TITAN:-SATURN'S LARGEST MOON

Titan

Saturn's Largest Moon

Size: 5,150 kilometers - Saturn's largest moon - 0.4037 Earths
Orbital radius: 1,221,830 kilometers - 20.3 Saturn radii - outside Saturn's ring system 
Orbital period: 15.945 days
Discovery: 1655 by Christiaan Huygens

Nearly as large as Mars and possessing an atmosphere thicker than Earth's, Titan would categorically be considered a planet if it orbited the Sun on its own.  When scientists first began to understand what that atmosphere was made of -- primarily nitrogen, with a large component of methane and significant quantities of more complex organic molecules -- they quickly realized that Titan would be a place where liquid methane or ethane could be raining from the skies.  Thanks to Cassini-Huygens it is now known that Titan is a youthful planet whose surface is modified and its impact craters erased by the action of flowing liquids and possibly even a methane cycle of cloud formation, rain, runoff, and evaporation, akin to Earth's water cycle. The world revealed to Huygens' cameras as it descended to Titan's surface on January 14, 2005 contains clear signs of river vallies and water-rounded rocks. And Cassini's Titan RADAR mapper is obtaining detailed views of channels and valleys, eroded impact craters, and windblown sand dunes that all speak of Titan's active geology.

The surface of Titan has historically been difficult to explore because the thick hazes of complex hydrocarbons that make its atmosphere so interesting also prevent a clear view to its surface.  Titan stands out for how deep its atmosphere is, with layer upon layer of hazes making for a complicated series of obstacles to the sight of orbiting instruments. Its highest hazes may be 300 kilometers (190 miles) above the ground, nearly four times higher than the highest clouds on any other planet. And these thick hazes are made of piles of different compounds, a "witch's brew" of carbon, nitrogen, and hydrogen compounds.

The Voyager cameras were unable to penetrate Titan's hazes, returning picture after maddening picture of a nearly featureless upper atmosphere. Cassini-Huygens was sent to Titan with cameras capable of piercing spectral "windows" in the haze, a RADAR mapping instrument designed specifically to produce maps of Titan's surface, and the Huygens probe, which was dedicated to the study of Titan's atmosphere.  Despite the quantity of data that has been return so far, Titan still presents many enigmas to scientists.  The complex interrelationships between its atmosphere, its surface, and its interior will take lifetimes to untangle.

	Earth	Titan
Average surface temperature	290 K 15 C 60 F	-90 K -180 C -290 F
Average surface pressure	1 bar	1.6 bars
Major gases	77% Nitrogen 21% Oxygen 0.93% Argon ~ 1% water (varies)	90-97% Nitrogen 0-6% Argon 2-5 % Methane 0.2% Hydrogen
Minor gases (ppm = parts per million)	330 ppm carbon dioxide 18 ppm neon 5.2 ppm helium 1.5 ppm methane 1.1 ppm krypton 0.5 ppm hydrogen 0.4 ppm ozone 0.3 ppm nitrous oxide 0.12 ppm carbon monoxide 0.087 ppm xenon 0.01 ppm ammonia	~45 ppm carbon monoxide ~10 ppm ethane ~2 ppm acetylene ~0.5 ppm propane ~0.2 ppm hydrogen cyanide ~0.1 ppm ethylene ~0.01 ppm carbon dioxide ~0.008 ppm water (at high altitude) ~0.005 ppm acetonitrile ~0.005 ppm cyanogen
Cloud layers: altitude and composition	12-30 km Concentrated Sulfuric Acid, everywhere but transparent 0-12 km Sulfates, dust, sea salt, organic compounds, here and there, may be transparent or opaque 0-12 km Water clouds and fog, making on average 50% opaque cloud cover	200-300 km, variable detached haze layers 35-200 km, variable photochemical haze layer made of carbon-nitrogen-hydrogen polymeric compounds 10-15 km methane liquid and ice clouds, about 10% cloud cover

Only one feature on Titan was famous on Earth-based telescopic observations to be named prior to Cassini's arrival: Xanadu, a large bright-colored splotch on Titan's leading hemisphere.  Now that Cassini has arrived, Titan has earned a complex naming scheme for its wide variety of features:

• Albedo features (large areas that are bright or dark) are named for sacred or enchanted places, paradise, or celestial realms from all the world's cultures.
• Craters and ringed features are named for wisdom deities.
• Facula (small, bright features) are named for islands on Earth that are not politically independent.  Faculae (chains of bright features) are named for Earth archipelagos.
• Flumina (linear, channel-like features) are named for mythical or imaginary rivers.
• Lacus (small, dark features) are named for lakes on Earth.  An attempt is made to find an Earth lake with similar shape to the Titanian lacus.
• Virgae (streaks or stripes of color) are named for rain deities.
• Other features are named for deities of happiness, peace, and harmony from all the world's cultures.

