Impacts of Meteoric Material on Earth's Atmosphere: Laboratory studies with Atmospheric Implications

Analogues were developed for Interplanetary Dust Particles (IDPs) and Meteoric Smoke Particles (MSPs). Candidate materials were characterised and compared to the present understanding of the nature of IDPs and MSPs. Knowledge and understanding from meteoritics was used to inform open questions in atmospheric chemistry. The elemental composition, structural, surface and size distribution properties of the candidates was compared to micrometeorites and remote measurements of MSPs. Both relatively rare carbonaceous and the more common ordinary chondritic meteorites and terrestrial minerals were shown to be useful analogues for IDPs, whilst synthetic materials were identified as analogues for MSPs.
Uptake of HNO3 and HO2, based on laboratory experiments, was implemented in a global modelling study. The uptake processes were assessed to determine the region(s) and season(s) in which they would affect atmospheric chemistry. This heterogeneous chemistry augmented previous understanding of gas-phase chemistry, with a view to understanding all sources and sinks of atmospheric species. Whole Atmosphere Community Climate Model (WACCM) runs including uptake were compared to control runs with only gas-phase chemistry. Uptake of both HNO3 and HO2 was shown to alter chemistry in the polar vortex, including effects on many secondary species and feedbacks on each other.
Heterogeneous nucleation kinetics of nitric acid hydrates in Polar Stratospheric Clouds (PSCs) was investigated in the laboratory. SiO2 particles were used as analogues for MSPs processed in acidic solution and the phase which formed was investigated. A newly developed drop freeze assay capable of quantifying heterogeneous nucleation kinetics was used. Nucleation events observed in μl droplets were parameterised using current theoretical models and the results compared to atmospheric observations. The measured heterogeneous nucleation kinetics of the Dihydrate, which then readily converts to the Trihydrate, on SiO2 were shown to be capable of explaining the concentrations of crystals observed in the atmosphere.