global near ir maps from gemini n and keck in 2010 with a special focus on janus patera and kanehekili fluctus abstract we have imaged io in the near infrared 1 5 m with adaptive optics on the 10 m w m keck ii and the gemini north telescopes we have constructed global maps from the data taken in 2010 although numerous hot spots are visible the maps are dominated by two volcanic centers loki patera and kanehekili fluctus we have examined in detail the thermal emission from janus patera and kanehekili fluctus using images obtained between 2003 and 2010 and have created a timeline of volcanic activity at these locations utilizing data from a wide variety of sources based on our data and this timeline we find that the thermal emission from janus patera is relatively steady indicative of an active lava lake the thermal emission from kanehekili fluctus however is quite variable and is indicative of the emplacement of extensive lava flows in 2010 the thermal emission from this location was 10 times higher than ever seen before indicative of a particularly voluminous eruption of lava

lava lakes on io new perspectives from modeling abstract loki patera 310 w 12 n is io s largest patera at 180 km in diameter its morphology and distinct thermal behavior have led researchers to hypothesize that loki patera may either be an active lava lake that experiences periodic overturn or a shallow depression whose floor is episodically resurfaced with thin flows using results from mathematical models we suggest that a better model for loki s behavior is the terrestrial superfast spreading east pacific rise epr near 17 30 south we propose that like at the southern epr loki patera is underlain by a thin persistent magma lens that feeds thin temporary lava lakes within the patera also like the southern epr overspilling of the volcanic depression is rare with most of the lava volume being emplaced via a subsurface network of lava tubes

new estimates for io eruption temperatures implications for the interior abstract the initial interpretation of galileo data from jupiter s moon io suggested eruption temperatures 1600 c tidal heating models have difficulties explaining io s prodigious heat flow if the mantle is 1300 c although we suggest that temperatures up to 1450 c may be possible in general io eruption temperatures have been overestimated because the incorrect thermal model has been applied much of the thermal emission from high temperature hot spots comes from lava fountains but lava flow models were utilized we apply a new lava fountain model to the highest reported eruption temperature the ssi observation of the 1997 eruption at pillan this resets the lower temperature limit for the eruption from 1600 to 1340 c additionally viscous heating of the magma may have increased eruption temperature by 50 100 c as a result of the strong compressive stresses in the ionian lithosphere while further work is needed it appears that the discrepancy between observations and interior models is largely resolved

keck ao observations of io in and out of eclipse abstract we present adaptive optics ao observations of io taken with the w m keck ii telescope on 18 december 2001 ut before the satellite went into eclipse and while it was in jupiter s shadow making these kind of io in eclipse observations as well as the associated data reduction and analysis are challenging hence one focus of the paper is to explain the methods and tools used for these data sets for the sunlit images io itself was used as the wavefront reference source while nearby ganymede was used as reference star when io was in eclipse observations were obtained in k l and m bands the sunlit images have been deconvolved using mistral the io in eclipse data were deconvolved with idac and mistral the former gives better results both in absolute photometry and in matching the original images we determined the flux densities of the hot spots from the original io in eclipse data with starfinder as well as from the deconvolved images by integrating the intensity over the relevant areas we determined the highly anisoplanatic psf via a fft method from the original data and used this in starfinder and as a starting psf for idac and mistral we derived temperatures and areal coverage of all 19 spots detected in both k and l band images of io in eclipse we also determined temperatures and areal coverage of the hot spots visible on the l and m band images of sunlit io most volcanoes contain a compact hot core 10 km2 at 600 800 k within a larger area at lower temperatures e g 102 104 km2 at 300 500 k the total heat flow contributed by these active volcanoes is 0 2 w m 2 8 of the average global heat flow measured at 5 20 m by veeder et al j geophys res 99 1994 17095

