Skip to main content
SearchLoginLogin or Signup

New Optical Constants of Titan and Pluto Aerosol Analogs from the Visible to the Infrared and Their Use to Analyze Cassini and New Horizons Observations

Presentation #220.01 in the session Laboratory Investigations (Poster + Lightning Talk)

Published onOct 23, 2023
New Optical Constants of Titan and Pluto Aerosol Analogs from the Visible to the Infrared and Their Use to Analyze Cassini and New Horizons Observations

In planetary atmospheres like those of Titan and Pluto, complex organic solid particles are produced from photolysis and radiolysis processes. These aerosols form haze layers, and also settle to the surface. Their presence can significantly impact the atmospheric and surface spectra obtained by remote-sensing instruments like the Visible Infrared Mapping Spectrometer and Composite Infrared Spectrometer on Cassini and the Ralph instrument on New Horizons. Numerous laboratory experiments have been developed to simulate and investigate the chemistry occurring in Titan’s and more recently Pluto’s atmosphere, resulting in the formation of these solid particles. Many different analytical diagnostics have been used to characterize laboratory-generated analogs (or tholins) of Titan and Pluto aerosols and provide insight on their formation pathways and physical, chemical, and spectral properties. In particular, the complex refractive indices (n + ik, or optical constants) of a variety of Titan and Pluto tholins have been measured over the years.

These optical constants describe how the tholins interact with light (transmission, reflection, absorption, scattering), and are therefore fundamental input parameters to simulate haze particles in radiative transfer models used for the interpretation of observational data. These radiative transfer models can leverage the optical constants of different tholins to explore a wide range of compositions, allowing for improved fits and interpretations of observational data resulting in a better understanding of Titan’s and Pluto’s atmosphere and surface compositions.

Here we present the results of several optical constants studies:

1. The measurements of optical constants of Titan tholins produced from plasma chemistry in N2:CH4-based gas mixtures in the NASA Ames COSmIC Facility from the Visible to the Near Infrared (0.4–1.6 µm) and their use in a new analysis of Cassini VIMS observations[1].

2. The measurements of optical constants of Pluto tholins produced in N2:CH4:CO gas mixtures in COSmIC from 0.4 to 1.6 µm and their use in a new analysis of New Horizons Ralph observations[2,3].

3. The preliminary results of a comparative analysis of two Titan tholin samples produced from plasma chemistry in N2:CH4 gas mixtures in two different experimental facilities: the LATMOS PAMPRE experiment and the NASA Ames COSmIC facility, and measured from 0.4 to 300 µm[4].

References:

[1] Sciamma-O’Brien, E., et al. 2023; PSJ (in press).

[2] Emran, A., et al. (2023) 54th LPSC.

[3] Cook, J. C., et al. (2023) 54th LPSC.

[4] Drant, T., et al. 2023; A&A (submitted).

Comments
0
comment
No comments here