Thermal Structure and Composition of Jupiter’s Great 2 Red Spot from JWST/MIRI

JWST/MIRI’s MRS mode, utilising 4 IFUs (4.9 – 27.9 μm) observed Jupiter’s Great Red Spot (GRS) in July and August 2022, tracking the horizontal and vertical distributions of temperature, aerosol and compositional gradients across the vortex on timescales longer than the GRS rotation rate of 4 days. This is one of the brightest targets observed by MIRI and algorithms were successfully used to address the challenges of wavelength calibration, desaturation, removal of spatial artefacts as well as navigating this dataset. Retrievals from the 7.30 – 10.75 μm range, presented alongside a suite of supporting visual and near-infrared observations were used to map the distributions of temperature, ammonia, phosphine and aerosols. A series of stratospheric hot-spots were discovered to be co-moving with the longitudinal drift of the GRS, potentially the consequence of atmospheric perturbations propagating upwards into the stratosphere. Both temperature and ammonia distributions within the GRS consistently displayed north-south asymmetries, most likely the result of the GRS tilting in the zonal direction. Ammonia was shown to be depleted above the GRS, indicating that it may be forced to condense due to the low temperature anomaly within the vortex. Meanwhile, the phosphine distribution within the GRS was shown to be proportional to integrated aerosol opacity, suggesting that the excess aerosol layers above the GRS may play a role in maintaining the phosphine population above the GRS by providing shielding from the UV light that would normally photolyse and remove this molecule. A small storm was captured north-west of the GRS in August that also displayed a phosphine excess. This would be a suitable location to search for deep molecular species in future studies. Finally, thermal wind and Brunt-Va¨is¨ala¨ frequency within the GRS is mapped in the vertical direction in unprecedented detail, indicating consistency with the despinning of the anticyclonic winds with altitude and suggesting revised depths for the location of the cloud-tracked winds in the visible for Hubble and the near-infrared for NIRCam.