Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 – 23 September 2022
Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 September – 23 September 2022
EPSC Abstracts
Vol. 16, EPSC2022-1199, 2022, updated on 14 May 2024
https://doi.org/10.5194/epsc2022-1199
Europlanet Science Congress 2022
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

First Optical Constants from 0.4 to 1.6 µm of Titan Aerosol Analogs Produced in the NASA Ames COSmIC Facility and Their Use in a New Analysis of Cassini VIMS Observations

Ella Sciamma-O'Brien1, Ted Roush1, Pascal Rannou2, and Farid Salama1
Ella Sciamma-O'Brien et al.
  • 1NASA ARC, Space Science and Astrobiology Division, Moffett Field, CA 94087, USA (ella.m.sciammaobrien@nasa.gov)
  • 2Université de Reims Champagne-Ardenne, 51687 Reims, France

We have determined the real and imaginary refractive indices (n and k, respectively), from the visible to the near infrared (0.4 to 1.6 µm), of five laboratory-generated organic refractory materials produced from gas-phase chemistry with the NASA Ames COSmIC facility. The solid samples were produced using a plasma discharge in the stream of a 200-K supersonic jet-cooled expansion of different gas mixtures to study the impact of the molecular precursors on the solid sample optical properties. Three samples were produced from N2:CH4 (95:5) gas mixtures using three different high voltages (700V, 800V and 1000V) to vary the energy in the plasma discharge. One sample was produced from a N2:CH4:C2H2 (94:5:5:0.5) gas mixture, with a high voltage of 1000 V. The fifth sample was produced in an Ar:CH4 (95:5) gas mixture with a high voltage of 1000 V to produce a nitrogen-free hydrocarbon sample. The optical constants, n and k, of these five samples were determined using spectral reflectance measurements. They appear to be positively correlated with the nitrogen content in the solid sample, i.e., a sample with larger nitrogen content exhibits higher n and k values.

We have used these refractive indices as input parameters in a radiative transfer model to analyze Cassini Visible Infrared Mapping Spectrometer (VIMS) observations of Titan’s atmosphere. The results show that using the tholin samples with higher n and k values (higher nitrogen content) provides a better fit to the observational data than using the samples with lower n and k values (lower nitrogen content). The Titan tholins with higher nitrogen content therefore appear to be more representative of the Titan aerosols observed by VIMS.

How to cite: Sciamma-O'Brien, E., Roush, T., Rannou, P., and Salama, F.: First Optical Constants from 0.4 to 1.6 µm of Titan Aerosol Analogs Produced in the NASA Ames COSmIC Facility and Their Use in a New Analysis of Cassini VIMS Observations, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1199, https://doi.org/10.5194/epsc2022-1199, 2022.

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