Seminar: Cyanides of the Solar System: Spectroscopic studies of Titan’s ices and aerosols (Dr. Courtney Ennis)

Thursday, 21 November 2019 - 12:00pm – Thursday, 21 November 2019 - 1:00pm  |  ChemSci M10

Abstract

The exploration of Saturn’s icy moon Titan by the Cassini-Huygens spacecraft uncovered numerous complex organic molecules. Generated by UV photochemistry and fast particle interactions with methane and molecular nitrogen in the cold upper atmosphere, reactive gas-phase radicals react to form various higher-order cyanides (nitriles). As these cyanide products subside to lower altitudes, they condense and form aerosols. It is these small particles that may play an important role as vehicles transporting organic material to the Titan surface; cargo that potentially includes biomolecules such as amino acids. The search for life’s building blocks will be the focus of a new mission to Titan - NASA’s Dragonfly drone - embarking in 2026.

This talk will focus on the spectroscopic detection and solid-state chemistry of cyanide-type ices; as performed through laboratory simulations of the Titan environment. Although a suite of gas-phase cyanide compounds have already been confirmed in Titan’s atmosphere, the overall molecular composition of cyanide aerosols has been difficult to characterise. This is due to most cyanides displaying similar condensation curves at lower altitudes, leading to the nucleation and growth of composite ices with complicated IR spectra.

Our recent work has used custom built setups at the Australian Synchrotron and at our Otago laboratory to recreate Titan’s aerosol and surface icesystems for characterisation of amorphous, crystalline, and mixed-phase cyanide ices. Combined with periodic-DFT methods to predict solid-state frequencies, we have compiled spectral libraries for the far-infrared identification of target cyanides and developed new laboratory methods to extract physicochemical aerosol properties such as composition, particle size, and morphology.

References:

[1] Ennis, C.; Auchettl, R.; Appadoo, D.R.T. & Robertson E.G. 2017. PCCP, 19, 2915-2925.
[2] Auchettl, R.; Ruzi, M.; Appadoo, D.R.T. & Robertson E.G. & Ennis, C. 2018, ACS Earth & Space Chemistry, 2, 811-820.
[3] Ennis, C.; Auchettl, R.; Appadoo, D.R.T. & Robertson E.G. 2017, MNRAS, 471, 4265-4274.
[4] Ennis, C.; Auchettl, R.; Appadoo, D.R.T. & Robertson E.G. 2018, PCCP, 20, 23593-23605.