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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - GIANTCLIMES (Giants through Time: Towards a Comprehensive Giant Planet Climatology)

Teaser

Summary

Planetary science stands at a unique threshold â€“ the discovery of thousands of new worlds beyond the confines of our own Solar System is bringing a fascinating new perspective on the forces shaping both the architecture of our planetary system and the fragile climate of our home planet. As exoplanetary studies move from a discovery phase into an era of atmospheric characterisation, our own solar system offers an extreme test of our understanding of how planetary climate, dynamics and chemistry differ from world to world, and whets our appetite for the myriad possibilities that remain to be discovered. The next five years will likely be transformational in our understanding of outer solar system environments and the role of giant planet formation on planetary system evolution, with the culmination of the Juno mission at Jupiter and the Cassini mission at Saturn, along with new exploration of Uranus and Neptune by the James Webb Space Telescope (JWST).

But these missions offer only fleeting glimpses of these dynamic, ever-changing worlds when compared to their long orbital periods (10 years for Jupiter, 165 years for Neptune). How does the climate, circulation and chemistry of these atmospheres evolve over these large spans of time? What are the natural cycles of climate variability, and how do they differ from world to world? What can the giant planets reveal about the governing forces shaping planetary atmospheres in all their guises? The aim of GIANTCLIMES is to assemble the first comprehensive climatology of all four giant planets by combining an unprecedented multi-decade archive of ground-based infrared imaging with new spectroscopic observations from space telescopes and visiting spacecraft. This wealth of observational data will be studied via a sophisticated suite of spectral analysis software to understand the spatial and temporal variability in the redistribution of energy and material on the four giants. The GIANTCLIMES programme at the University of Leicester consists of three objectives will provide something that no single space mission has ever done before: the ability to explore the giants over large spans of time.

1. Climate Cycles on Jupiter: What drives the spectacular transformations of Jupiterâ€™s banded structure and triggers storms? Can these events be predicted? We are searching for natural atmospheric cycles on this archetypal giant by constructing a comprehensive climate record (temperature, composition, clouds) over three Jovian years to set the environmental context for short-lived spacecraft missions (e.g., Juno).

2. Gas Giant Stratospheres: How does the circulation and chemistry of planetary stratospheres change with time as a result of the different conditions on each world? We are exploring the changing stratospheres of seasonal Saturn and non-seasonal Jupiter over long timescales to develop a new paradigm for the processes shaping these poorly-understood atmospheric regimes.

3. Ice Giants: How do circulation patterns and climate cycles differ between the Ice and GasGiants? We are combining state-of-the-art observations from space observatories (Spitzer, Herschel, and JWST) to reveal the climate of these distant worlds like never before, providing the first 3D maps of temperature, composition and circulation within an ice giant atmosphere.

Work performed

Theme 1: Jupiter\'s Climate Variability
* Recent publications have explored the moist convective plumes responsible for the revival of Jupiter\'s South Equatorial Belt in 2009-2011 (http://dx.doi.org/10.1016/j.icarus.2017.01.001), the 3-5 year cycle of expansion activity within Jupiter\'s North Equatorial Belt (http://dx.doi.org/10.1002/2017GL073383), and a review of cyclic activity across all of Jupiter\'s main belts (http://dx.doi.org/10.1002/2017GL073806).
* Dr. Arrate Antunano-Martin arrived in Leicester in October 2017 and is working with an infrared dataset spanning more than three jovian years (1983-2018) to identify periodicities and their underlying causes in the jovian atmosphere. The first of several papers on this topic has been submitted for publication (July 2018).
* Dr. Henrik Melin (ERC Collaborator) published a study using the TEXES spectrometer on NASA\'s Infrared Telescope Facility, expanding on our previous work mapping Jupiter\'s temperatures, clouds and composition on a single date (http://dx.doi.org/10.1016/j.icarus.2016.06.008) to understand the variations of stratospheric hydrocarbons over half a jovian year (https://doi.org/10.1016/j.icarus.2017.12.041). This same instrument was used by Dr. Richard Cosentino (Collaborator at Goddard Spaceflight Center) to understand Jupiter\'s Quasi-Quadrennial Oscillation (https://dx.doi.org/10.1002/2017JE005342); by Dr. James Sinclair (Collaborator at the Jet Propulsion Laboratory) to explore the upper atmospheric heating from Jupiter\'s powerful auroras (https://doi.org/10.1016/j.icarus.2017.09.016); and by Doriann Blain (Paris Observatory) to map Jupiter\'s tropospheric ammonia (https://doi.org/10.1016/j.icarus.2018.06.002). Our ERC-funded programme of TEXES observations continues to be awarded time on the IRTF.
* Dr. Leigh Fletcher and Mr. Padraig Donnelly (ERC Collaborator) have continued to support Juno\'s close flybys of Jupiter using the Very Large Telescope in Chile, including a successful visitor-mode run in May 2018 that coincided perfectly with Juno\'s 13th perijove. High-resolution thermal maps of Jupiter will be presented at upcoming conferences, and we are continuing our campaign of Earth-based support for the Juno mission.
* Dr. Fletcher co-organised (with Dr. John Rogers of the British Astronomical Association) a Europlanet-funded workshop at the Royal Astronomical Society in London to bring together members of the Juno team with professional and amateur astronomers exploring atmospheric variability on Jupiter.
* Guaranteed-time observations of Jupiter\'s Great Red Spot (programme ID 1246) using the James Webb Space Telescope (JWST) have been awarded and prepared for execution in the first year of operations.

Theme 2: Saturn\'s Seasonal Stratosphere
* The Cassini mission came to an end in September 2017, and the ERC team at Leicester were involved in a number of media activities associated with the end of mission. Two publications have been prepared by Dr. Fletcher that deal with Cassini infrared spectroscopy spanning the entire mission, 2004 to 2017: the first (published in Nature Astronomy) investigates the evolution of Saturn\'s tropical oscillations in the equatorial stratosphere, and the substantial perturbation caused by the Great Northern Storm of 2010-2013 (http://dx.doi.org/10.1038/s41550-017-0271-5); the second looks at the changes occurring in the polar regions as Saturn\'s northern summer approached (submitted). In addition, Dr. Richard Achterberg (Collaborator) has used the high-resolution infrared observations from Cassini\'s final orbits to understand the properties of Saturn\'s polar cyclones (https://doi.org/10.1029/2018GL078157); and Dr. Sandrine Guerlet (Collaborator) used Cassini observations of Saturn\'s limb to further understand the equatorial oscillations (https://dx.doi.org/10.1002/2017JE005419).
* Dr. James Blake joined the Leicester team in March 2018, and is focussing on exploiting two sources of ground-based observations of Satu

Final results

The above report represents the current status of work in July 2018, 15 months after the start of the grant and 10 months after the arrival of the first PDRA.