Revised tholin profile for the atmosphere of Titan

Mao-Chang Liang1, J. A. Kammer, X. Zhang3, D. Shemansky4, Y. L. Yung2

1 Research Center for Environmental Change, Academia Sinica2 Division of Geological and Planetary Sciences, California Institute of Technology

3 University of Arizona4 Space Environment Technologies

Stellar occulations Aerosol extinction profiles Tb Vi, Tb Sco, T21 Eri, T41 CMa (ingress &

egress), T47 Uma Solar occulation

T0 Scattering spectrum at 1040 km

Cassini UVIS

Lorenz + Mitton 2002

Solar Scattering

Stellar Occultation

J. Ajello

T0 olar reflection spectrum

High resolution slit; Integration time 14910 sec; Red line: Effective altitude 1040 km; mid pixel 1203 km Green line: Effective altitude 1612 km Cyan line: best fitting model spectrum

T0 UVIS extinction spectrum

Liang et al. 2007

tholin

CH4

Impact: 514 km

UVIS extinction profiles

Modeling – No production/loss

10-15 g cm-2

76 A

~10-3 g cm-3

eddy

10-2 g cm-310-3 g cm-3

Solution #1 – C2H2 -> tholin

10-15 g cm-2310-15 g cm-2

310-15 g cm-2

size increase76 A -> 3300 A

Extinction coefficient

10 100 10000.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

f(x) = 0.000243496113302863 x^1.42478976157753R² = 0.987634236700597

Particle radius (A)

Fractal particles

Aggregate of molecules at ~1000 km monomer: 10 A Mie radius: 76 A density: ~10-3 g cm-3

-> fractal dimension: ~1.5

Main haze (<300 km) monomer: 66 nm fractional dimension:

2

Low density fractal particle ~10-3 g cm-3 abve ~800 km

Particle size of 76 A at 1040 km Increase to ~3300 A below ~500 km,

compared to 660 A monomer size below 300 km

Mass flux from the top is ~10-15 g cm-2

No net production between 400-800 km

Summary