Titan tholin properties from
occultation and emission
observations
D. Shemansky, Xi Zhang & Y. Yung
06/26/11
Occultation and emission
measurements are combined to
extract physical properties of aerosols
• The fuv occultation measurements show distinctive continuum
extinction spectra have the shape of the imaginary part of the
Kare et al lab measurements of solid-state tholins in the range
1500 – 1900 A. Vertical profiles extend from 300 km to 1000 km
altitude.
• These results are combined with emission spectra in the fuv that
show the reflection of the solar flux. These observations are
used to extract particle size and abundance using Mie scattering
theory. There are issues with calibration and apparent deviation
from isotropic scattering that need to be resolved.
Figure 7
7
T0_solrfl_radial
TA
los sub solar
T0 long 50
T0 long 25
T0 long -25
TA los subsolar
sub solar = -23o.3
6
sub S/C = -13o.3
10-6 c s-1 cm-2
5
4
T0
3
los S-N
sub solar = -24o.1
sub S/C = -68o.4
2
1
0
-2
-1
0
RT
1
2
Tholin properties
Albedo
1826 A
4.9 x 10-3
Q(Mie)
1826 A
4.9 x 10-3
I(R/A)
1826 A
1.3
Opt depth
1826 A
6.2 x 10-3
Refr index
Tholin
(Kare)
1.65 + 0.235i
r(A)
76
Tholin abnd
(cm-2)
6.9 X 1011
Tholin dens
(cm-3)
3900
Tholin Mixing
ratio
1.2 x 10-6
Issues with observed properties
• Although the revised spectral calibration reduces
the brightness at 1826 A by a factor of about 4,
relative to 1300 A, an isotropic l4 Mie scattering
predicts measureable OI solar line reflection. If
this is caused by wavelength dependent
polarization, a more in-depth analysis is required.
• The flatfield used in the Mos reduction at T0
needs to be reexamined with the new stellar
based flatfield because of significant differences
with the original 2003 LISM based flatfield.