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Ganymede is the only known moon with an active dynamo. No mission has discovered intrinsic magnetism at the other Galilean satellites: Io, Europa, and Callisto. A dynamo requires a large magnetic Reynolds number, which in turn demands, for these moons, a large metallic core that is cooling fast enough for convection. Here we quantify these requirements to construct a regime diagram for the Galilean satellites. We compute the internal heat fluxes that would sustain a dynamo over the wide ranges of plausible radii for their metallic cores. Below a critical radius, no plausible heat flux will sustain a dynamo. Europa likely sits on the opposite side of this limit than Ganymede and Io. We predict that future missions may confirm a small (or absent) core, meaning that Europa could not sustain a dynamo even if its interior were cooling as quickly as Ganymede's core. Plain Language Summary: In the late 1990s, the NASA Galileo spacecraft visited the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto. Many studies interpret the Galileo gravity and magnetic field data to mean that: (a) Ganymede's intrinsic magnetic field arises from convection in a liquid metal core (i.e., a "dynamo" that converts mechanical energy into electromagnetic energy), (b) Europa has a metal core that is somehow incapable of generating a detectable magnetic field, and (c) Callisto may not have a metal core at all. Indeed, Ganymede is the only moon in our solar system known to sustain an active dynamo. Confirming the presence (or absence) of core convection provides us with valuable insight into the moons' structural and thermal history. In this study, we show that Europa's and Callisto's metal core (if they exist) may be too small to produce a dynamo, even if they convect. Crucially, no celestial body is known to have a convecting metal core without sustaining a dynamo too, but Europa might be an exception. Recently launched missions such as NASA's Europa Clipper and ESA's JUICE may test whether a small core size can explain the absence of dynamos at Europa and Callisto. Key Points: Dynamos in the Galilean moons would require both a dynamo‐producing region thicker than ∼250 km and core heat fluxes above ∼3 mW m−2Ganymede and Io probably have larger metallic cores than Europa and Callisto, but all satellites likely have similar core compositionsA small core could explain the absence of a strong dynamo at Europa even if Europa and Ganymede have similar core heat fluxes [ABSTRACT FROM AUTHOR]

We investigate the variability of the power emission of Io's hotspots by using recent Juno/JIRAM infrared observations. The Jovian Infrared Auroral Mapper (JIRAM) is an imaging spectrometer which began observing Jupiter in August 2016. Although observing Jupiter's moons is not its primary objective, JIRAM can use the frequent opportunities to observe Io (up to once per orbit) to gather infrared images and spectra of its surface. The present study uses the data acquired by JIRAM during the last 2 years, including the location and morphology of Io's hotspots, and the temporal variability of the total output. A new photometric model for the hotspots and the dayside surface has been developed, which permits us to disentangle the temporal variability from the changes in the observation geometry. While the latitudinal dependence of the power output is not well constrained, low-latitude hotspots show a significantly more intense temporal variability and greater temperature. [ABSTRACT FROM AUTHOR]

Abstract Juno performed close flybys of the innermost Galilean moon, Io, in December 2023 (I57) and February 2024 (I58). During these flybys, the radio link connecting the Juno spacecraft to Earth observing stations of NASA's Deep Space Network (DSN) propagated through the Alfvén wing, a magnetospheric feature in which plasma is produced between Io and Jupiter. The radio link is sensitive to the elevated electron densities in the Alfvén wing. A direct measurement of the total electron content was made by a linear combination of Juno's X‐band and Ka‐band downlink frequencies. Two different approaches were used in inverting the measurements into electron densities which assume different electron density distributions within the Alfvén wing. The maximum electron densities estimated in the Alfvén wing were 20,500–27,000 cm−3 on I57, in the northern Alfvén wing, and 15,300–31,000 cm−3 on I58, in the southern Alfvén wing.

Abstract We report on 0.032–32 keV electron observations during two Juno flybys of Io on 30 December 2023 and 3 February 2024. The first explored Io's northern Alfvén wing, the second covering its downstream region, south of the plasma wake. Both had closest approach altitudes of ∼1,500 km. Lower fluxes of >32 eV electrons in the Io torus transitioned to higher fluxes of energized, field‐aligned electrons within these regions. The electron fluxes were spatially variable within the Alfvén wing, highest at the boundaries, the distributions evolving from bi‐directional to mono‐directional as Juno traversed this region. Electron fluxes in the downstream region were also field‐aligned, energized, and comparable to those during the northern flyby, supporting the interpretation of a glancing encounter with the southern Alfvén wing. The electron energy flux in these regions ranged from 1–15 and 2–22 mW m−2, respectively, which are enhanced compared to estimates from Galileo.

Abstract The distribution of volcanic thermal emission on Io might reflect the location and magnitude of tidal heating, so it is important to accurately identify Io’s volcanoes to enable robust interior modeling. Zambon et al. (2023, https://doi.org/10.1029/2022gl100597) “Io Hot Spot Distribution Detected by Juno/JIRAM,” Geophysical Research Letters, 50, e2022GL100597 (2023) report the positions of hot spots on Io at high latitudes that are apparently spurious. This appears to be due to mis‐registration of JIRAM images to a frame of reference, leading to the same hot spot being located in different positions on Io’s surface. Other hot spots are not identified. The outcome of these additional and missing detections is a skewing of volcanic activity toward high latitudes, suggesting more polar activity than that seen at lower latitudes. This distribution of thermal sources would support a preponderance of deep mantle tidal heating, a conclusion not supported by other analyses of the same data.

Juno has allowed clear, high‐resolution imaging of Io's polar volcanoes using the Jovian Infrared Auroral Mapper (JIRAM) instrument. We have used data from JIRAM's M‐band (4.78 μm) imager from 11 Juno orbits to construct a global map of volcanic flux. This map provides short‐term insight into the spatial distribution of volcanoes and the ways in which high‐ and low‐latitude volcanoes differ. Using spherical harmonic analysis, we quantitatively compare our volcanic flux map to the surface heat flow distribution expected from models of Io's tidal heat deposition (summarized in de Kleer, Park, et al. (2019, https://doi.org/10.26206/d4wc‐6v82). Our observations confirm previously detected systems of bright volcanoes at high latitudes. Our study finds that both poles are comparably active and that the observed flux distribution is inconsistent with an asthenospheric heating model, although the south pole is viewed too infrequently to establish reliable trends. Plain Language Summary: Our study uses data from an infrared camera on Juno called the Jovian Infrared Auroral Mapper (JIRAM) to image Io, the innermost Galilean moon of Jupiter. Io is the most volcanically active body in the Solar System. Io's volcanoes are powered by both the extreme tides from Jupiter and the gravitational interactions between it and Jupiter's other moons. These tides generate friction inside Io. Simulations of Io's interior suggest that, depending on how deep that friction is being generated, the surface heat flow will be higher in certain areas (de Kleer, Park, et al., 2019, https://doi.org/10.26206/d4wc‐6v82). Using JIRAM, we have mapped where volcanoes are producing the most power and compared that to where we expect higher heat flow from the interior models. Our map doesn't agree with any of these models very well. JIRAM observed more volcanic activity at the poles than we expected to see based on previous observations. However, since the south pole was only observed twice, it's possible that these observations don't represent the average volcanic activity of the south pole. Very bright volcanoes that may have been continuously active for decades were also imaged during these Juno fly‐bys, some of which are nearer the poles than the equator. Key Points: We have produced a global volcanic flux map of Io using data from 11 Juno fly‐bysOur flux map doesn't agree well with tidal heat flow models reported in de Kleer, Park, et al. (2019, https://doi.org/10.26206/d4wc‐6v82)The M‐band flux is anti‐correlated with the asthenospheric heating model and has only very weak agreement with the global magma ocean model [ABSTRACT FROM AUTHOR]

