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| image=Titan Cassini 2006.jpg

| image=Titan Cassini 2006.jpg

| caption=Titan in true color. The color is of Titan's hazy [[atmosphere]].<ref name=Cassini>"[http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1992 Titanic complexity]," Space Science Institute, [[Jet Propulsion Laboratory]], [[NASA]], February 13, 2006. Accessed February 16, 2008.</ref>

| caption=Titan in true color. The color is of Titan's hazy [[atmosphere]].<ref name=Cassini>"[http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1992 Titanic complexity]," Space Science Institute, [[Jet Propulsion Laboratory]], [[NASA]], February 13, 2006. Accessed February 16, 2008.</ref>

| date=March 25, 1655<ref name=solarviews>Hamilton, Calvin J. "[http://solarviews.com/eng/titan.htm Saturn's Moon Titan]." ''SolarViews'', 2001. Accessed February 16, 2008.</ref>

| date=March 25, 1655<ref name=usgs>"[http://planetarynames.wr.usgs.gov/append7.html Gazetteer of Planetary Nomenclature: Planetary Body Names and Discoverers]." US Geological Survey, Jennifer Blue, ed. March 31, 2008. Accessed April 17, 2008.</ref><ref name=solarviews>Hamilton, Calvin J. "[http://solarviews.com/eng/titan.htm Saturn's Moon Titan]." ''SolarViews'', 2001. Accessed February 16, 2008.</ref>

| discname=[[Christiaan Huygens]]<ref name=solarviews/><ref name=Huygens1>"[http://www.esa.int/esaSC/SEMJRT57ESD_index_0.html Discoverer of Titan: Christiaan Huygens.]" ''ESA Space Science'', [[European Space Agency]], April 24, 2007. Accessed February 16, 2008.</ref>

| discname=[[Christiaan Huygens]]<ref name=usgs/><ref name=solarviews/><ref name=Huygens1>"[http://www.esa.int/esaSC/SEMJRT57ESD_index_0.html Discoverer of Titan: Christiaan Huygens.]" ''ESA Space Science'', [[European Space Agency]], April 24, 2007. Accessed February 16, 2008.</ref>

| origname=First generation of Greco-Roman gods

| origname=First generation of Greco-Roman gods

| primary=Saturn

| primary=Saturn

| color=Orange<ref name=Cassini/>

| color=Orange<ref name=Cassini/>

| albedo=0.21<ref name=ssdphys/>

| albedo=0.21<ref name=ssdphys/>

}}'''Titan''' ([[Greek]] Τῑτάν first-generation god) is the largest [[satellite]] of [[Saturn]], the second-largest planetary satellite in the [[solar system]] (after [[Ganymede]]), and the only body other than [[Earth]] to have bodies of liquid on its surface for any length of time. Titan is twentieth in order from Saturn and the sixth satellite of [[dwarf planet]] size (consistent with its official [[International Astronomical Union|IAU]] catalog designation as "Saturn VI").

}}'''Titan''' ([[Greek]] Τῑτάν first-generation god), or '''Saturn VI''', is the largest [[satellite]] of [[Saturn]], the second-largest planetary satellite in the [[solar system]] (after [[Ganymede]]), and the only body other than [[Earth]] to have bodies of liquid on its surface for any length of time. Until recently most [[Astronomy|astronomers]] believed that Titan was the only celestial body other than [[Earth]] to have a dense atmosphere. Titan is twentieth in order from Saturn and the sixth satellite of [[dwarf planet]] size (consistent with its official [[International Astronomical Union|IAU]] catalog designation as "Saturn VI").

The most exciting finds on Titan to date are the liquid hydrocarbon "seas," containing among them more hydrocarbons than the entire proved reserves of [[oil]] and [[natural gas]] on earth.<ref name=Corsi>Corsi, Jerome R. "[http://www.worldnetdaily.com/index.php?fa=PAGE.view&pageId=56480 New data: Maybe oil isn't from dead dinos]." ''WorldNetDaily'', February 15, 2008. Accessed February 16, 2008.</ref>

The most exciting finds on Titan to date are the liquid hydrocarbon "seas," containing among them more hydrocarbons than the entire proved reserves of [[oil]] and [[natural gas]] on earth.<ref name=Corsi>Corsi, Jerome R. "[http://www.worldnetdaily.com/index.php?fa=PAGE.view&pageId=56480 New data: Maybe oil isn't from dead dinos]." ''WorldNetDaily'', February 15, 2008. Accessed February 16, 2008.</ref>

