Variability and geologic associations of volcanic activity on Io in 2001–2016

Cantrall, Clayton; Kleer, K. de; Pater, Imke de; Williams, D. A.; Davies, A. G.; Nelson, David M.

doi:10.1016/j.icarus.2018.04.007

Cited by 24 publications

(44 citation statements)

References 41 publications

(47 reference statements)

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“…The detection of new hot spots that were not previously detected by spacecraft is a common occurrence. Adding the data presented here to that summarized by Cantrall et al (2018), there have now been 104 distinct hot spots seen in the AO data from 2001-2018, 25-30 of which were not previously seen by spacecraft. It is likely that many of these hot spots have been active since before the Galileo and Voyager visits but were not emitting sufficient radiation during the visits to have been detected.…”

Section: Discussionmentioning

confidence: 54%

Io’s Volcanic Activity from Time Domain Adaptive Optics Observations: 2013–2018

Kleer

Pater

Molter

et al. 2019

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We present measurements of the near-infrared brightness of Io's hot spots derived from 2-5 µm imaging with adaptive optics on the Keck and Gemini N telescopes. The data were obtained on 271 nights between August 2013 and the end of 2018, and include nearly 1000 detections of over 75 unique hot spots. The 100 observations obtained between 2013 and 2015 have been previously published in de Kleer and de Pater (2016a); the observations since the start of 2016 are presented here for the first time, and the analysis is updated to include the full five-year dataset. These data provide insight into the global properties of Io's volcanism. Several new hot spots and bright eruptions have been detected, and the preference for bright eruptions to occur on Io's trailing hemisphere noted in the 2013-2015 data (de Kleer and de Pater 2016a) is strengthened by the larger dataset and remains unexplained. The program overlapped in time with Sprint-A/EXCEED and Juno observations of the jovian system, and correlations with transient phenomena seen in other components of the system have the potential to inform our understanding of the impact of Io's volcanism on Jupiter and its neutral/plasma environment. 2 de Kleer et al.Volcanoes are also distributed non-randomly across Io's surface, showing in particular a dearth of activity at the sub-and anti-jovian longitudes, as well as in polar regions (Hamilton et al. 2013;Veeder et al. 2015; de Kleer and de Pater 2016b), although no dataset published to date has had good coverage of the high latitudes. The spatial distribution of Io's surface heat flow may place constraints on models for tidal heat dissipation in Io's interior, or may indicate the degree of fluid flow in Io's mantle through the amount of smoothing in the observed spatial trends relative to the expected patterns. Without allowing for lateral movement of melt, the end-member case of heat deposition in a shallow aesthenosphere predicts higher heat flow at lower latitudes with the greatest heat flow centered at the sub-jovian and anti-jovian regions. In contrast, the end-member case of deep mantle heating results in enhanced heat flow at the poles (Gaskell et al., 1988;Segatz et al., 1988).Determining the temporal and spatial distribution of Io's volcanism requires a large sample size of hot spot detections over a range of timescales. We have been building up a database of thermal emission from individual volcanoes on Io's surface since 2013, when we initiated a time domain campaign of adaptive optics imaging of Io's volcanoes at the Keck and Gemini N telescopes. Io has been observed using adaptive optics on Keck since 2001(Marchis et al. 2002, but only since 2013 has there been a dedicated Io observing program at such high cadence. These observations spatially resolve Io, permitting the identification of individual active volcanoes, and are often made at multiple wavelengths in the 2-5 µm range in order to constrain temperature and total power output. The observations have a typical spatial resolution of ∼100-500 km depending o...

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Section: Discussionmentioning

confidence: 54%

Io’s Volcanic Activity from Time Domain Adaptive Optics Observations: 2013–2018

Kleer

Pater

Molter

et al. 2019

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“…For the high-resolution datasets, the spectral coverage lacks sufficient baseline regions, and the thermal emission is left as a free parameter in the fits to the gas emission band. The thermal emission is modeled with a Planck function at a single temperature and emitting area (T th , A th ); this simple parameterization provides a good fit to the data, and the resultant temperatures fall within the range seen in previous observations with larger spectral coverage (∼500-1000 K; de Pater et al 2002;Laver et al 2007), as well as with the temperature estimated for December 25, 2015 from the OSIRIS dataset (de Pater et al 2018).…”

Section: Thermal Continuummentioning

confidence: 66%

“…On UT December 25, 2015 we observed Io with both Keck telescopes simultaneously, using the NIRSPEC spectrograph in high-resolution mode (R∼25,000) on Keck II (McLean et al 1998) and the OSIRIS integral-field spectrograph with adaptive optics on Keck I (Larkin et al 2006), for which the grating was upgraded in 2013 (Mieda et al 2014). The latter observations were presented by de Pater et al (2017b) and described in detail in de Pater et al (2018). The sky was clear during the observations but seeing was variable, in particular during the standard star observations.…”