Ovid's depiction of rape in the Metamorphoses has been interpreted as empathetic and proto-feminist at one extreme and pornographic at the other. In assessing this question, the current paper turns to trauma theory, a psychoanalytic methodology of growing popularity in the field of Classics, to demonstrate how Ovid depicts sexual violence and its aftermath with psychological acuity by emphasizing the mental, emotional, and physical experiences of rape survivors. I focus on the myth of Io, with parallels drawn to Daphne, Syrinx, Callisto, Proserpina, and Philomela. While cautiously supporting "optimistic" interpretations of the poem, this reading proves useful, regardless of authorial intent, in developing empathy-driven research and instruction in Classics courses and beyond. [ABSTRACT FROM AUTHOR]

On days 2023‐364 and 2024‐034, the Juno spacecraft made close passages of Jupiter's moon Io, at altitudes of about 1,500 km. Data obtained from the first flyby, when the spacecraft was on magnetic field lines connected to both Jupiter and Io, revealed deep flux decreases. In addition, Juno's energetic particle detectors observed tens to hundreds of keV electron and proton beams. Such beams could be generated near Jupiter on field lines associated with Io. The second encounter occurred in the plasma wake and a more modest flux decrease was observed. Furthermore, data from both encounters suggest a spatially extensive decrease in >1 MeV electrons that includes regions inward of Io's orbit. In the immediate vicinity of Io, signatures of absorption likely dominate the data whereas diffusion and wave‐particle interactions are expected to be needed to understand MeV electron data in the wider spatial region around Io. Plain Language Summary: Jupiter's magnetospheric plasma overtakes Io in its orbit. This causes a cavity to be formed over the hemisphere of Io that leads its orbital motion. Within this cavity subtle details of the plasma and energetic charged particle environment can be extracted from the signal, usually dominated by radiation at these distances. Examples include beams traveling in the direction from Jupiter to the moon, with little evidence of reflection at Io. Another major finding of this work is that there is a large region both along Io's orbit and even radially inward of it with a lower level of MeV electron flux. Guided by previous modeling, the most likely candidates for shaping the data are absorption by the moon, wave‐particle interactions that can scatter particles into Jupiter's atmosphere, and diffusion. Key Points: Deep flux decreases over Io and in its immediate wake caused by losses to the moon's surface were observed in Juno JEDI dataJuno JEDI detected narrow field‐aligned beams of electrons and protons directed toward Io's north poleMoon absorption and wave‐particle interactions may explain the loss of >1 MeV electrons that extend both inward and outward of Io's orbit [ABSTRACT FROM AUTHOR]

Along the I24, I27, and I31 flybys of Io (1999–2001), the Energetic Particle Detector (EPD) onboard the Galileo spacecraft observed localized regions of energetic protons losses (155–1,250 keV). Using back‐tracking particle simulations combined with a prescribed atmospheric distribution and a magnetohydrodynamics (MHD) model of the plasma/atmosphere interaction, we investigate the possible causes of these depletions. We focus on a limited region within two Io radii, which is dominated by Io's SO2 atmosphere. Our results show that charge exchange of protons with the SO2 atmosphere, absorption by the surface and the configuration of the electromagnetic field contribute to the observed proton depletion along the Galileo flybys. In the 155–240 keV energy range, charge exchange is either a major or the dominant loss process, depending on the flyby altitude. In the 540–1,250 keV range, as the charge exchange cross sections are small, the observed decrease of the proton flux is attributed to absorption by the surface and the perturbed electromagnetic fields, which divert the protons away from the detector. From a comparison between the modeled losses and the data we find indications of an extended atmosphere on the day/downstream side of Io, a lack of atmospheric collapse on the night/upstream side as well as a more global extended atmospheric component (>1 Io radius). Our results demonstrate that observations and modeling of proton depletion around the moon constitute an important tool to constrain the electromagnetic field configuration around Io and the radial and longitudinal atmospheric distribution, which is still poorly understood. Plain Language Summary: Io is a moon of Jupiter with active volcanoes and an atmosphere of which the structure and variability is poorly understood. A fascinating object on its own, neutral gas from Io also serves as the main source of plasma in Jupiter's magnetosphere. Improving our understanding of Io's atmosphere will allow us to better understand the precise link between Io's neutral environment and the plasma torus surrounding Jupiter. In this work we analyze data from the historic Galileo spacecraft that encountered Io. Specifically, we analyze regions close to Io where (normally abundant) energetic protons are disappearing. We find that charge exchange between these particles and Io's atmosphere along with the effect of the electric and magnetic fields on the paths of these particles can cause such decreases. Charge exchange with the atmosphere is either a major or the dominant source of losses, depending on the flyby altitude. The losses of the protons are related to Io's atmosphere and hint at an atmosphere that is more extended on Io's day side (also the downstream side from the plasma flow's point of view), doesn't collapse fully on the night (upstream) side, and appears to be more extended than we assumed. Key Points: Atmospheric charge exchange is a major or dominant loss process of energetic protons (155–224 keV) during three close Galileo flybys of IoProton losses suggest an expanded atmosphere on the day/downstream side and a lack of atmospheric collapse on the night/upstream sideDiscrepancies between the data and model hint at a global large scale height atmosphere [ABSTRACT FROM AUTHOR]

We used data from the Juno spacecraft to investigate both the spatial and temporal properties of Loki Patera on Io, acquired in two infrared bands between 2022 December and 2024 April, at pixel sizes ranging from 400 m to 15 km. Loki shows a thermal structure unlike other active lava lakes previously reported, with some brightening near the lake’s perimeter but lacking the continuous “hot ring” seen at other paterae. Modeling the slow rate of cooling suggests there is a significant volume of magma beneath the crust to provide the latent heat necessary to decelerate the cooling. A thermal propagation that may represent the signature of a resurfacing wave, going from the southwest of the lake to the north, was observed with a velocity of ∼2–3 km day ^−1 . Data collected in 2024 may indicate the onset of a new resurfacing wave originating from a point source, rather than the foundering of a linear section of the crust. We also observed many small (∼3 km wide), closely spaced (∼10 km apart) islands that have persisted in the same locations for at least 45 years, since first being imaged by Voyager 1. The persistence of these islands challenges resurfacing models of Loki, as they have remained fixed—likely anchored to the lava lake floor—and have not noticeably changed in size, arguing against large-scale thermal erosion. The central island of Loki shows a few thermal structures associated with the fractures that cross the island, indicating that the fractures most likely contain molten lava.

