Mid-Infrared Observations of the Ice Giants: Recent Discoveries and Future Opportunities with VLT-VISIR and JWST

In this talk, we present highlights from recent and ongoing analyses of mid-infrared observations of Uranus and Neptune.

Drawing from a combination of archival and recent imaging and spectroscopy, we examine the spatial structure and trends of mid-infrared emission from the ice giant atmospheres. We report on surprising temporal variability in the atmosphere of Neptune with an unexpected decline in stratospheric temperatures since at least 2003. Recent VLT-VISIR imaging and spectroscopy are presented, revealing how this trend has progressed.

In contrast, we show that no evidence yet exists of long-term thermal changes in Uranus’ stratosphere, but mid-IR observations of Uranus are still extremely limited. The observed spatial structure of Uranus’ mid-infrared emission is, however, intriguing, as it is inconsistent with simple models of the atmospheric circulation and chemistry, and open to multiple physical interpretations. We share recent observations from VLT-VISIR and express the need for continued ground-based imaging for both Uranus and Neptune.

Finally, we discuss how the James Webb Space Telescope MIRI observations can help greatly advance our understanding of the ice giants, now and in the years ahead. In particular, given its supreme sensitivity compared to ground-based observations, JWST-MIRI observations can resolve the nature of Uranus stratospheric thermal/chemical structure and reveal precisely how temperature and chemical abundances vary over time in the atmospheres of both ice giants.