assessment and estimation of groundwater recharge for a catchment located in highland tropical climate in central ethiopia using catchment soil water balance swb and chloride mass balance cmb techniques two commonly applied groundwater recharge estimation techniques namely soil water balance swb and the chloride mass balance cmb methods were applied and compared to quantify and analyse groundwater recharge in the akaki catchment located in central ethiopia the semi distributed swb method estimated natural groundwater recharge at 105 mm a 10 of the mean annual areal precipitation maap the chloride mass balance method applied to the same catchment estimated mean annual groundwater recharge at 273 mm a 25 of the maap the swb recharge value is much less than the recharge estimated by cmb method highlighting the importance of preferential flow path recharge mechanism which is not captured by the swb method in situ permeability measurements undertaken as part of this research and an earlier investigation based on environmental isotopes have demonstrated that the catchment gets recharged both from direct and preferential flow recharge mechanisms which explains the discrepancy between recharge estimated through the two methods therefore swb model result which only takes into consideration the piston type flow recharge mechanism should be taken as the minimum possible groundwater recharge for the catchment characterized by fractured aquifers the mean recharge estimate from the two methods represents the maximum possible recharge estimate for the catchment investigated although calibration of the recharge estimates was not possible the swb recharge estimate is found to be highly sensitive to changes in precipitation input the findings of this research underline the fact that multiple recharge estimation methods are important to understand and capture possible recharge mechanisms and to reach to an acceptable recharge estimate

the thermal signature of volcanic eruptions on io and earth abstract we investigate a spectrum based technique to identify the style of active volcanic eruptions on jupiter s moon io thermal remote sensing of io has had to rely primarily on low spatial resolution data similar to low spatial resolution satellite data applied to detecting and charting the temporal evolution of terrestrial hot spots these terrestrial analyses use data from sensors designed to monitor the weather and sea surface temperature on io such low spatial resolution data are used to classify eruption styles modes of emplacement by means of several criteria related to the temporal evolution of the infrared spectrum associated with the eruptive activity at each hot spot which we term thermal signature we find that the ratio of the emission at 2 and 5 m and how this ratio changes with time is often diagnostic of eruption style even in low spatial resolution data tests using thermal data for terrestrial ground truth cases show that our classification system is valid on earth the results of our analysis can be used to aid in the design of future space based instruments that can be used for volcano monitoring on io as well as earth

io volcanism seen by new horizons a major eruption of the tvashtar volcano jupiter s moon io is known to host active volcanoes in february and march 2007 the new horizons spacecraft obtained a global snapshot of io s volcanism a 350 kilometer high volcanic plume was seen to emanate from the tvashtar volcano 62 n 122 w and its motion was observed the plume s morphology and dynamics support nonballistic models of large io plumes and also suggest that most visible plume particles condensed within the plume rather than being ejected from the source in images taken in jupiter eclipse nonthermal visible wavelength emission was seen from individual volcanoes near io s sub jupiter and anti jupiter points near infrared emission from the brightest volcanoes indicates minimum magma temperatures in the 1150 to 1335 kelvin range consistent with basaltic composition

tidal dissipation surface heat flow and figure of viscoelastic models of io abstract the distribution of hot spots on io s surface and io s figure constrain models of io s interior voyager observations indicate that most hot spots and volcanic plumes are close to the equator recently however it has been proposed that a large low albedo feature in the south polar region may be the source of 40 of the surface heat flow we calculate spatial distributions of the dissipation rate surface heat flow and the figures of three and four layer maxwell rheology models of io by using the correspondence principle the models are required to satisfy the observed surface heat flow constraint and are consistent with the composition of a dehydrated c2 chondrite they consist of an inviscid fe fes core and viscoelastic silicate mantle and lithosphere layers a comparison of the calculated equilibrium figure with the observed figure of io supports the chosen core radius of 980 km in addition the four layer model has a partially molten asthenosphere a few tens of kilometers thick the preferred three layer model has a mantle shear modulus of 10 10 pa and a viscosity of 2 10 16 pa s consistent with rock properties the tidal dissipation rate for this model is largest along the polar axis integration of the dissipation rate over radius gives a surface heat flow with maxima at the poles and minima near the sub jovian and anti jovian points in contrast the dissipation rate in a molten or partially molten incompressible asthenosphere has maxima near the equator and is close to zero at the poles the asthenosphere dissipation rate is mainly a function of asthenosphere viscosity and thickness the thinner the asthenosphere the smaller is the required viscosity a 50 km thick asthenosphere requires a viscosity of about 10 8 pa s a strong south polar hot spot if it can be confirmed by infrared observation favors dissipation in the mantle but does not exclude dissipation in a partially molten asthenosphere equatorial hot spots and the concentration of prometheus type plumes near the equator favor asthenosphere heating but do not rule out deep mantle dissipation both asthenosphere and deep mantle heating may contribute to io s surface heat flow the properties of magma transport through the lithosphere and the planform of mantle convection might exert a control on the surface expression of heating at greater depth