Since volcanic activity was first discovered on Io from Voyager images in 1979, changes on Io's surface have been monitored from both spacecraft and ground‐based telescopes. Here, we present the highest spatial resolution images of Io ever obtained from a ground‐based telescope. These images, acquired by the SHARK‐VIS instrument on the Large Binocular Telescope, show evidence of a major resurfacing event on Io's trailing hemisphere. When compared to the most recent spacecraft images, the SHARK‐VIS images show that a plume deposit from a powerful eruption at Pillan Patera has covered part of the long‐lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth‐based telescopes. The SHARK‐VIS instrument ushers in a new era of high resolution imaging of Io's surface using adaptive optics at visible wavelengths. Plain Language Summary: A new instrument, called SHARK‐VIS, on the Large Binocular Telescope in Arizona, has obtained high spatial resolution, visible wavelength images of Io, the highly volcanic moon of Jupiter. Large multicolored plume deposits were imaged, revealing where the red deposit from a volcano named Pele was covered by another plume deposit from another volcano, named Pillan Patera, the site of a powerful eruption in 2021. SHARK‐VIS ushers in a new age in planetary imaging. Key Points: High resolution images taken with SHARK‐VIS at LBT reveal low and high albedo features obscuring a portion of Pele's red ring on IoThis new eruption deposit likely originated from a powerful eruption in August 2021 located at Pillan PateraSuch images provide a new imaging capability that yields vital context to other observations of planetary surfaces [ABSTRACT FROM AUTHOR]

We investigate the tidal dissipation in Io's hypothetical fluid magma ocean using a new approach based on the solution of the 3D Navier‐Stokes equations. Our results indicate that the presence of a shallow magma ocean on top of a solid, partially molten layer leads to an order of magnitude increase in dissipation at low latitudes. Tidal heating in Io's magma ocean does not correlate with the distribution of hot spots, and is maximum for an ocean thickness of about 1 km and a viscosity of less than 104 Pa s. Due to the Coriolis effect, the k2 Love number can depend on the harmonic order. We show that the analysis of k2 may not reveal the presence of a fluid magma ocean if the ocean thickness is less than 2 km. If the fluid layer is thicker than 2 km, k20 ≈ k22/2 ≈ 0.7. Plain Language Summary: Jupiter's moon Io is the most active volcanic body in the Solar System. Although it is generally accepted that Io's volcanic activity is driven by the heat generated by tidal friction, the origin and the distribution of tidal heating within Io's interior remain a subject of debate. Here we investigate the tidal dissipation in Io's hypothetical fluid magma ocean using a new approach based on the solution of general equations describing the motion of viscous fluid. Our results indicate that the presence of a shallow magma ocean on top of a solid, partially molten layer leads to an order of magnitude increase in dissipation at low latitudes. Tidal heating in Io's magma ocean does not correlate with the distribution of hot spots, and is maximum for an ocean thickness of about 1 km and a viscosity of less than 104 Pa s. We also discuss the sensitivity of Io's gravity signature to the presence of a magma ocean and provide estimates of gravitational perturbations induced by tidal deformation. Key Points: The presence of a shallow magma ocean on top of a partially molten layer leads to a strong increase in tidal dissipation at low latitudesDue to the Coriolis effect, the degree‐2 Love numbers for models with a magma ocean can depend on the harmonic orderThe tidal Love numbers are not sensitive to the presence of a fluid magma ocean if the thickness of the fluid layer is less than 2 km [ABSTRACT FROM AUTHOR]

We investigated how spatial variations in tidal heating affect Io's isostatic topography at long wavelengths. The long‐wavelength relief is less than the 0.3 km uncertainty in Io's global shape. Assuming Airy isostasy, degree‐2 topography <0.3 km amplitude is only possible if surface heat flux varies spatially by <19% of the mean value. This is consistent with Io's volcano distribution and is possible if tidal heat is generated within and redistributed by a convecting layer underneath the lithosphere. However, that layer would require a viscosity <1010 Pa s. A magma ocean would have low enough viscosity but would not generate enough tidal heat internally. Conversely, assuming Pratt isostasy, we found ∼0.15 km degree‐2 topography is easily achievable. If a magma ocean was present, Airy isostasy would dominate; we therefore conclude that Io is unlikely to possess a magma ocean. Plain Language Summary: As it orbits Jupiter elliptically, the difference in gravitational pull experienced by the moon Io results in tidal heating due to internal friction. Some evidence suggests this heat forms a magma ocean beneath Io's crust. If so, there would be a difference in the amount of heat generated at Io's equator versus its poles and would alter the thickness of Io's crust between the two locales. Assuming the crust has a uniform density, its thickness would be inversely proportional to the tidal heat beneath the crust, which in turn affects the difference in Io's radius at the equator versus at its poles. However, reasonable variation in tidal heating across Io would result in a greater difference in radius than is observed. The difference in observed radius is more likely if variation in tidal heat across Io affects crustal density rather than crustal thickness. Then, it is more likely that Io does not have a magma ocean. Key Points: Long‐wavelength relief implies low spatial variation in Io's tidal heating when assuming Airy isostasyTidal heat produced in a convecting aesthenosphere can reduce spatial variation in tidal heating, but requires prohibitively low viscosityIo's topography is consistent with expected tidal heating spatial variations if thermal expansion drives crustal density variations [ABSTRACT FROM AUTHOR]

Io, the closest of Jupiter's four Galilean moons, suffers from intense ion bombardment from Jupiter's magnetosphere. The constant atmospheric erosion by energetic ion precipitation, referred to atmospheric sputtering, serves as an important mechanism of Io's atmospheric escape. This study is devoted to a state‐of‐the‐art study of atmospheric sputtering at Io, with the aid of constantly accumulated understandings of Io's space environment and atmospheric photochemistry, as well as the updated laboratory measurements. A Monte Carlo model is constructed to track the energy degradation of incident S++ and O+ and atmospheric recoils from which the sputtering yields of different atmospheric species are determined. Our calculations suggest a total escape rate of 3 × 1029 atom s−1 on Io, and SO2 is the dominant sputtered species. Further investigations reveal that S++ is the most efficient species for atmospheric sputtering on Io, and sputtering yields increase substantially with increasing incident ion mass, energy, and incidence angle. The model sensitivity to different influence factors is also discussed, including scattering angle distribution, atmospheric column density, proton precipitation, inelastic process, and surface sputtering, of which the former two dominate. Plain Language Summary: As the closest Galilean moon of Jupiter, Io is strongly influenced by high energy ions from Jupiter's magnetosphere. The collisions between these high energy ions and background atmospheric particles can produce considerable high energy atmospheric recoils. A large portion of these particles are able to escape to space when their kinetic energies exceed local escape energy. Such a phenomenon is named atmospheric sputtering. In this study, we simulate this process on Io with the aid of parameters from laboratory measurements and a Monte Carlo model. Our calculations show that sputtering is the most important process driving atmospheric loss at Io. We also analyze the effects of various incident plasma populations and model setups on the atmospheric sputtering at Io. Key Points: Atmospheric sputtering is the most important mechanism driving atmosphere escape at IoOur calculations suggest a total escape rate of 3 × 1029 atom s−1 on IoSputtering yields vary substantially with incident plasma and atmospheric conditions, yet are insensitive to proton precipitation and inelastic process [ABSTRACT FROM AUTHOR]

