A Consolidated Grant Proposal for Solar and Planetary Science at the University of Leicester, 2022 - 2025

We propose a world-class programme of research that focuses on 3 main areas of study concerned with our solar system. The first involves study of the outer environments of the planets where the gas is ionised, such that it not only feels the gravitational pull of the planet, but also interacts strongly with its magnetic and electric fields. In the second area we seek to study the origin and evolution of solar system bodies, through examination of materials from asteroid, chondrite and lunar samples, and through laboratory-based exploration of X-ray fluorescence from Mercury analogues. The third area will employ spectroscopy from the James Webb Space Telescope (JWST) and ground observatories to explore the planetary stratospheres and tropospheres at the ice giants Uranus and Neptune.

Previous work in the first area shows that the outer environments of the planets vary widely, determined by the interaction with the plasma that blows continuously from the Sun on the outside, and the interaction with the planet and its moons on the inside. The solar wind is prone to outbursts that can lead to magnetic storms and bright auroras at Earth, as well as varying strongly over the solar cycle, and with distance from the Sun. Its interaction with the planets then depends on whether the planet is magnetised, has an atmosphere, and has active moons. We will use MESSENGER data to study Mercury close to the Sun, a planet that has a magnetic field but almost no atmosphere; use the constellation of spacecraft at Mars, more distant from the Sun, which has an atmosphere but no strong magnetic field to prevent its erosion by the solar wind; and combine multi-spacecraft and ground instrumentation at Earth, at intermediate distances having both an atmosphere and a magnetic field. We will also study the strongly magnetized giant planets Jupiter and Saturn using data from the Juno mission at Jupiter and Cassini at Saturn, combined with observations of the auroras at ultraviolet wavelengths using the Hubble Space Telescope and at infrared wavelengths using large ground-based telescopes. Auroras are caused by large-scale electric currents flowing between the outer environments and the upper ionized atmospheres, which communicate force between these regions. Overall emphasis will be on the complex physical processes that couple the solar wind on the outside, the magnetic field surrounding the planet (if any), and the planetary atmospheres or surface on the inside.

In the second area, laboratory studies, we will analyse material returned from C-class asteroid Ryugu by the Hayabusa2 mission. We will make complementary analyses on Apollo lunar regolith grains and recent, unique carbonaceous chondrite falls to build a new understanding of space weathering and C-class asteroid parent body processes. This project builds on the leading expertise we have in the microanalysis of planetary materials, through electron microscopy at ePSIC and UoL, and synchrotron-based X-ray spectroscopy. Laboratory work focused on Mercury will centre on the MIXS Ground Reference Facility, a purpose-built system to allow detailed analysis of X-ray fluorescence, induced using an X-ray or electron source, for bespoke surface analogues. This laboratory facility will uniquely allow us to expand our science programme using the MIXS data from the BepiColombo mission, both in relation to the dayside surface composition goals at global and local scales on Mercury, and in terms of the nightside magnetosphere-surface interaction which produces a significant X-ray fluorescence associated with electron bombardment.

The final theme leverages Leicester's leadership of the guaranteed-time giant planets programme on the JWST, exploiting MIRI spectroscopic maps of the Ice Giants Uranus and Neptune, combined with a ground-based observation programme, to understand how stratospheric circulation, photochemistry, and tropospheric meteorology shape the atmospheres of sub-giant-sized worlds.