== Discovery and naming==

== Discovery and naming==

The [[Netherlands|Dutch]] astronomer [[Christiaan Huygens]]<ref name=Huygens1/> first discovered Titan on March 25, 1655. He used a telescope far more refined than the one that [[Galileo Galilei]] had earlier used to discover four of the moons of [[Jupiter]].<ref name=VanHelden>Van Helden, Albert. "[http://www.sil.si.edu/silpublications/dibner-library-lectures/2004-VanHelden/2004_VanHelden.pdf Huygens's Rings, Cassini's Division, & Saturn's Children]." Dibner Library Lecture, October 27, 2004. Accessed February 16, 2008.</ref> This was the first of Saturn's moons to be discovered, so Huygens named the object he found ''Saturni Luna'' ([[Latin]] for "Saturn's moon"). [[Giovanni Domenico Cassini]] and other astronomers would eventually discover eight more moons of Saturn, including at least five inside of Titan. With Cassini's discoveries of the first four of these, Titan's name was changed to "Saturn IV." Titan now bears the catalog designation of "Saturn VI," the identifier that the [[International Astronomical Union]] has now assigned it. Recent deep-space robotic missions have discovered that a total of nineteen moons orbit inside Titan, and another thirty-two outside it.

The [[Netherlands|Dutch]] astronomer [[Christiaan Huygens]]<ref name=Huygens1/> first discovered Titan on March 25, 1655. He used a telescope far more refined than the one that [[Galileo Galilei]] had earlier used to discover four of the moons of [[Jupiter]].<ref name=VanHelden>Van Helden, Albert. "[http://www.sil.si.edu/silpublications/dibner-library-lectures/2004-VanHelden/2004_VanHelden.pdf Huygens's Rings, Cassini's Division, & Saturn's Children]." Dibner Library Lecture, October 27, 2004. Accessed February 16, 2008.</ref> This was the first of Saturn's moons to be discovered, so Huygens named the object he found ''Saturni Luna'' ([[Latin]] for "Saturn's moon"). [[Giovanni Domenico Cassini]] and other astronomers would eventually discover eight more moons of Saturn, including at least five inside of Titan. With Cassini's discoveries of the first four of these, Titan's name was changed to "Saturn IV." Titan now bears the catalog designation of "Saturn VI," the identifier that the [[International Astronomical Union]] has now assigned it. Recent deep-space robotic missions have discovered that a total of nineteen moons orbit inside Titan, and another forty outside it.<ref>The list of Saturn's moons might not yet be complete, and does not include three moons that recent observations have suggested but not yet proved.</ref>

Titan got its common name from [[John Herschel]] (son of the astronomer [[William Herschel]]). He gave Titan a generic name for the [[Titan]]s of mythology, and also named the other seven moons then known after specific deities among the Titans.<ref>Lassell, "[http://adsabs.harvard.edu//full/seri/MNRAS/0008//0000042.000.html Satellites of Saturn]," ''Monthly Notices of the Royal Astronomical Society'', 8:42, November 12, 1847. Accessed February 16, 2008.</ref>

Titan got its common name from [[John Herschel]] (son of the astronomer [[William Herschel]]). He gave Titan a generic name for the [[Titan]]s of mythology, and also named the other seven moons then known after specific deities among the Titans.<ref>Lassell, "[http://adsabs.harvard.edu//full/seri/MNRAS/0008//0000042.000.html Satellites of Saturn]," ''Monthly Notices of the Royal Astronomical Society'', 8:42, November 12, 1847. Accessed February 16, 2008.</ref>

== Orbital and rotational characteristics ==

== Orbital and rotational characteristics ==

Titan follows a slightly eccentric orbit at a mean distance of 1.22 million kilometers from Saturn's center (or rather, the [[barycenter]] of the Saturnian system). Its sidereal month is 15.85 Julian days, as is the length of its sidereal day. Astronomers therefore consider it in [[tidal lock]] with Saturn.

Titan follows a slightly eccentric orbit at a mean distance of 1.22 million kilometers from Saturn's center (or rather, the [[barycenter]] of the Saturnine system). Its sidereal month is 15.85 Julian days, as is the length of its sidereal day. Astronomers therefore consider it in [[tidal lock]] with Saturn.