Background: Understanding how to modulate the microenvironment of tumors that are resistant to immune checkpoint inhibitors represents a major challenge in oncology.Here we investigate the ability of USP7 inhibitors to reprogram the tumor microenvironment (TME) by inhibiting secretion of vascular endothelial growth factor (VEGF) from fibroblasts. Methods: To understand the role played by USP7 in the TME, we systematically evaluated the effects of potent, selective USP7 inhibitors on co‐cultures comprising components of the TME, using human primary cells. We also evaluated the effects of USP7 inhibition on tumor growth inhibition in syngeneic models when dosed in combination with immune checkpoint inhibitors (ICIs). Results: Abrogation of VEGF secretion from fibroblasts in response to USP7 inhibition resulted in inhibition of tumor neoangiogenesis and increased tumor recruitment of CD8‐positive T‐lymphocytes, leading to significantly improved sensitivity to immune checkpoint inhibitors. In syngeneic models, treatment with USP7 inhibitors led to striking tumor responses resulting in significantly improved survival. Conclusions: USP7‐mediated reprograming of the TME is not linked to its previously characterized role in modulating MDM2 but does require p53 and UHRF1 in addition to the well‐characterized VEGF transcription factor, HIF‐1α. This represents a function of USP7 that is unique to fibroblasts, and which is not observed in cancer cells or other components of the TME. Given the potential for USP7 inhibitors to transform "immune desert" tumors into "immune responsive" tumors, this paves the way for a novel therapeutic strategy combining USP7 inhibitors with immune checkpoint inhibitors (ICIs). [ABSTRACT FROM AUTHOR]

Stable isotope fractionation of sulfur offers a window into Io's tidal heating history, which is difficult to constrain because Io's dynamic atmosphere and high resurfacing rates leave it with a young surface. We constructed a numerical model to describe the fluxes in Io's sulfur cycle using literature constraints on rates and isotopic fractionations of relevant processes. Combining our numerical model with measurements of the 34S/32S ratio in Io's atmosphere, we constrain the rates for the processes that move sulfur between reservoirs and model the evolution of sulfur isotopes over time. Gravitational stratification of SO2 in the upper atmosphere, leading to a decrease in 34S/32S with increasing altitude, is the main cause of sulfur isotopic fractionation associated with loss to space. Efficient recycling of the atmospheric escape residue into the interior is required to explain the 34S/32S enrichment magnitude measured in the modern atmosphere. We hypothesize this recycling occurs by SO2 surface frost burial and SO2 reaction with crustal rocks, which founder into the mantle and/or mix with mantle‐derived magmas as they ascend. Therefore, we predict that magmatic SO2 plumes vented from the mantle to the atmosphere will have lower 34S/32S than the ambient atmosphere, yet are still significantly enriched compared to solar‐system average sulfur. Observations of atmospheric variations in 34S/32S with time and/or location could reveal the average mantle melting rate and hence whether the current tidal heating rate is anomalous compared to Io's long‐term average. Our modeling suggests that tides have heated Io for >1.6 Gyr if Io today is representative of past Io. Plain Language Summary: Io is a moon of Jupiter and is the most volcanically active body in our solar system. Io is in an orbital resonance with two other large moons of Jupiter; Europa and Ganymede: every time Ganymede orbits Jupiter once, Europa orbits twice, and Io orbits four times. This situation causes tidal heating in Io (like how the Moon causes ocean tides on Earth), which causes the volcanism. We do not know how long this resonance has been occurring and whether what we observe today is "normal." This is because the volcanism renews Io's surface all the time, leaving little trace of the past. We use the isotopes of sulfur as a tracer of tidal heating on Io because sulfur is released through volcanism, processed in the atmosphere, and recycled into the mantle. We build a numerical model to simulate the sulfur isotope cycle on Io. Recent measurements of the sulfur isotopic composition of Io's atmosphere allow us to constrain a likely evolution for Io over time. We find that tidal heating on Io has occurred for billions of years and that the variability of the sulfur isotopic composition of the atmosphere may indicate the average tidal heating rate on Io. Key Points: Rayleigh distillation, where gravitational stratification drives isotopic fractionation, is a good approximation for Io's sulfur isotope cycleEfficient mixing and recycling between Io's interior and atmosphere occurs by crustal sequestration, volcanic frost remobilization, and burial into the mantleThe difference between mantle and crustal frost 34S/32S decreases as mantle melting rate increases; atmospheric variability could measure this [ABSTRACT FROM AUTHOR]

Printed Circuit Board (PCB) defect detection is crucial for ensuring the quality and reliability of electronic devices. The study proposes an enhanced YOLOv5s model for PCB defect detection, which combines Coordinate Attention (CA), Convolutional Block Attention Module (CBAM), and Inception-style convolutions (IO). This model aims to improve the detection accuracy of small defects while reducing computational complexity. Experiments on the PCB defect dataset demonstrate that the proposed CA-CBAM-IOYOLOv5s model achieves higher accuracy (97.8%), recall (98.6%), and F1 score (98.3%) compared to the basic YOLOv5s and other state-of-the-art models. The model also shows excellent performance in detecting various types of PCB defects, with an average detection accuracy of 98.45% and an average detection time of 0.114 seconds. These results indicate that the proposed model provides a promising solution for efficient and accurate PCB defect detection in industrial applications.

The Juno spacecraft had previously observed intense high frequency wave emission, broadband electron and energetic proton energy distributions within magnetic flux tubes connected to Io, Europa, Ganymede, and their wakes. In this work, we report consistent enhancements in <46 keV energy proton fluxes during these satellite flux tube transit intervals. We find enhanced fluxes at discrete energies linearly separated in velocity for proton distributions within Io wake flux tubes, and both proton and electron distributions within Europa and Ganymede wake flux tubes. We propose these discrete enhancements to be a result of resonances between particles' bounce motion with standing Alfvén waves generated by the satellite‐magnetosphere interaction. We corroborate this hypothesis by comparing the bounce and field‐line resonance periods expected at the satellites' orbits. Hence, we find bounce‐resonant acceleration is a fundamental process that can accelerate particles in Jupiter's inner magnetosphere and other astrophysical plasmas. Plain Language Summary: The passage of the Galilean moons‐ Io, Europa, Ganymede, and Callisto, perturbs the plasma flow in Jupiter's magnetosphere, creating waves that travel from the moon and reflect off Jupiter's ionosphere. These waves have been proposed to accelerate charged particles, and such accelerated particles had been observed by the Juno spacecraft during its passage through magnetic field lines connected to the satellite wakes. In this work, we find instances when this acceleration occurs selectively at specific energies that have constant separation in speed. We propose that this selective acceleration is due to resonance between particle bounce motion and the waves arising from the satellite wake perturbation. Bounce‐resonant acceleration is a promising fundamental process which can accelerate particles in Jupiter's inner magnetosphere and other plasma systems with similar geometries. Key Points: Proton and electron flux enhancements in satellite and wake flux tubes often occur at discrete energies linearly separated in speedBroadband proton flux enhancements at <46 keV energies were also observed within satellite flux tube crossingsParticles can be accelerated via resonance between bounce motion and standing Alfvén waves generated by moon‐magnetosphere interactions [ABSTRACT FROM AUTHOR]