internal structure of io and the global distribution of its topography abstract the distribution of equatorial long wavelength topography on io consists of alternating basins and swells similar to the pattern expected if tidal heating in a thin asthenosphere controls the elevation of the surface through a conductive lithosphere in isostatic equilibrium the equatorial basin swell pattern is shifted in longitude with respect to theoretical tidal heating patterns however making the correlation between theoretical heat flow and elevation unclear we calculate global topography for multilayer io models with dissipation occurring in a viscous asthenosphere and a solid mantle two models are considered a thermal swell model in which topography and heat flow are positively correlated and a differentiated lithosphere model in which topography and heat flow are negatively correlated both models match the observed pattern of alternating basins and swells along the equator and moderate polar topography if about two thirds of the tidal heating occurs in the asthenosphere and about one third occurs in the underlying solid mantle the mean thicknesses of the model lithospheres are 35 km in the differentiated model and 150 km in the thermal swell model polar topography and the hypsometric distribution of elevations in the differentiated lithosphere model match the observations better than the thermal swell model in a differentiated lithosphere model consistent with the topography the asthenosphere is at least 50 km thick with viscosity about 100 mpa sec and is about 7 more dense than the lithosphere the mantle density exceeds the asthenosphere density by at least 10 the shift of the equatorial basin swell pattern suggests that io s lithosphere has recently undergone a zonal rotation of about 25

depositional frequency of german subfossil oaks climatically and non climatically induced fluctuations in the holocene a highly resolved record of the depositional frequency of subfossil trees since 8263 bc in the valley of the river main is presented different aspects of forest dynamics are explored including depositional anomal ies phases of low or zero departures changes in forest density based on tree growth trend classes gtcs and regeneration using mean lifespan ml data this reveals a number of climatically induced environmental changes that are synchronous with events in the north atlantic region and therefore may reflect a facet of the north atlantic climate system three periods are recognized 1 pre 3500 bc when depositional frequency was dominated by climatic events with notable anomalies at 6200 and 4100 bc 2 between 3500 and 1200 bc when climatically triggered events were enhanced by forest clearances especially marked anomalies occurring around 2700 2300 and 1700 bc and 3 post 1200 bc when the climatic information is obscured by human activities

io loki patera as a magma sea 1 we develop a physical model for loki patera as a magma sea we calculate the total volume of magma moving through the loki patera volcanic system every resurfacing cycle 540 days and the resulting variation in thermal emission the rate of magma solidification at times reaches 3 106 kg s 1 with a total solidified volume averaging 100 km3 yr 1 a simulation of gas physical chemistry evolution yields the crust porosity profile and the timescale when it will become dense enough to founder in a manner consistent with observations the loki patera surface temperature distribution shows that different areas are at different life cycle stages on a regional scale however there can be coordinated activity indicated by the wave of thermal change which progresses from loki patera s sw quadrant toward the ne at a rate of 1 km d 1 using the observed surface temperature distribution we test several mechanisms for resurfacing loki patera finding that resurfacing with lava flows is not realistic only the crustal foundering process is consistent with observations these tests also discovered that sinking crust has a heat deficit which promotes the solidification of additional magma onto the sinking plate bulking up in the limiting case the mass of sinking material can increase to a mass of 3 times that of the foundering plate with all this solid matter sinking there is a compensating upward motion in the liquid magma this can be in excess of 2 m yr 1 in this manner solid liquid convection is occurring in the sea

