Changes

The atmosphere is not of uniform composition. Clouds, presumably of methane, do form. Furthermore, Huygens' images of the surface show clear signs of erosion and formations that look like dry riverbeds, a sign that rain occurs--though the rain is of methane, not water.<ref name=Arnett/> However, the data do ''not'' indicate the looked-for "ocean" of methane, but rather indicate something akin to the seasonal rivers and lakes seen on earth.<ref name=Arnett/><ref name=HuygensFindings/>

The atmosphere is not of uniform composition. Clouds, presumably of methane, do form. Furthermore, Huygens' images of the surface show clear signs of erosion and formations that look like dry riverbeds, a sign that rain occurs--though the rain is of methane, not water.<ref name=Arnett/> However, the data do ''not'' indicate the looked-for "ocean" of methane, but rather indicate something akin to the seasonal rivers and lakes seen on earth.<ref name=Arnett/><ref name=HuygensFindings/>

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>

[[Image:TitanNorth.jpg|thumb|400px|left|Radar map of Titan's north polar region]]

[[Image:TitanNorth.jpg|thumb|400px|left|Radar map of Titan's north polar region]]

== The Prebiotic-Abiotic Controversy ==

== The Prebiotic-Abiotic Controversy ==

Before the launch of the [[Cassini-Huygens mission]] (see below), speculations on whether Titan had the required elements for [[abiogenesis]] were rife.<ref name=solarviews/> Specifically, scientists believed that the [[methane]] in Titan's atmosphere would combine photochemically to yield [[ethane]], [[ethylene]] (ethene), [[acetylene]] (ethyne), and hydrogen [[cyanide]], and thus form [[amino acid]]s.<ref name=solarviews/><ref name=nasa2/>

Before the launch of the [[Cassini-Huygens Mission]] (see below), speculations on whether Titan had the required elements for [[abiogenesis]] were rife.<ref name=solarviews/> Specifically, scientists believed that the [[methane]] in Titan's atmosphere would combine photochemically to yield [[ethane]], [[ethylene]] (ethene), [[acetylene]] (ethyne), and hydrogen [[cyanide]], and thus form [[amino acid]]s.<ref name=solarviews/><ref name=nasa2/>

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>

In 1994 the [[Hubble Space Telescope]] took photographs of an apparent "continent" on the Saturnian face of Titan.<ref name=nasa2/>

In 1994 the [[Hubble Space Telescope]] took photographs of an apparent "continent" on the Saturnian face of Titan.<ref name=nasa2/>

The first truly comprehensive study of that system is the [[Cassini-Huygens mission]], which launched on October 15, 1997 and arrived in the Saturnian system on July 1, 2004.<ref name=solarviews/> The major innovation of this mission was the use of radar equipment aboard the orbiter and the lander, to penetrate the haze.

The first truly comprehensive study of that system is the [[Cassini-Huygens Mission]], which launched on October 15, 1997 and arrived in the Saturnian system on July 1, 2004.<ref name=solarviews/> The major innovation of this mission was the use of radar equipment aboard the orbiter and the lander, to penetrate the haze.

Huygens was designed to land, and to study the atmosphere and the surface in detail on the way down. Huygens landed fully functional on Titan on January 14, 2005. It remained functional for three hours while it sent back many images and much data on the composition, including the carbon-isotopic ratio, of the Titanian atmosphere.

Huygens was designed to land, and to study the atmosphere and the surface in detail on the way down. Huygens landed fully functional on Titan on January 14, 2005. It remained functional for three hours while it sent back many images and much data on the composition, including the carbon-isotopic ratio, of the Titanian atmosphere.