Planetary Science at Oxford Physics 2022

This proposal in planetary physics ranges from studying the atmospheres of the 'Ice Giants' giant planets through to studying the reflectance and thermal properties of airless bodies such as asteroids, which are the primary ways in which these bodies can be studied. The programme outlines a coordinated effort to: 1) measure and understand the fluid circulations, cloud condensation and photochemistry in ice giant planet atmospheres, both within the Solar System and beyond; and 2) measure and interpret the spectra of airless planetary bodies to better understand their origins, composition and regolith structure. We have four complementary main projects.

Project 1: The complex, zonally banded atmospheric circulations of all of the giant planets in the Solar System appear to extend over depths that are neither very deep compared to the planetary radius, nor confined solely to a shallow 'weather layer'. This leaves unanswered a host of questions concerning the dynamical origin of their meteorology, the formation and organization of clouds and hazes and the resulting transport of heat and material tracers. In this project, we will test and evaluate possible dynamical mechanisms for energizing the principal features of the atmospheric circulations of the relatively unexplored 'Ice Giant' planets, Uranus and Neptune. Our approach will use a combination of innovative analyses of the observed wind and thermal structure from the Voyager spacecraft, ground-based observations and potentially the JWST, together with a new state-of-the-art global numerical circulation model of the deep weather layers of both planets.

Project 2: Uranus and Neptune, the 'Ice Giants', are of increasing interest due to their relevance to the 'mini-Neptunes' being discovered about other stars and rapidly improving ground-based and space-based telescope observations. However, it remains unclear how clouds form in the atmospheres of these Ice Giants, how their formation is related to the overall overturning atmospheric circulation, and how bright, discrete storm cloud features are linked to atmospheric dynamics and thermal anomalies. In this project we will link near-infrared (near-IR) reflection measurements with thermal-IR emission observations taken contemporaneously to explore cloud formation in hydrogen-rich Solar System Ice Giant Planets and analyse these observations with fundamental modelling. This will ultimately benefit the understanding of clouds in both Solar System planets and exoplanets.

Project 3: Primitive asteroids (usually assumed to be C- and B-type asteroids) hold important clues to the formation and evolution of the Solar System. In this project, enabled by our roles as a Co-Investigator on the mission and members of the sample analysis team, we will use data from NASA's OSIRIS-REx mission to study primitive asteroid Bennu in preparation for measurements of the sample during the grant period. As part of the mission's science team, and using our bespoke laboratory and numerical modelling capabilities, our work will place the returned sample into geologic context and also help determine Bennu's place in the wider context of the Solar System's asteroid populations.

Project 4: Remote sensing measurements in the thermal infrared (TIR) can be used to determine the composition and physical properties of an airless body through spectroscopy and temperature mapping. Surface temperature datasets are being acquired by missions including NASA's Lunar Reconnaissance Orbiter (LRO) and upcoming lunar landers and orbiters, and to interpret them correctly requires new laboratory measurements. This project addresses how thermal emission varies with observation angle, surface roughness and porosity by using and upgrading a unique experimental facility, the Oxford Space Environment Goniometer, to make targeted laboratory measurements to maximise the return from these new and future datasets.