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 the Juno mission 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. Plain Language Summary: The Planetary Science Institute's Io Input/Output observatory (IoIO) is composed almost entirely of off‐the‐shelf parts popular with amateur astronomers. IoIO uses special filters to isolate emission from two gasses found around Jupiter: neutral sodium and ionized sulfur. The sodium is thrown out from Io in a vast cloud called the Jovian sodium nebula. The ionized sulfur collects into the Io plasma torus (IPT), a ring‐shaped structure centered around Jupiter that wobbles around Io's orbital path. These gasses ultimately come from Jupiter's highly volcanic moon, Io. We see the Na nebula and IPT brighten frequently. This demonstrates that the majority of the material leaving Io comes from whatever drives the frequent brightening events, with volcanic plumes likely playing a key role. Our results challenge a widely held belief in the scientific community, that the majority of the material in the Na nebula and IPT comes from Io's tenuous global atmosphere, which is fed by the sublimation of surface frosts and is relatively stable in time. Our data set also provides important context for NASA's Juno mission and supporting observations that focus on Io volcanism, the material's likely source, and Io's magnetosphere, the material's ultimate destination. Key Points: A large set of Jovian sodium nebula and Io plasma torus S+ images provides context for Io and Jovian magnetospheric studiesEnhancements in Na and S+ emission last 1–3 months, ruling out insolation‐driven sublimation as their driverVolcanic plumes likely play a key role in atmospheric escape [ABSTRACT FROM AUTHOR]

In 1995, the Galileo spacecraft traversed the wake of Io at ∼900 km altitude. The instruments onboard detected intense bi‐directional field‐aligned electron beams (∼140 eV–150 keV), embedded in a dense, cold and slow plasma wake (Nel ∼ 35,000 cm−3, Ti < 10 eV, V < 3 km/s). Similar electron beams were also detected along subsequent Galileo flybys. Using numerical simulations, we show that these electron beams are responsible for the formation of Io's dense plasma wake. We prescribe the composition of Io's atmosphere in S, O, SO and SO2, compute the atmospheric ionization by the beams with a parameterization adapted from study of auroral electrons at Earth, the plasma flow into Io's atmosphere with a Magneto‐Hydro‐Dynamic code, and the ion composition and temperature with a multi‐species physical chemistry code. Results reveal contrasting chemistries between the upstream and wake regions, leading to different ion compositions. The upstream chemistry is driven by the torus thermal electrons at 5 eV with SO2+ becoming the dominant ion because of electron‐impact ionization of the SO2 atmosphere. The wake chemistry is driven by the high‐energy electrons in the beams with S+ and SO+ becoming the dominant ions produced by dissociative‐ionization of SO2. We show that the wake ion composition is highly sensitive to the atmospheric composition. Juno, in its extended mission, will traverse Io's wake and determine its ion composition, which, compared with our numerical simulations will enable us to infer the detailed composition of the atmosphere. Plain Language Summary: Io, the inner‐most Galilean moon of Jupiter, is the most active volcanic body of the solar system. It has a tenuous atmosphere ultimately supplied by volcanic activity. The atmosphere is mainly composed of sulfur dioxide, oxygen, sulfur and sulfur monoxide, but its detailed composition, density and spatial distribution are still surprisingly poorly known. Between 1995 and 2001, the Galileo spacecraft made five close flybys of Io. The onboard instruments detected intense high‐energy electrons moving along Jupiter's magnetic field lines embedded in a remarkably dense ion wake (∼10 times denser than the surrounding plasma). Identifying the processes that generate this dense wake remains an outstanding issue. We utilize numerical simulations to demonstrate that the production of the dense ion wake is attributed to efficient ionization of Io's atmosphere by the electron beams. Our simulations reveal that the ion composition of the wake is highly sensitive to the atmospheric composition. The Juno spacecraft, currently in orbit around Jupiter, will conduct several flybys in Io's wake in 2023 and 2024 and determine its ion composition. Similar electron beams are likely present near other moons of Jupiter. Such beams have already been detected during a single flyby of Europa by the Juno probe. The Jupiter Icy Moon Explorer spacecraft is presently en route to Ganymede and Callisto, while the future Europa Clipper mission is scheduled to be launched to Europa in 2024. These missions will have the capacity to detect the presence of electron beams and plasma wakes similar to those observed at Io. Our numerical model serves as an effective tool for inferring the atmospheric composition and density of these moons as it predicts the ion composition and density of the wake based on the energy of the electron beams. Key Points: The Galileo spacecraft detected a dense and cold plasma wake downstream of Io and intense field‐aligned high‐energy electron beamsUsing numerical simulations, we show that this dense plasma wake is produced by the electron beams ionization of Io's atmosphereThe ion composition and density in the wake strongly depend on Io's atmospheric density and its neutral composition [ABSTRACT FROM AUTHOR]

This paper is devoted to some aspects of the study of relativistic effects (geodetic precession and geodetic nutation, which together constitute geodetic rotation) in the rotation of celestial bodies of the Solar System using the example of Jupiter and its Galilean satellites (Io, Europa, Ganymede, and Callisto). The difference in the angular velocity vectors of geodetic rotation is shown depending on the choice of reference frame. Thus, the absolute value of the angular velocity vector of the geodetic rotation of the satellite under study relative to the barycenter of the Solar System will not coincide with the absolute value of a similar vector of the satellite under study relative to the barycenter of the planet's satellite system. As a result, the most significant secular and periodic terms of geodetic rotation were determined for the first time: a) of Jupiter and its Galilean satellites in terms of the Euler angles, in the perturbing terms of physical libration and in the absolute value of the angular rotation vector of the geodetic rotation of the body under study relative to the barycenter of the Solar System and the plane of the mean orbit of Jupiter of the epoch J2000.0; b) of Galilean satellites of Jupiter in the perturbing terms of physical libration and the absolute value of the angular rotation vector of the geodetic rotation of the studied body relative to the barycenter of the Galilean satellite system of Jupiter and the mean orbit plane of the studied Galilean satellite of the epoch J2000.0. The obtained analytical values of the geodetic rotation of the studied objects can be used for a numerical study of their rotation in the relativistic approximation, and also used to evaluate the influence of relativistic effects on the orbital–rotational dynamics of bodies of exoplanetary systems. [ABSTRACT FROM AUTHOR]

