Titan

Saturn's biggest satellite, 2nd biggest in solar system (behind Ganymede).

Most amazingly, Titan has an atmosphere. A big one. Surface pressure is 1.5 atmospheres!

From Earth, methane was detected spectroscopically. When Voyager 1 flew by, this methane was confirmed, but it was realized that nitrogen (N₂) was the dominant gas in the atmosphere.

Titan's atmosphere:

Nitrogen (N₂) 82-99%
Methane (CH₄) 1-6%
Argon? (Ar) 0-10% (?)
Minor constituents (organic compunds!):

Hydrogen (H₂)
Ethane (C₂H₆)
Propane (C₂H₈)
Ethalyne (C₂H₄)
Hydrogen cyanide (HCN)
Carbon monoxide (CO)

Ultraviolet radiation from the Sun interacts with the methane in the atmosphere to produce the ethane, propane, ethalyne, etc - a photochemical smog. (Where else in the solar system do we have a photochemical smog?)

Titan's surface:

Cold: 94 degrees Kelvin

Triple point: combination of temperature and pressure under which a substance can exist as liquid, solid, and vapor.

Methane temperature triple point: 90.7K (near Titan's surface temperature)
Methane pressure triple point: 117 millibar (a few km up in Titan's atmosphere)

Methane may act on Titan the way water does on the Earth!

methane clouds almost certainly exist
methane/ethane rain? ("raining frozen gasoline")
methane/ethane snow?
methane/ethane lakes and oceans?

Think about this:

Thick atmosphere
Liquid on surface
Organic compounds

What does this sound like?

The Cassini/Huygens Mission

2004/5: Saturn orbiter/Titan lander, provided shots of Titan's surface