Titan is also in a 3:4 orbital resonance with the satellite [[Hyperion]], the next farther satellite in the Saturnian system.

Titan is also in a 3:4 orbital resonance with the satellite [[Hyperion]], the next farther satellite in the Saturnian system.

Titan's bulk is probably half water ice and half rock, in several layers with a rock center and several layers of various crystalline forms of ice.<ref name=Arnett/>

Titan's bulk is probably half water ice and half rock, in several layers with a rock center and several layers of various crystalline forms of ice.<ref name=Arnett/>

== Atmosphere ==

== Atmosphere ==

Until 2005, Titan was regarded as the only natural satellite in the [[solar system]] to have a true [[atmosphere]]. But the [[Cassini-Huygens mission]] has already demonstrated that Saturn's inner moon [[Enceladus]] ''also'' has an atmosphere, believed composed of ionized [[water]] vapor from repeated eruptions from [[volcano]]es and/or [[geyser]]s on its surface. This "atmosphere" is constantly escaping from Enceladus, perhaps to persist as the E ring of Saturn's ring system. Thus it requires a continuous source of replenishment. The theories of Enceladus' volcanic and/or geothermal activity are an attempt to explain this replenishment.<ref name=encelatm>"[http://www.esa.int/SPECIALS/Cassini-Huygens/SEM9RC2IU7E_0.html Cassini finds atmosphere on Enceladus]." ''ESA Cassini-Huygens, March 16, 2005. Accessed February 16, 2008.</ref>

Until 2005, Titan was regarded as the only natural satellite in the [[solar system]] to have a true [[atmosphere]]. But the [[Cassini-Huygens mission]] has already demonstrated that Saturn's inner moon [[Enceladus]] ''also'' has an atmosphere, believed composed of ionized [[water]] vapor from repeated eruptions from [[volcano]]es and/or [[geyser]]s on its surface. This "atmosphere" is constantly escaping from Enceladus, perhaps to persist as the E ring of Saturn's ring system. Thus it requires a continuous source of replenishment. The theories of Enceladus' volcanic and/or geothermal activity are an attempt to explain this replenishment.<ref name=encelatm>"[http://www.esa.int/SPECIALS/Cassini-Huygens/SEM9RC2IU7E_0.html Cassini finds atmosphere on Enceladus]." ''ESA Cassini-Huygens, March 16, 2005. Accessed February 16, 2008.</ref>

== The Prebiotic-Abiotic Controversy ==

== The Prebiotic-Abiotic Controversy ==

The Huygens lander has thus far found no biological process, though it has found the suspected constituents, and more. But gas-chromatograph mass spectrophotometric findings have also shown that the bulk of the methane on Titan is actually ¹³C methane--not the ¹²C methane that one would normally expect from biological processes.<ref name=Goddard>"[http://www.spaceref.com/news/viewpr.html?pid=18410 Titan's Mysterious Methane Comes From Inside, Not The Surface]." Press release, [[Goddard Space Flight Center]], [[NASA]], November 30, 2005. Accessed February 16, 2008, from <http://www.spaceref.com/></ref> Scientists at the Goddard Space Flight Center conclude that this methane is vented to the surface from a supply that was somehow trapped deep beneath the surface when Titan was formed. Furthermore, this lends further support to Thomas Gold's 1998 hypothesis that Earth's own supplies of oil and natural gas are in fact abiotic in origin.<ref name=Corsi2>"[http://www.worldnetdaily.com/news/article.asp?ARTICLE_ID=47675 'Fossil fuel' theory takes hit with NASA finding]." ''WorldNetDaily'', December 1, 2005. Accessed February 16, 2008.</ref>

The Huygens lander has thus far found no biological process, though it has found the suspected constituents, and more. But gas-chromatograph mass spectrophotometric findings have also shown that the bulk of the methane on Titan is actually ¹³C methane--not the ¹²C methane that one would normally expect from biological processes.<ref name=Goddard>"[http://www.spaceref.com/news/viewpr.html?pid=18410 Titan's Mysterious Methane Comes From Inside, Not The Surface]." Press release, [[Goddard Space Flight Center]], [[NASA]], November 30, 2005. Accessed February 16, 2008, from <http://www.spaceref.com/></ref> Scientists at the Goddard Space Flight Center conclude that this methane is vented to the surface from a supply that was somehow trapped deep beneath the surface when Titan was formed. Furthermore, this lends further support to Thomas Gold's 1998 hypothesis that Earth's own supplies of oil and natural gas are in fact abiotic in origin.<ref name=Corsi2>"[http://www.worldnetdaily.com/news/article.asp?ARTICLE_ID=47675 'Fossil fuel' theory takes hit with NASA finding]." ''WorldNetDaily'', December 1, 2005. Accessed February 16, 2008.</ref>