Section: December 25 2015mentioning

confidence: 85%

Emission from volcanic SO gas on Io at high spectral resolution

Kleer

Pater

Ádámkovics

2019

Icarus

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Jupiter's moon Io hosts a dynamic atmosphere that is continually stripped off and replenished through frost sublimation and volcanic outgassing. We observed an emission band at 1.707 µm thought to be produced by hot SO molecules directly ejected from a volcanic vent; the observations were made the NIRSPEC instrument on the Keck II telescope while Io was in eclipse by Jupiter on three nights in 2012-2016, and included two observations with 10× higher spectral resolution than all prior observations of this band. These high-resolution spectra permit more complex and realistic modeling, and reveal a contribution to the SO emission from gas reservoirs at both high and low rotational temperatures. The scenario preferred by de Pater et al. (2002) for the source of the SO gas -direct volcanic emission of SO in the excited state -is consistent with these two temperature components if the local gas density is high enough that rotational energy can be lost collisionally before the excited electronic state spontaneously decays. Under this scenario, the required bulk atmospheric gas density and surface pressure are n ∼ 10 11 cm −3 and 1-3 nbar, consistent with observations and modeling of Io's dayside atmosphere at altitudes below 10 km (Lellouch et al. 2007; Walker et al. 2010). These densities and pressures would be too high for the nightside density if the atmospheric density drops by an order of magnitude or more at night (as predicted by sublimation-supported models), but recent results have shown a drop in SO 2 gas density of only a factor of 5±2 (Tsang et al. 2016). While our observations taken immediately post-ingress and pre-egress (on different dates) prefer models with only a factor of 1.5 change in gas density, a factor of 5 change is still well within uncertainties. In addition, our derived gas densities are for the total bulk atmosphere, while Tsang et al. (2016) specifically measured SO 2 . The low-temperature gas component is warmer for observations in the first 20 minutes of eclipse (in Dec 2015) than after Io had been in shadow for 1.5 hours (in May 2016), suggesting cooling of the atmosphere during eclipse. However, individual spectra during the first ∼30 minutes of eclipse do not show a systematic cooling, indicating that such a cooling would have to take place on a longer timescale than the ∼10 minutes for cooling of the surface (Tsang et al. 2016). Excess emission is consistently observed at 1.69 µm, which cannot be matched by two-temperature gas models but can be matched by models that over-populate high rotational states. However, a detailed assessment of disequilibrium conditions will require high-resolution spectra that cover both the center of the band and the wing at 1.69 µm. Finally, a comparison of the total band strengths observed across eight dates from 1999-2016 reveals no significant dependence on thermal hot spot activity (including Loki Patera), on the time since Io has been in shadow, nor on the phase of Io's orbit at the time of observation.

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“…We assume that deviations from spherical symmetry are secondary effects imprinted on a leading-order radial structure. These deviations from spherical symmetry are expected to be important in discerning the global distribution of tidal dissipation (Cantrall et al, 2018;de Kleer & de Pater, 2016;Rathbun et al, 2018;Veeder et al, 2012) but are beyond the scope of this work. Tidal dissipation models that match Io's surface heat flux utilize either very low viscosities (Steinke et al, 2020) or empirically parameterized rheologies (Bierson & Nimmo, 2016;Renaud & Henning, 2018).…”

Section: Journal Of Geophysical Research: Planetsmentioning

confidence: 99%

Magmatic Intrusions Control Io's Crustal Thickness

2020

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Io, the most volcanically active body in the solar system, loses heat through eruptions of hot lava. Heat is supplied by tidal dissipation and is thought to be transferred through the mantle by magmatic segregation, a mode of transport that sets it apart from convecting terrestrial planets. We present a model that couples magmatic transport of tidal heat to the volcanic system in the crust, in order to determine the controls on crustal thickness, magmatic intrusions, and eruption rates. We demonstrate that magmatic intrusions are a key component of Io's crustal heat balance; around 80% of the magma delivered to the base of the crust must be emplaced and frozen as plutons to match rough estimates of crustal thickness. As magma ascends from a partially molten mantle into the crust, a decompacting boundary layer forms, which can explain possible observations of a high‐melt‐fraction region.

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Variability and geologic associations of volcanic activity on Io in 2001–2016

Cited by 24 publications

References 41 publications

Io’s Volcanic Activity from Time Domain Adaptive Optics Observations: 2013–2018

Io’s Volcanic Activity from Time Domain Adaptive Optics Observations: 2013–2018

Emission from volcanic SO gas on Io at high spectral resolution

Magmatic Intrusions Control Io's Crustal Thickness

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