Background: Cannabis (CAN) use has risen significantly over the last few decades. CAN has potent immunosuppressive properties, which could antagonize the effect of immunotherapy (IO). The impact of CAN use on clinical cancer outcomes remains unclear. Objectives: In this study, we evaluated the clinical effect of CAN use on clinical outcomes among patients with solid malignancies receiving IO. Design: This is a retrospective cohort study of all patients with solid malignancies receiving IO between August 2014 and August 2018. Methods: Patients were stratified based on CAN use to CAN users and CAN non-users. The primary outcome was overall survival (OS), and the secondary outcomes were progression-free survival (PFS) and disease control rate (DCR). Univariable and multivariable logistic and Cox regression analyses were performed to compare the outcomes between the two groups, adjusting for covariates. Results: The records of 106 patients were reviewed, 28 (26%) of whom were CAN users and 78 (74%) were CAN non-users. One patient was excluded. Most CAN users consumed dronabinol (82%). The median follow-up for OS and PFS was 29.2 months. Median OS in the CAN users was 6.7 months compared to 17.3 months in the CAN non-users (HR, 1.78; 95% CI, 1.06–2.97; p = 0.029). The median PFS was 4.8 months in the CAN users compared to 9.7 months in the CAN non-users (HR, 1.74; 95% CI, 1.09–2.79; p = 0.021). DCR was 11% among CAN users and 38% among CAN non-users (OR, 0.23; 95% CI; 0.06–0.68; p = 0.007). An exploratory racial disparity analysis showed that this negative impact of CAN was primarily seen in White patients. Conclusion: In this single institutional experience, CAN use was associated with worse OS, PFS, and DCR among cancer patients receiving IO. Prospective trials are needed to further study this potential antagonistic interaction between CAN and IO and explore the racial disparities related to CAN exposure. Plain language summary: Impact of cannabis use on clinical outcomes in patients with cancer receiving immunotherapy Cannabis (CAN) use has risen significantly over the last few decades. The clinical effect of CAN consumption on cancer patients receiving immunotherapy (IO) remains unknown. In this study, we identified 106 cancer patients receiving IO. Patients who did not consume CAN lived longer than those who consumed CAN. Additionally, patients who consumed CAN were more likely for their cancer to recur and had more rapid cancer recurrence than those who did not. This unfavorable effect of CAN is predominantly seen in white patients. [ABSTRACT FROM AUTHOR]

We present spatially resolved measurements of SO _2 and NaCl winds on Io at several unique points in its orbit: before and after eclipse and at maximum eastern and western elongation. The derived wind fields represent a unique case of meteorology in a rarified, volcanic atmosphere. Through the use of Doppler shift measurements in emission spectra obtained with the Atacama Large Millimeter/submillimeter Array between ~346 and 430 GHz (~0.70–0.87 mm), line-of-sight winds up to ~−100 m s ^−1 in the approaching direction and >250 m s ^−1 in the receding direction were derived for SO _2 at altitudes of ~10–50 km, while NaCl winds consistently reached ~∣150–200∣ m s ^−1 in localized regions up to ~30 km above the surface. The wind distributions measured at maximum east and west Jovian elongations and on the sub-Jovian hemisphere pre- and posteclipse were found to be significantly different and complex, corroborating the results of simulations that include surface temperature and frost distribution, volcanic activity, and interactions with the Jovian magnetosphere. Further, the wind speeds of SO _2 and NaCl are often inconsistent in direction and magnitude, indicating that the processes that drive the winds for the two molecular species are different and potentially uncoupled; while the SO _2 wind field can be explained through a combination of sublimation-driven winds, plasma torus interactions, and plume activity, the NaCl winds appear to be primarily driven by the plasma torus.

This paper, which serves as the introduction to the volume, suggests that stories of ancient Roman women shattering the curtain of silence that surrounds them can be repurposed to support contemporary women's struggle to make their voice heard. In particular, the tales of Io and Philomela in Ovid's Metamorphoses can be used to amplify the powerful message of the recently developed Me Too movement, as they show that women victim of sexual assault can reaffirm their identity and reclaim their role in the community by speaking up and denouncing the violence they have suffered. [ABSTRACT FROM AUTHOR]

We observed Io with the James Webb Space Telescope (JWST) while the satellite was in eclipse, and detected thermal emission from several volcanoes. The data were taken as part of our JWST‐ERS program #1373 on 15 November 2022. Kanehekili Fluctus was exceptionally bright, and Loki Patera had most likely entered a new brightening phase. Spectra were taken with NIRSpec/IFU at a resolving power R ≈ 2,700 between 1.65 and 5.3 µm. The spectra were matched by a combination of blackbody curves that showed that the highest temperature, ∼1,200 K, for Kanehekili Fluctus originated from an area ∼0.25 km2 in size, and for Loki Patera this high temperature was confined to an area of ∼0.06 km2. Lower temperatures, down to 300 K, cover areas of ∼2,000 km2 for Kanehekili Fluctus, and ∼5,000 km2 for Loki Patera. We further detected the a1Δ ⇒ X3Σ− 1.707 µm rovibronic forbidden SO emission band complex over the southern hemisphere, which peaked at the location of Kanehekili Fluctus. This is the first time this emission has been seen above an active volcano, and suggests that the origin of such emissions is ejection of SO molecules directly from the vent in an excited state, after having been equilibrated at temperatures of ∼1,500 K below the surface, as was previously hypothesized. Plain Language Summary: We observed Io with JWST in November 2022 while the satellite was in Jupiter's shadow, and glowing volcanoes show up without being (partially) obscured by reflected sunlight. We detected the volcanoes Loki Patera and Kanehekili Fluctus; the latter was exceptionally bright, and Loki Patera had likely entered a new brightening phase. Both volcanoes show erupting lavas at temperatures of at least 1,200 K, originating at a vent of ∼0.25 km2 in size for Kanehekili Fluctus and <0.1 km2 for Loki Patera. In addition to lava, Kanehekili Fluctus spews out gases, and we detected, for the first time, SO emission at 1.707 μm right over the volcano. This is the first time this emission has been seen above an active volcano, and suggests that such emissions are produced by SO molecules immediately upon leaving the vent. Key Points: James Webb Space Telescope observations detected an energetic eruption at Kanehekili Fluctus, and a new brightening event at Loki PateraThe erupting lavas have a temperature of at least 1,200 K over an area of ∼0.25 km2 or lessWe detected, for the first time, a clear association of the 1.707 micron forbidden SO emissions with an active volcano [ABSTRACT FROM AUTHOR]

We have calculated surface‐leaving spectral radiances for 285 detections of volcanic thermal emission from Io observations made by the Galileo Near Infrared Mapping Spectrometer (NIMS) in the 0.7‐ – 5.2‐μm wavelength range, the first such analysis of the entire low‐spatial‐resolution night‐time data set. Most of these detections are of 53 individual hot‐spots. We establish that 4.8‐μm spectral radiance is a good proxy for total thermal emission from a hot spot. Many detections reported here have not been previously modeled. This set of hot‐spot detections is derived from NIMS night‐time observations obtained between June 1996 (orbit G1) and October 2001 (Orbit I32), where the hot‐spot is sub‐pixel. Modeling of the spectra yields total thermal emission from each volcano in each observation, as well as the 2:5‐μm spectral radiance ratio and radiant flux density. Surface‐leaving spectral radiance is derived at 2.0, 3.5, 3.8, 4.8, and 5.0 μm allowing direct comparison with data obtained by other spacecraft and ground‐based telescope data. The most energetic volcanic eruptions are identified. We find an unusual number of sources in a C30 observation suggesting that a vigorous volcanic activity was taking place simultaneously in multiple locations, possibly tidally controlled. Plain Language Summary: Io, a moon of Jupiter, is intensely volcanic, its surface dotted with hundreds of erupting volcanoes resulting from tidal forces that heat Io's interior. The distribution and variability of radiated heat from each volcano reveal how lava is erupted (the eruption style) and, more importantly, how much energy is being transported by volcanic activity across Io. We have processed the full Galileo spectrometer low‐spatial‐resolution, night‐time data set to determine, from 285 detections of volcanic activity, precisely how much energy has been emitted at different wavelengths in the infrared, where hot lava releases most energy, as well as each hot spot's total thermal emission contribution to Io's heat flow budget. The energy released is calculated at different wavelengths to allow direct comparison with data collected by other spacecraft and ground‐based telescopes. Other thermal emission properties are calculated that reveal the various eruption styles, including lava lakes and lava fountains, and a cluster of particularly vigorous eruptions is identified. We extend previous analyses to provide a comprehensive look at Io's hot spot activity in the infrared from Galileo data obtained at night. The thermal emission spectrum for each hot‐spot in this data set will soon be available from NASA's Planetary Data System. Key Points: We have modeled thermal emission from all 285 Galileo NIMS night time spectra where hot spots are sub‐pixelWe calculate surface‐leaving spectral radiance at 2, 3.5, 3.8, 4.8, and 5 μm, 2:5‐μm spectral radiance ratio, and radiant flux densitiesWe find an unusual set of vigorous eruptions taking place during Galileo Orbit C30, suggesting a possible tidal control on activity [ABSTRACT FROM AUTHOR]

