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Complex organic matter in Titan's atmospheric aerosols from in situ pyrolysis and analysis

Abstract

Aerosols in Titan's atmosphere play an important role in determining its thermal structure1,2,3. They also serve as sinks for organic vapours4 and can act as condensation nuclei for the formation of clouds5,6, where the condensation efficiency will depend on the chemical composition of the aerosols5,7. So far, however, no direct information has been available on the chemical composition of these particles. Here we report an in situ chemical analysis of Titan's aerosols by pyrolysis at 600 °C. Ammonia (NH3) and hydrogen cyanide (HCN) have been identified as the main pyrolysis products. This clearly shows that the aerosol particles include a solid organic refractory core. NH3 and HCN are gaseous chemical fingerprints of the complex organics that constitute this core, and their presence demonstrates that carbon and nitrogen are in the aerosols.

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Figure 1: Signal resulting from the mass spectrometry (MS) analysis of the gases evolved from pyrolysis of the first aerosol sample.
Figure 2: Signal resulting from the MS analysis of the gases evolved from pyrolysis of the second aerosol sample.
Figure 3: Temporal evolution of the intensity of the MS signatures attributed to ammonia for the second aerosol sample pyrolysis.

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Acknowledgements

We acknowledge financial support from CNES, CNRS, the Austrian Ministry of Research and NASA. For the fabrication and qualification of ACP's mechanical and pneumatic components, the prime industrial contractor was SNECMA, and we acknowledge CNES Toulouse who strongly supported the CNRS ACP team. In particular, we thank C. Gelas, R. Salomé and E. Condé. We also thank the other main contractors, The Joanneum Research Institute and Austrian Aerospace, for the quality of their work. We acknowledge the support of the following people during the development of the instrument: M.-C. Gazeau and the LISA team at Créteil, R. Sablé and the ONERA/CERT in Toulouse, C. Cordelle and F. Marchandise at SNECMA, and G. Zeynard at Austrian Aerospace. We are also much indebted to the ESA Huygens Project Team for its constant support.

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Israël, G., Szopa, C., Raulin, F. et al. Complex organic matter in Titan's atmospheric aerosols from in situ pyrolysis and analysis. Nature 438, 796–799 (2005). https://doi.org/10.1038/nature04349

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