Flyby	Date	Orbit	Flyby geometry	Closest approach altitude	RADAR images?
T0	Jul 02, 2004	Rev 00	Outbound	339,120 km
TA	Oct 26, 2004	Rev 0A	Inbound	1,174 km	yes
TB	Dec 13, 2004	Rev 0B	Inbound	1,192 km
TC	Jan 14, 2005	Rev 0C	Inbound	60,003 km
	-- Huygens mission --
T3	Feb 15, 2005	Rev 03	Inbound	1,579 km	yes
T4	Mar 31, 2005	Rev 05	Outbound	2,404 km
T5	Apr 16, 2005	Rev 06	Outbound	1,026 km
T6	Aug 22, 2005	Rev 13	Outbound	3,669 km
T7	Sep 07, 2005	Rev 14	Outbound	1,075 km	yes
T8	Oct 28, 2005	Rev 17	Inbound	1,353 km	yes
T9	Dec 26, 2005	Rev 19	Outbound	10,409 km
T10	Jan 15, 2006	Rev 20	Inbound	2,043 km
T11	Feb 27, 2006	Rev 21	Outbound	1,813 km
T12	Mar 19, 2006	Rev 22	Inbound	1,951 km
T13	Apr 30, 2006	Rev 23	Outbound	1,855 km	yes
T14	May 20, 2006	Rev 24	Inbound	1,879 km
T15	Jul 02, 2006	Rev 25	Outbound	1,906 km
T16	Jul 22, 2006	Rev 26	Inbound	950 km
T17	Sep 07, 2006	Rev 28	Inbound	950 km
T18	Sep 23, 2006	Rev 29	Inbound	950 km
T19	Oct 09, 2006	Rev 30	Inbound	950 km
T20	Oct 25, 2006	Rev 31	Inbound	950 km
T21	Dec 12, 2006	Rev 35	Inbound	950 km
T22	Dec 28, 2006	Rev 36	Inbound	1,500 km
T23	Jan 13, 2007	Rev 37	Inbound	950 km
T24	Jan 29, 2007	Rev 38	Inbound	2,726 km
T25	Feb 22, 2007	Rev 39	Outbound	950 km
T26	Mar 10, 2007	Rev 40	Outbound	950 km
T27	Mar 26, 2007	Rev 41	Outbound	950 km
T28	Apr 10, 2007	Rev 42	Outbound	950 km
T29	Apr 26, 2007	Rev 43	Outbound	950 km
T30	May 12, 2007	Rev 44	Outbound	950 km
T31	May 28, 2007	Rev 45	Outbound	2,426 km
T32	Jun 13, 2007	Rev 46	Outbound	950 km
T33	Jun 29, 2007	Rev 47	Outbound	1,944 km
T34	Jul 19, 2007	Rev 48	Inbound	1,300 km
T35	Aug 31, 2007	Rev 49	Outbound	3,212 km
T36	Oct 02, 2007	Rev 50	Outbound	950 km
T37	Nov 19, 2007	Rev 52	Outbound	950 km
T38	Dec 05, 2007	Rev 53	Outbound	1,300 km
T39	Dec 20, 2007	Rev 54	Outbound	950 km
T40	Jan 05, 2008	Rev 55	Outbound	950 km
T41	Feb 22, 2008	Rev 59	Outbound	950 km
T42	Mar 25, 2008	Rev 62	Outbound	950 km
T43	May 12, 2008	Rev 67	Outbound	950 km
T44	May 28, 2008	Rev 69	Outbound	1,348 km
T45	Jul 31, 2008	Rev 78	Outbound	3,980 km