What do we know about the chemistry of spacecraft constituent metals in the Lower Mesospehere-Upper Stratosphere?

A large number of low earth orbit satellites are projected in the coming decades, which has led to concerns about environmental impacts of demised spacecraft. The current flux of anthropogenic aluminium vapours entering the Earth’s atmosphere is estimated to be already 10 times larger than the natural flux from meteoroids.
Metals ablated from meteoroids between 80 and 110 km react with atmospheric constituents in the mesosphere forming meteor smoke particles, which are transported by the global circulation to the stratosphere, where they entrain sulfuric acid aerosols and modify their properties. Metals ablated from demised spacecraft at ~60 km have a similar fate: Recent aircraft-based measurements show that 10% of stratospheric aerosols contain metals from re-entering satellites and rocket stages.
In this presentation I will give an overview of what we know about the gas-phase chemistry of spacecraft-relevant metals in the lower mesosphere-stratosphere. Based on this incomplete knowledge, I will speculate about the possible pathways of anthropogenic metals towards stratospheric aerosol and I will highlight uncertainties and experimental/theoretical work that needs to be carried out in order to address them. In particular, I will discuss preliminary results obtained with a modified version of the Meteor Ablation Simulator on the ablation of aluminium particles and the subsequent gas-phase chemistry of aluminium.