Reading: One purpose of this class is to use Titan to review the course content. So, the reading is class notes - Classes 1 to 22.
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Latest images - "backside" - Natural light, 938nm methane window, false color composite
E.g. Table of Titan properties
a=9.5 AU, R=2575 km, g=1.36 m/s2, Vesc=2.6 km/s
P=Po exp -(z/H) where H=kT/mg ~19 km and Po=1.5 Bars
To=95K, <m>=28 amu
Po=no kTo -> no= 10^26 m-3 ( 4 x earth)
rho=no <m> = 5.4 kg m-3 (1.2 x earth)
Mc = rho H = 10^5 kg m-2 (10 x earth)
NOTE: We do not know the Argon abundance - critical for understanding the origin of the atmosphere - nor the isotope abundances....
Altitude Structure - Layers
WHY this profile? Heat budget
Adiabatic lapse rate = g/cp - at the very bottom, where non-adiabatic processes are important
Non-adiabatic processes: latent heat, absorption, radiation, scattering...
If you want to look at the surface at what wavelengths do you look?
Determination of composition comes from high-resolution spectroscopy such as this:
Detection of water in the upper atmosphere - shows water being brought into the upper atmosphere by comets. Similar argument for CO2 and CO.
Solar flux = So / (a in AU)^1/2 - divide by 4 to get average over planet - at Titan F=1368/(4 x 9.5^2)=3.8 W m^-2
Tequilibrium = To (1-A)^1/4 / (a in AU)^1/2 where To= (So/4 sigma)^1/4 = 280K (for So=1368 W m^-2)
Visible Albedo A=0.27 -> Eeq=83K
NOTE: Because of all the scattering there are few shadows - permanently heavily overcast - this is what it looks like:
Methane photochemistry with nitrogen:
Here's the "lite" version:
Latitude distribution - seasonal?
Sources, Losses & Recycling
Source of Titan's atmosphere?
Losses of Titan's atmosphere?
Methane is recycled in a similar way to water in the Earth's atmosphere through the hydrological cycle......
Ideas of how organic raindrops develop and grow as thy slowly drop.....
Fat raindrops (up to centimeter) caused by slow descent.
Dave Grinspoon's version - with biology....
Source of these "warm underground lakes"?
In upper atmosphere UV dissociates CH4
Meteorology / Dynamics
NOTE: Persistent longitudinal variations and significant temporal variations - cloud outburst
Eccentricity of Saturn = 0.056 = 5.6% (compare with Earth = 1.7%).
Looking at the solar flux over the year we see a similar asymmetry that we saw at Mars due to the orbital eccentricity.
Units of Watts m^-2 at outer atmosphere
Here's the picture overview