This article aims to examine one of the myths belonging to the first part of Nonnus’ Dionysiaca, i.e., that of Io. Starting from the philological analysis of the passages dealing with this myth and adopting an intertextual approach, I will argue that the Panopolitan assimilates Io to Isis following Lycophron, one of the authors employed as a model in his poem. Finally, I will also explain the meaning of this choice inside Nonnus’ work, taking into account its historical context. Nonnus wants to emphasize the role of Dionysus’ lineage in the civilization process, giving it an historical relevance. Therefore, the allusion to Lycophron assimilates Cadmus (Dionysus’ grandfather) to Alexander the Great, who is celebrated as a peacemaker in the Alexandra. Furthermore, Cadmus and his offspring can be connected to the Romans, who, at the time of Nonnus, played the same role in the rising Byzantine empire.

The document is a corrigendum for an article on Io's hotspots, correcting references to various studies and authors. The corrections ensure accurate citations and do not impact the scientific conclusions of the original article. The authors are from various institutions in Italy, the United States, and other countries, emphasizing international collaboration in space research. [Extracted from the article]

Juno's highly inclined orbits provide opportunities to sample high‐latitude magnetic field lines connected to the orbit of Io, among the other Galilean satellites. Its payload offers both remote‐sensing and in‐situ measurements of the Io‐Jupiter interaction. These are at discrete points along Io's footprint tail and at least one event (12th perijove) was confirmed to be on a flux tube Alfvénically connected to Io, allowing for an investigation of how the interaction evolves down‐tail. Here we present Alfvén Poynting fluxes and field‐aligned current densities along field lines connected to Io and its orbit. We explore their dependence as a function of down‐tail distance and show the expected decay as seen in UV brightness and electron energy fluxes. We show that the Alfvén Poynting and electron energy fluxes are highly correlated and related by an efficiency that is fully consistent with acceleration from Alfvén wave filamentation via a turbulent cascade process. Plain Language Summary: Io and Jupiter are electrodynamically coupled resulting in the Io footprint tail. This is one of the most persistent, stable, and recognizable features of Jupiter's aurora. The Juno spacecraft routinely samples magnetic field lines connected to Io's orbit, allowing for an investigation of this powerful coupling. We use data recorded by Juno to estimate a proxy for the strength of this interaction, that is, electromagnetic energy, and show its dependence downstream of Io and how the interaction decays. We further show that the available electromagnetic energy and electron energy are intimately linked, suggesting a transfer of energy between wave and particles. This is the basis upon which electrons end up precipitating into Jupiter's upper atmosphere and generate some of the brightest auroras. Key Points: Alfvénic Poynting fluxes and electron energy fluxes are highly correlated on magnetic field lines connected to Io's orbitThe efficiency in the Main Alfvén Wing is ∼10%, fully consistent with Alfvén wave filamentation via a turbulent cascade processField‐aligned current densities are quantified and exhibit a decay in magnitude down‐tail of Io [ABSTRACT FROM AUTHOR]

Depending on the IO approaches the configuration of HONO, two different H-extraction pathways (IO + cis-HONO and IO + trans-HONO) were located at the CCSD(T)//ωB97X-D level. With the introduction of single water molecule, nine pathways were investigated for the IO + HONO reaction. The computed results manifested that the barriers of Pathway W11, Pathway W12, Pathway W21A, Pathway W21B, Pathway W22B, and Pathway W23 are reduced by 0.39, 3.05, 8.14, 12.63, 13.13, and 10.02 kcal/mol, respectively. The rate coefficients of the reaction of IO + cis-HONO and IO + trans-HONO at 298.15 K in the existence of water are 5.98 × 10−13 and 4.93 × 10−11 cm−3 molecule−1 s−1, which are lower than the corresponding reactions in the absence of water (1.14 × 10−14 and 1.39 × 10−19 cm−3 molecule−1 s−1). To further comprehend the influence of H2O on the IO + HONO reaction, the effective rate coefficients were computed through taking account on the water concentration. The effective rate coefficients of the IO + trans-HONO reaction are much larger than the IO + trans-HONO reaction in the absence of water, 'as water molecule could cause the inhibition of the IO + cis-HONO reaction. In contrast to the IO + HONO reaction with water-free, the feasible reaction is the IO + trans-HONO instead of the IO + cis-HONO reaction. The current investigation proved that water possesses positive influence on the IO + trans-HONO reaction, which could devote to the degradation of HONO. [ABSTRACT FROM AUTHOR]

The New Astrometric Reduction of Old Observations (NAROO) program is dedicated to the measurement of astrophotographic plates and the analysis of old observations for scientific purposes. One of the main objectives of the NAROO program is to provide accurate positional measurements of planets and satellites to improve our knowledge of their orbits and dynamics, and to infer the accuracy of the planet and satellite ephemerides. We digitized 553 astronegatives of the Galilean satellites taken with the McCormick 26-inch refractor in 1967/68 and the U.S. Naval Observatory 26-inch refractor from 1973 to 1998, resulting in 2650 individual observations. We measured and reduced these observations through an optimal process that includes image, instrumental, and spherical corrections using Gaia-DR3 catalog to provide the most accurate equatorial (RA, Dec) ICRS (Gaia-CRF3) positions. 4819 positions of the Galilean satellites have been determined with an accuracy of 55 mas (160 km at Jupiter), near the limit of the photographic technique for such work. These data can help to improve the equatorial positions of Jupiter. They also can be used in the context of quantifying tidal effects and will still be useful when Europa Clipper and Juice data will become available. • Analysis of USNO Galilean astro-photographic plates 1967–1998. • Photographic plate digitization at the NAROO center. • Limit of the astro-photographic technique. • Equatorial ICRS (Gaia-CRF3) positions of Jupiter, Io, Europa, Ganymede, Callisto. [ABSTRACT FROM AUTHOR]

