The Great Cold Spot in Jupiter's upper atmosphere

Past observations and modelling of Jupiter’s thermosphere have, due to their limited resolution, suggested that heat generated by the aurora near the poles results in a smooth thermal gradient away from these aurora, indicating a quiescent and diffuse flow of energy within the sub-auroral thermosphere. Here, we discuss VLT-CRIRES observations that reveal a small-scale localised cooling of ~200 K within the non-auroral thermosphere. Using IRTF-NSFCam images, this feature is revealed to be quasi-stable over at least a 15-year period, fixed in magnetic latitude and longitude. The size and shape of this “Great Cold Spot” vary significantly with time, strongly suggesting that it is produced by an aurorally-generated weather system: the first direct evidence of a long-term thermospheric vortex in the solar system. We discuss the implications of this spot, comparing it with short-term temperature and density variations at Earth.