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Abstract We present first results derived from the largest collection of contemporaneously recorded Jovian sodium nebula and Io plasma torus in [S II] 6731 Å images assembled to date. The data were recorded by the Planetary Science Institute's Io Input/Output observatory and provide important context to Io geologic and atmospheric studies as well as theJunomission and supporting observations. Enhancements in the observed emission are common, typically lasting 1–3 months, such that the average flux of material from Io is determined by the enhancements, not any quiescent state. The enhancements are not seen at periodicities associated with modulation in solar insolation of Io's surface, thus physical process(es) other than insolation‐driven sublimation must ultimately drive the bulk of Io's atmospheric escape. We suggest that geologic activity, likely involving volcanic plumes, drives escape. 

Abstract Ultrahot Jupiters (UHJs) are likely doomed by tidal forces to undergo orbital decay and eventual disruption by their stars, but the timescale over which this process unfolds is unknown. We present results from a long-term project to monitor UHJ transits. We recovered WASP-12 b’s orbital decay rate of $\dot{P}=-29.8\pm 1.6$ms yr⁻¹, in agreement with prior work. Five other systems initially had promising nonlinear transit ephemerides. However, a closer examination of two—WASP-19 b and CoRoT-2 b, both with prior tentative detections—revealed several independent errors with the literature timing data; after correction, neither planet shows signs of orbital decay. Meanwhile, a potential decreasing period for TrES-1 b, $\dot{P}=-16\pm 5$ms yr⁻¹, corresponds to a tidal quality factor $Q_{\star }^{\prime }=160$and likely does not result from orbital decay if driven by dissipation within the host star. Nominal period increases in two systems, WASP-121 b and WASP-46 b, rest on a small handful of points. Only 1/43 planets (WASP-12 b) in our sample is experiencing detectable orbital decay. For nearly half (20/42), we can rule out $\dot{P}$as high as observed for WASP-12 b. Thus, while many UHJs could still be experiencing rapid decay that we cannot yet detect, a sizable subpopulation of UHJs are decaying at least an order of magnitude more slowly than WASP-12 b. Our reanalysis of Kepler-1658 b with no new data finds that it remains a promising orbital decay candidate. Finally, we recommend that the scientific community take steps to avoid spurious detections through better management of the multi-decade-spanning data sets needed to search for and study planetary orbital decay.