Dust Measurements at Enceladus and Implications for the Origin of the E Ring]." ''Science'' 311(5766):1416-1418. {{doi|10.1126/science.1121375}} Accessed June 18, 2008.</ref><ref name=Hamilton1>Hamilton, Calvin J. "[http://solarviews.com/eng/enceladuswater.htm Radical! Liquid Water on Enceladus]." ''Views of the Solar System'', March 9, 2006. Accessed June 18, 2008.</ref>
+The most surprising finding is the south polar region. It contains multiple fissures, called "tiger stripes" because their appearance suggests the pelt of a [[tiger]]. These fissures radiate significant amounts of heat, with temperatures exceeding 145 K.<ref name=Spencer/> From these fissures, geysers discharge large amounts of water vapor and ice into space. Some of this remains as a tenuous, localized [[atmosphere]] (see below). Other particles escape Enceladus' gravity and thus contribute to the E ring of Saturn.<ref name=Porco/><ref name=Spahn>Spahn, F., Schmidt, J., Albers N., ''et al.'' "[http://www.sciencemag.org/cgi/content/abstract/311/5766/1416 Cassini Dust Measurements at Enceladus and Implications for the Origin of the E Ring]." ''Science'' 311(5766):1416-1418. {{doi|10.1126/science.1121375}} Accessed June 18, 2008.</ref><ref name=Hamilton1>Hamilton, Calvin J. "[http://solarviews.com/eng/enceladuswater.htm Radical! Liquid Water on Enceladus]." ''Views of the Solar System'', March 9, 2006. Accessed June 18, 2008.</ref>
 Surprisingly, the E ring is not the only ring to receive contributions from Enceladus. Recent evidence now suggests that some of the ejected particles from Enceladus enter Saturn's magnetic field and eventually reach the A ring.<ref name=Farrell>Farrell, W.M., Kaiser, M.L., Gurnett, D.A., ''et al.'' "[http://www.agu.org/pubs/crossref/2008/2007GL032306.shtml Mass unloading along the inner edge of the Enceladus plasma torus]." ''Geophys. Res. Lett.'' 35(L02203), January 23, 2008. {{doi|10.1029/2007GL032306}} Accessed June 18, 2008.</ref><ref name=Hamilton3>Hamilton, Calvin J. "[http://solarviews.com/eng/giantsponge.htm Saturn's Giant Sponge]." ''Views of the Solar System'', February 5, 2008. Accessed June 18, 2008.</ref>

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 === Surface ===
-Enceladus has at least five different types of terrain.<ref name=Hamilton/> Regions with impact craters having diamters of 35 km or less, alternate with other regions having no craters. Astronomers suspect extensive remodeling of the surface throughout Enceladus's history.<ref name=Britannica/>
+Enceladus has at least five different types of terrain.<ref name=Hamilton/> Regions with impact craters having diameters of 35 km or less, alternate with other regions having no craters. Astronomers suspect extensive remodeling of the surface throughout Enceladus's history.<ref name=Britannica/>
 The most surprising finding is the south polar region. It contains multiple fissures, called "tiger stripes" because their appearance suggests the pelt of a [[tiger]]. These fissures radiate significant amounts of heat, with temperatures exceeding 145 K.<ref name=Spencer/> From these fissures, geysers discharge large amounts of water vapor and ice into the sky. Some of this remains as a tenuous, localized atmosphere (see below). Other particles escape Enceladus' gravity and thus contribute to the E ring of Saturn.<ref name=Porco/><ref name=Spahn>Spahn, F., Schmidt, J., Albers N., ''et al.'' "[http://www.sciencemag.org/cgi/content/abstract/311/5766/1416 Cassini Dust Measurements at Enceladus and Implications for the Origin of the E Ring]." ''Science'' 311(5766):1416-1418. {{doi|10.1126/science.1121375}} Accessed June 18, 2008.</ref><ref name=Hamilton1>Hamilton, Calvin J. "[http://solarviews.com/eng/enceladuswater.htm Radical! Liquid Water on Enceladus]." ''Views of the Solar System'', March 9, 2006. Accessed June 18, 2008.</ref>