JWST: A New Voyager for the Outer Solar System

The first 18 months of JWST scientific operations have produced a treasure trove of new discoveries for the four giant planets, whilst challenging the community to develop innovative software tools to deal with untested instruments on a brand-new facility. Spectacular NIRCAM images of all four giants have provided new views of their vigorous weather systems, wispy hazes, and ionospheric emissions, and have enabled the tracking of Jupiter’s atmospheric dynamics at previously unseen altitudes, unravelling three-dimensional structure of Jupiter’s atmospheric circulation.

But the key strength of JWST for giant planet studies are the integral field unit spectrometers, NIRSpec (0.6-5.3 µm) and MIRI/MRS (4.9-28.5 µm). These provide spatially-resolved spectroscopy at high spectral resolution (R~1500-3700) across their fields of view (from 3×3″ for NIRSpec, to a maximum of 6.6×7.7″ at the longest MIRI wavelengths). Uranus and Neptune fit perfectly within these fields-of-view, whereas complex mosaics are needed for Jupiter and Saturn. This presentation will showcase some of the key giant-planet results from the Guaranteed-Time programmes (GTO) and Early-Release (ERS) Jupiter programme during Cycle 1. These include maps of Jupiter’s Great Red Spot and South Polar aurora; observations of Io, Ganymede and the jovian rings; maps of Saturn’s northern summertime hemisphere and rings; observations of Saturn’s smaller satellites in reflected sunlight; and global maps of Uranus and Neptune from the troposphere to the ionosphere.

The latter represent one of the most significant new datasets for Ice Giant science since the days of Voyager-2, and it is hoped that these rich observations will be the start of a long-term programme monitoring the evolving appearance of the giant planets over the lifetime of JWST.