Saturn's Moon Titan
- Like Jupiter's Moon Ganymede, Saturn's satellite Titan is larger than the planet
- Titan is the only moon in the solar system which holds on to
a thick atmosphere.
- Titan's surface gravity is weak (about 1/7 Earth gravity or just a little less than the Earth's Moon), but temperatures are very low (95K or -290F) permitting it to hold on to a significant atmosphere.
- The atmospheric pressure near Titan's surface is 1.5 times
that of Earth.
- As on Earth, the most abundant gas in Titan's atmosphere is nitrogen.
- Methane is the second most abundant gas, amounting to a few percent of the atmosphere.
- Like Earth's atmosphere, Titan's atmosphere has evolved substantially.
- Titan probably originally outgassed an atmosphere of
ammonia (NH3) and methane (CH4).
- Ultraviolet sunlight breaks up ammonia molecules leaving
the nitrogen when the hydrogen escapes.
- Ultraviolet light also drives chemistry which turns
the methane into more complex organics like ethane and other
- A thick photochemical haze (smog) high in Titan's atmosphere
completely hides Titan's surface at visible wavelengths.
- Detailed images of the surface have been made using infrared light (and radar) which better penetrates the small particles.
- Titan's surface shows a strong contrast between bright surface features (high clean ice?) and dark low regions (hydrocarbon sludge/seas?).
- Radar observations from Earth detect glints from Titan which are characteristic of flat smooth surfaces (lakes?).
- Titan may have weather which resembles Earth's.
- Methane (CH4) and Ethane (C2H6)
are trace gasses which may play a role similar to water on the Earth.
- Calculations show that methane condenses to form clouds and may fall as rain (although
it probably evaporates before reaching the surface).
- Ethane falls as a mist and may form puddles or seas or oceans on the surface.
- Indeed, the highest resolution images obtained of Titan's surface (from the Huygen's probe) reveal a surface with landforms resembling terrestrial drainage channels and coastlines.
- The lack of craters suggests active erosion. The existence of surface relief in the presence of erosion suggests a geologically active body
which is constantly building new landforms (ice tectonism/volcanism???).
- Particles bearing complex molecules settle out of the atmosphere
and collect on the surface.
- The surface of Titan may have accumulated several
meters of organic "goo".
- This environment may hold clues to the conditions that
fostered the development of life on Earth.
- Despite a strong greenhouse effect,
the surface temperature of Titan, however, is only about
100oK (about -300oF).
- The temperature is too low for active chemistry to occur.
- But at least what is there is stored in a deep freeze
for our examination.
- However, the existence of (cryo)volcanic features suggests
that warmer conditions (and possibly liquid water) exist below
- Titan is just the largest of dozens of icy satellites of Saturn.
Many of which have their own interesting geological story to tell.
Revised April 27, 2005