Successive observations of Jupiter's sodium nebula have identified several brightening events, presumably due to variability in Io's volcanic plumes. An event that began in the beginning of March 2018 has been already reported by Morgenthaler et al. (2019,2024a,2024b). In this work, we found that this event was followed by another one. By adding these observations, details of these events including one observed by Morgenthaler et al. (2019,2024a,2024b) are described herein. Especially, the event in 2018 seems to have been the strongest enhancement during Juno spacecraft's orbital mission, at least before 2020. Also, our observations show that the D-line brightness of the sodium nebula was decreasing in early September, 2019. This tendency is consistent with Io's volcanic plume activity observed by Atacama Large (sub)Millimeter Array (ALMA). The KCl gas observed in this plume with ALMA is a chemical analog of NaCl, which is believed to be the parent molecule that dissociates to form the sodium nebula. While these observations are not the direct evidence of plume supply to sodium nebula, they are suggestive of control of Io's volcanic plumes on the brightness of Jupiter's sodium nebula. [ABSTRACT FROM AUTHOR]

Recent ground-based Infrared Telescope Facility observations showed that a hot spot observed at the location of the surface feature Acala Fluctus was volcanically active for ∼18 months in 2019–2020 and exhibited two outbursts with a temperature of ∼1200 K. A high-temperature hot spot at Acala was also observed by Galileo SSI in the late 1990s over multiple flybys. Low-temperature hot spots in this area were detected in 2000 by the Galileo Photopolarimeter Radiometer and in 1979 by Voyager IRIS. However, neither the Galileo NIMS instrument nor any instrument on the New Horizons spacecraft, which flew by Io in 2007, saw any evidence of an Acala hot spot. It is also possible that earlier ground-based disk-integrated observations of hot spots are due to Acala, even though they were originally attributed to other volcanoes, such as Loki. These include outbursts in 1978 and 1990 and a persistent low-temperature source in the 1980 and 1990s. From these observations, we propose that Acala consists of highly variable high-temperature fire fountains and a large area of low-temperature, older flows. Due to these recent outbursts, we expect that any images of Acala obtained by JunoCam will show surface changes from Galileo images.

By combining multiple spacecraft and telescope data sets, the first fully global volcanic heat flow map of Io has been created, incorporating data down to spatial resolutions of ∼10 km pixel ^−1 in Io’s polar regions. Juno Jovian Infrared Auroral Mapper data have filled coverage gaps in Io’s polar regions and other areas poorly imaged by Galileo instruments. A total of 343 thermal sources are identified in data up to mid-2023. While poor correlations are found between the longitudinal distribution of volcanic thermal emission and radially integrated end-member models of internal heating, the best correlations are found with shallow asthenospheric tidal heating and magma ocean models and negative correlations with the deep-mantle heating model. The presence of polar volcanoes supports, but does not necessarily confirm, the presence of a magma ocean on Io. We find that the number of active volcanoes per unit area in polar regions is no different from that at lower latitudes, but we find that Io’s polar volcanoes are smaller, in terms of thermal emission, than those at lower latitudes. Half as much energy is emitted from polar volcanoes as from those at lower latitudes, and the thermal emission from the north polar cap volcanoes is twice that of those in the south polar cap. Apparent dichotomies in terms of volcanic advection and resulting power output exist between sub- and anti-Jovian hemispheres, between polar regions and lower latitudes, and between the north and south polar regions, possibly due to internal asymmetries or variations in lithospheric thickness.

A mission to Jupiter's moon Io, the most volcanically active body in the solar system, was suggested as a priority for the New Frontiers program in the 2013 Planetary Science Decadal Survey. We present a New Frontiers–class mission concept, Vulcan, that was designed as an educational exercise through the Jet Propulsion Laboratory’s 2022 Planetary Science Summer School. Vulcan would leverage an instrument suite consisting of wide- and narrow-angle cameras, a thermal infrared spectrometer, two fluxgate magnetometers, and ion and electron electrostatic analyzers to conduct the most thorough investigation of Io to date. Using 78 flybys over a 2 yr primary science mission, Vulcan would characterize the effects of tidal forces on the differentiation state, crustal structure, and volcanism of Io and investigate potential interactions between Io's volcanoes, surface features, and atmosphere. Although Vulcan was developed as an academic exercise, we show that a New Frontiers–class mission to Io could achieve transformative science in both geophysics and plasma physics, unifying typically disparate subfields of planetary science. A dedicated mission to Io, in combination with the Europa Clipper and Jupiter Icy Moons Explorer missions, would address fundamental questions raised by the 2023 Planetary Science Decadal Survey and could complete our understanding of the spectrum of planetary habitability. Lessons learned from Vulcan could be applied to a New Frontiers 5 Io mission concept in the near future.

Small planetary bodies in the solar system, including Io, Ganymede, and Callisto, may have a crust denser than their underlying mantle. Despite the inherent gravitational instability of such structures, we show that the growth timescale of the Rayleigh–Taylor (RT) instability can be as long as the age of the solar system, owing to the strong temperature dependence of viscosity. Even in cases where the instability timescale is shorter, the instability is confined to a thin layer at the base of the crust, making the foundering of the entire crust improbable in many scenarios. This study delineates the onset and aftermath of the RT instability, applying a quantitative framework to assess the stability of (i) rock-contaminated crust on icy satellites, and (ii) silicate crust floating on top of a subsurface magma ocean on Io. Notably, for Io the RT instability peels off only 10–100 m from the crust’s base, and thermal diffusion rapidly recovers the crustal thickness through solidification of a magma ocean. Despite recurrent delamination of the crustal base, the initial crustal thickness is maintained by thermal diffusion, virtually stabilizing a floating dense crust. Cracking of the crust also is unlikely to result in the foundering of the crust. A dense crust on a small body is therefore difficult to be overturned, suggesting the potential ubiquity of dense surface layers throughout the solar system.

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In this work, we present the most updated catalog of Io hot spots based on Juno/JIRAM data. We find 242 hot spots, including 23 previously undetected. Over the half of the new hot spots identified, are located at high northern and southern latitudes (>70°). We observe a latitudinal variability and a larger concentration of hot spots in the polar regions, in particular in the North. The comparison between JIRAM and the most recent Io hot spot catalogs listing power output (Veeder et al., 2015, https://doi.org/10.1016/j.icarus.2014.07.028; de Kleer, de Pater, et al., 2019, https://doi.org/10.3847/1538-3881/ab2380), shows JIRAM detected 63% and 88% of the total number of hot spots, respectively. Furthermore, JIRAM observed 16 of the 34 faint hot spots previously identified. JIRAM data revealed thermal emission from 5 dark pateræ inferred to be active from color ratio images, thus confirming that these are hot spots. Plain Language Summary: We mapped the hot spot distribution on Io's surface by analyzing the images acquired by the JIRAM instrument onboard the Juno spacecraft. We identified 242 hot spots, including 23 not present in other catalogs. A large number of the new hot spots identified are in the polar regions, specifically in the northern hemisphere. The comparison between our work and the most recent and updated catalog reveals that JIRAM detected 82% of the most powerful hot spots previously identified and half of the intermediate‐power hot spots, thus showing that these are still active. JIRAM detected 16 out of the 34 faint hot spots previously reported. The resolution of JIRAM may not have been sufficient to detect these faint hot spots, or activity might have faded or stopped. Key Points: We produced a new Io hot spot map based on Juno/JIRAM dataWe identified 242 hot spots, including 23 previously undetectedThe latitudinal hot spot distribution is uneven with a larger concentration at the poles [ABSTRACT FROM AUTHOR]