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The Cassini mission has led to many recent results about ocean worlds and what may become a new paradigm for understanding orbital evolution with tidal heating, the model of resonance locking in the parent planet (Fuller et al., 2016). However, there remain fundamental gaps in our understanding of tidal heating and coupled orbital evolution, which motivated a Keck Institute for Space Studies (KISS) workshop on this topic. Tidal heating is key to the evolution and habitability of many worlds across our solar system and beyond. The spectra, in particular the elevated wing of the emission band near 1.69 μm, and their spatial distribution strongly suggest the presence of nonlocal thermodynamic equilibrium processes in addition to the direct ejection of excited SO from the (stealth and other) volcanic vents.
![fluctus limbs fluctus limbs](https://vignette.wikia.nocookie.net/warframe/images/3/37/FactionSigilAssassinsLevel8.png)
We suggest that the emissions are caused by a large number of stealth plumes, produced through the interaction of silicate melts with superheated SO₂ vapor at depth. In some cases the SO emissions either in the core or the wings of the emission band can be identified with volcanoes, but the largest areas of SO emissions usually do not coincide with known volcanoes. Both the spatial distribution and the spectral shape of the SO emission band vary considerably across Io and over time. We show its spatial distribution at a resolution of ~0.”12 and a spectral resolution of R ~ 2500, as well as disk-integrated spectra at a high spectral resolution (R ~ 15,000).
![fluctus limbs fluctus limbs](https://i.redd.it/tth4e6bmccb41.jpg)
We present observations obtained with the 10 m Keck telescopes of the forbidden SO a¹Δ → X³Σ⁻ rovibronic transition at 1.707 μm on Io while in eclipse.