This latest finding militates against the speculation that life might exist on Titan. Many scientists believe that Titan's chemistry and physical features are of a type that could have given rise to the earliest chemicals required for [[life]], had Titan been much closer to the [[Sun]] than it actually is. That speculation predates the Cassini-Huygens mission and includes a model suggesting that Titan harbored a vast underground reservoir of [[ammonia]] solution.<ref name=Fortes>Fortes, A. B. "[http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-45FC0TP-26&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=aa73d6642eb13527397bbec9ff9ca535 Exobiological Implications of a Possible Water-Ammonia Ocean Inside Titan]." ''Icarus'', 146(2):444-452, August 2000. Accessed February 16, 2008. [http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WGF-45FC0TP-26-1&_cdi=6821&_user=10&_orig=search&_coverDate=08%2F31%2F2000&_sk=998539997&view=c&wchp=dGLbVlb-zSkWz&md5=644f3640a5d78afc50f8e4e50a4a09d2&ie=/sdarticle.pdf Full text] available to subscribers or for a fee.</ref> That particular model depended on the methane and the cyanide being biogenic, but as has been noted above, the methane certainly is ''not'' biogenic. The ammonia-water "[[aquifer]]" might yet exist, however, if the ⁴⁰Ar findings are a reliable indicator.<ref name=HuygensFindings/>

This latest finding militates against the speculation that life might exist on Titan. Many scientists believe that Titan's chemistry and physical features are of a type that could have given rise to the earliest chemicals required for [[life]], had Titan been much closer to the [[Sun]] than it actually is. That speculation predates the Cassini-Huygens mission and includes a model suggesting that Titan harbored a vast underground reservoir of [[ammonia]] solution.<ref name=Fortes>Fortes, A. B. "[http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-45FC0TP-26&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=aa73d6642eb13527397bbec9ff9ca535 Exobiological Implications of a Possible Water-Ammonia Ocean Inside Titan]." ''Icarus'', 146(2):444-452, August 2000. Accessed February 16, 2008. [http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WGF-45FC0TP-26-1&_cdi=6821&_user=10&_orig=search&_coverDate=08%2F31%2F2000&_sk=998539997&view=c&wchp=dGLbVlb-zSkWz&md5=644f3640a5d78afc50f8e4e50a4a09d2&ie=/sdarticle.pdf Full text] available to subscribers or for a fee.</ref> That particular model depended on the methane and the cyanide being biogenic, but as has been noted above, the methane certainly is ''not'' biogenic.

 

The ammonia-water "[[aquifer]]" might yet exist, however, as a vast subsurface ocean. The ⁴⁰Ar findings certainly suggest this.<ref name=HuygensFindings/> But recently Cassini's controllers carefully mapped fifty of Titan's landmarks and then discovered an apparent shift of all fifty landmarks by as much as 30 km (less than 20 miles). This finding suggests that the moon's crust is somehow decoupled from its core and is floating on top of a liquid layer. Astronomers believe that this layer lies 100 km (over 60 miles) deep to the rocky surface.<ref name=NASANH3>Brown, Dwayne, and Martinez, Carolina. "[http://www.nasa.gov/home/hqnews/2008/mar/HQ_08085_cassini_ocean.html Cassini Spacecraft Finds Ocean May Exist Beneath Titan's Crust]." [[National Aeronautics and Space Administration|NASA]], March 20, 2008. Accessed May 16, 2008.</ref>

 

The most serious problem that Titan poses for [[uniformitarianism|uniformitarian]] theories is that astronomers still have not found the vast reserves of methane that would be necessary to maintain the current level of methane in the atmosphere over [[deep time]]. Lorenz and his colleagues state flatly that Titan must be subject to drastic climate change unless an as-yet unaccounted-for internal source of methane is replenishing the atmosphere ''"at exactly the right rate"'' (emphasis added).<ref name=Lorenz/>

 

== Observation and Exploration ==

== Observation and Exploration ==