A Programme of Research in Planetary and Solar System Science - Understanding the Formation of Phosphorus and Nitrogen Compounds

Phosphorus (P) and Nitrogen (N) are important components of biologically interesting molecules. This consolidated proposal contains two projects; firstly looking at mechanisms of generating bioavailable phosphorus released from meteoric particles in the atmospheres of early Earth, Mars and Venus and secondly examining the incorporation of atomic nitrogen into complex organic molecules relevant for the production of astrobiologically interesting compounds and aerosol particles in Titan's atmosphere (one of Saturn's moons).

Phosphorus and the Inner Planets - The major route to the generation of atmospheric phosphorus is its release as meteoric particles burn up in the upper atmospheres of the inner planets. We seek to characterize this process and to determine the amount of P entering into the atmosphere. Once released elemental P will start to be oxidized by O, OH, O2 and O3. We have identified crucial steps in this oxidation process that can lead to phosphorus compounds, phosphates and phosphites, which have markedly different bioavailability on reaching the planet's surface. We will combine our meteor ablation studies and kinetic data within atmospheric models to determine the relative efficiency of phosphate and phosphite production and estimate the total flux of P to the planet surface. The project links to on-going studies of the Martian atmosphere such as the MAVEN project.

Nitrogen and Titan - Titan is an interesting solar body, like Earth its atmosphere is predominantly nitrogen, N2, but Titan is surrounded by an orange haze comprised of aerosol particles containing complex organic molecules. The exact composition and mechanism of formation of these particles is unknown. For the last 10 years or so, the Cassini mission has been sending back data on Titan (and Saturn) which has stimulated research in a variety of areas.
Nitrogen is generally extremely unreactive in Titan's lower atmosphere, however, in the upper reaches of Titan's atmosphere absorption of high energy radiation and other processes generate N atoms. We will characterize critical reactions in the incorporation of these atomic species into the hydrocarbons that exist in Titan's atmosphere. The HCN molecule lies at the heart of this chemistry, yet there is very poor agreement between measurements and models of this species. We will use our laboratory data (measurements of the rates of these reactions at the cold temperatures and low pressures of Titan's upper atmosphere) and atmospheric models to try and close the gap between measurements and models and to assess the mechanisms by which N is incorporated into Titan's haze layer.

Knowledge Exchange
Plane is deputy director of the new Priestley International Centre for Climate at the University of Leeds: the centre includes comparative planetary climates in its remit and public outreach will be an important part of its mission. In 2013, Plane organised an international meeting at Leeds on the scientific use of sub-orbital reusable vehicles in which XCOR (a US Aerospace company) participated. He is now part of the science team of Project Possum (projectpossum.org), which is involved in training scientist-astronauts for sub-orbital flights (at Embry-Riddle Aeronautical University in Florida). Plane is part of the science team for a THz satellite mission for sounding planetary upper atmospheres (LOCUS), involving RAL Space, Surrey Satellite Technology Ltd, and Star-Dundee. He works with Professor David Jackson (Met Office) as part of the Leeds/Met Office partnership to extend its Unified Model, which is used for weather and climate applications, into the thermosphere for space weather prediction. He and Professor Chipperfield (Earth & Environment, Leeds) have been awarded a Leeds/Met Office case studentship to work in this area.
Seakins an external advisor to a Norwegian project looking at the atmospheric degradation of the nitrogen containing amine compounds that are used in carbon capture and storage. The knowledge gained by Seakins in past studies on amine chemistry and output from the Norwegian project have synergies with the current project; for example, the reactive imine species is common to both amine oxidation in the Earth's atmosphere and HCN formation in Titan's atmosphere. Seakins is a member of the Doctoral Training Centre on Bioenergy led from the School of Chemical Engineering which has links with a number of fuels companies, for example in 2015 Seakins has gave a presentation to Shell on the role of MESMER in combustion modelling. Developments in MESMER including parallelization will enhance capability and further uptake (>200 downloads in 2015). As mentioned in the Overview, knowledge of chemical mechanisms derived for other environments can be very relevant to planetary atmospheres.
Heard operates laser-based field instrumentation designed for ground and aircraft deployment which is a central part of the Atmospheric Measurement Facility of the National Centre for Atmospheric Science. His measurements provide an important validation for the Leeds Master Chemical Mechanism, whose development was funded via DEFRA and used as a policy tool for air quality modelling. He is funded to work with the SME Cambridge Environmental Research Consultants (CERC) to evaluate chemical mechanisms used in urban-scale dispersion modelling in London, and is collaborating with Chinese scientists to understand basic processes controlling gas and aerosol pollution in Beijing.

Outreach
The applicants are all aware of the potential of planetary science to excite and enthuse students of all ages whilst also providing opportunities to present fundamental aspects of chemistry with clear and interesting applications. The applicants regularly give presentations to Schools (e.g. Wrexham 6th Form College, ChemSix Conference, Nottingham - Seakins; Brighton College, Dulwich College, Whitgift School, Franklin School - Heard; Bolton Lecture 2014, Plane). Increased PDRA resource will give us the opportunity to enhance our on-line presence through development of a project website. Heard and his group are involved with the development of educational materials (including videos) in atmospheric chemistry designed for non-experts, similar material will be produced for this project.