Influence of traces elements in the organic chemistry of upper atmosphere of Titan

Abstract : In the upper atmosphere of Titan, complex chemistry leads to the formation of organic aerosols. Since the work of Khare et al. in 1984, several experiments investigated the formation of Titan aerosols, so called tholins, in the laboratory. It has been suggested that nitrogen-containing compounds may contribute significantly to the aerosols formation process. In this study, we focused on the influence of pyridine, the simplest nitrogenous aromatic hydro- carbon, on the chemistry of Titan's atmosphere and on aerosol formation. To assess the effect of pyridine on aerosol formation chemistry, we used two different experimental setups : a capaci- tively coupled radio-frequency (electronic impact), and a VUV Deuterium lamp (photochemistry) in a collaboration between LATMOS (Guyancourt) and NASA-GSFC (Greenbelt), respectively. Aerosols produced with both setups were first analyzed using a FTIR-ATR (Fourier Transform Infrared spectroscopy - Attenuated Total Reflection) with a spectral range of 4000-800 cm−1 to characterize their optical properties. Next the samples were analysed using a Bruker Autoflex Speed MALDI mass spectrometer with a m/z range up to 2000 Da in order to infer their composition. Infrared spectroscopy analysis showed that tholins produced with a nitrogen-methane gas mixture (95:5) and nitrogen- pyridine gas mixture (99:250ppm) present very similar spectra features. Tholins produced with a mixture of nitrogen- methane-pyridine (99:1:250ppm) do not present aliphatic CH2 or CH3 vibrational signatures. This could indicate a cyclic polymerization by a pyridine skeleton. Mass spectrometry is still in progress to confirm this.
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Submitted on : Monday, June 20, 2016 - 10:50:41 AM
Last modification on : Friday, August 2, 2019 - 2:28:01 PM

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  • HAL Id : insu-01333915, version 1

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Christophe Mathé, Nathalie Carrasco, Melissa Grady Trainer, Thomas Gautier, Lisseth Gavilan, et al.. Influence of traces elements in the organic chemistry of upper atmosphere of Titan. Titan Aeronomy and Climate Workshop, Jun 2016, Reims, France. ⟨insu-01333915⟩

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