Exploring the Giant Planet Energy Crisis with JWST

The giant planets, Jupiter, Saturn, Uranus, and Neptune, have always provided a source of both awe and inspiration. Our first close-up glimpses of these systems came from early spacecrafts such as the Pioneers and the Voyagers over 40 years ago, revealing planets that were positively nothing like the Earth. These great spheres of dense gas showed intricate and violent cloud structures, with each planet having more moons than there are planets in the solar system.

The upper atmosphere of these planets contain the interface between the planet and the surrounding space environment, with the charged particle ionosphere being the all important conduit that 'feels' the magnetic field. This is a critical region, because it is here that energy is exchanged via the powerful auroral process, producing stunning displays of light about the magnetic poles. From ground-based observations we can measure the global temperature of the upper atmosphere of the giant planets, and we find that they are much hotter than our models of this region predict. This is a decades-old and a major outstanding question in planetary science and has been dramatically named the 'energy crisis'. Two solutions to this puzzling problem have been proposed. Firstly the aurora can inject significant amounts of energy at the poles, but since these planets are spinning on their axis much faster than the Earth, there are forces that appear to prohibit the movement of this energy down towards the equator. Secondly, the dramatic turbulence that we see in images of theses planets generate waves that can travel up in altitude and break and release their energy in the upper atmosphere, heating it in the process. Up until now, we have not had the high fidelity data needed to test these theories, and to solve this crisis. This is what this Fellowship programme sets out to do.

The James Webb Space Telescope (JWST), a collaboration between American, European, and Canadian space-agencies, is the most powerful telescope ever constructed, and it will be launched from French Guiana on a European rocket in October 2021. Since the telescope is situated in deep space, far away from the Earth's atmosphere, and because the instruments are incredibly sensitive, the facility will provide completely new views of the universe, from our own solar system to the very early universe.

A number of observations have already been planned with JWST, and those include observations of Jupiter and Uranus that I have closely been involved in the development of. These will be unlike anything achievable with telescopes on the ground at Earth, and will provide an incredibly detailed view of the atmospheres of these planets, and an opportunity to once and for all address the energy crisis. This research programme will use two of JWST's instruments - the Mid Infrared Instrument (MIRI), build in the UK with significant involvement by the University of Leicester, and the Near-Infrared Spectrograph (NIRSpec), led by the European Space Agency. By combining data from both instruments, we can capture light from the entire atmosphere, from the deep turbulent base of the atmosphere, all the way up to the upper atmosphere and the ionosphere. The analysis of these data will reveal how energy is transported within and between atmospheric layers, and I will directly test the two proposed solutions to the energy crisis. By observing the atmospheres of both Jupiter and Uranus, we get views of energy transport at both a Gas Giant and an Ice Giant, two different classes of planet that may indeed offer two different solutions to the crisis. Most of the planets discovered outside our solar system share many characteristics with either Jupiter and Uranus, and applying what we learn from this programme can significantly further our understanding of planets orbiting other stars.