evidence of a global magma ocean in io s interior extensive volcanism and high temperature lavas hint at a global magma reservoir in io but no direct evidence has been available we exploited jupiter s rotating magnetic field as a sounding signal and show that the magnetometer data collected by the galileo spacecraft near io provide evidence of electromagnetic induction from a global conducting layer we demonstrate that a completely solid mantle provides insufficient response to explain the magnetometer observations but a global subsurface magma layer with a thickness of over 50 kilometers and a rock melt fraction of 20 or more is fully consistent with the observations we also place a stronger upper limit of about 110 nanoteslas surface equatorial field on the dynamo dipolar field generated inside io

two new rare high effusion outburst eruptions at rarog and heno paterae on io observations obtained with the near infrared camera nirc2 coupled to the adaptive optics system on the 10 m w m keck ii telescope on mauna kea hawaii on 15 august 2013 at 15 30 ut revealed two large outburst class volcanic eruptions on io follow up observations five days later showed that both eruptions had substantially faded the most energetic eruption was at rarog patera at a location near 305 w 42 s a smaller one occurred further south at 310 w and 57 s close to heno patera total radiant fluxes at rarog patera on august 15 were of order 500 gw sr m at wavelengths between 2 and 4 m and close to 250 gw sr m at 1 6 m indicative of an effective temperature of 1040 k over an area of 120 km 2 and a total thermal emission of nearly 8 tw at heno patera the 4 m flux measured 250 gw sr m and 90 gw sr m at 2 2 m suggestive of an effective temperature of 720 k over an area of more than 300 km 2 and a total thermal emission of 5 6 tw fits of the davies davies a g 1996 icarus 124 1 45 61 io flow model indicate that these two eruptions are vigorous and the exposed surfaces are mostly very young no older than 4 5 min at rarog patera and a few hours at heno patera the model fits suggest that in both locations lava fountaining is taking place a highly energetic style of volcanism using follow up observations taken between august 20 and september 7 we estimate peak effusion rates between 5 10 4 and 10 5 m 3 s

near infrared monitoring of io and detection of a violent outburst on 29 august 2013 abstract we present initial data from our campaign to monitor io in the near infrared beginning in august 2013 using 3 8 m adaptive optics imaging at gemini n and 2 5 m disk integrated spectroscopy at nasa s irtf conducted during 2013 2014 these observations are coincident with the isas jaxa exceed mission s continuous monitoring of the io plasma torus and will enable the speculated effects of volcanic outgassing on the torus to be observed directly in addition to enabling an assessment of the frequency and properties of large scale outbursts on 29 august 2013 we detected a powerful eruption designated 201308c on io at 223 5 2 6 w 29 1 1 8 n emitting between 15 and 25 tw this event is one of the most powerful eruptions ever seen on io and falls into the rare outburst class this was the third eruption of this type seen on io in august 2013 an unprecedented occurrence also unprecedented was the charting of the decay in thermal emission over the subsequent days and weeks modeling of the outburst spectrum places a lower bound of 1200 1300 k on the eruption temperature and is suggestive of temperatures 1900 k or higher typically associated with ultramafic lava composition the eruption is likely a highly energetic high volume lava fountain event

the heartbeat of the volcano the discovery of episodic activity at prometheus on io the temporal signature of thermal emission from a volcano is a valuable clue to the processes taking place both at and beneath the surface the galileo near infrared mapping spectrometer nims observed the volcano prometheus on the jovian moon io on multiple occasions between 1996 and 2002 the 5 micron m brightness of this volcano shows considerable variation from orbit to orbit prometheus exhibits increases in thermal emission that indicate episodic though non periodic effusive activity in a manner akin to the current pu u o o kupaianaha afterwards referred to as the pu u o o eruption of kilauea hawai i the volume of material erupted during one prometheus eruption episode defined as the interval from minimum thermal emission to peak and back to minimum from 6 november 1996 to 7 may 1997 is estimated to be 0 8 km3 with a peak instantaneous volumetric flux effusion rate of 140 m3 s 1 and an averaged volumetric flux eruption rate of 49 m3 s 1 these quantities are used to model subsurface structure magma storage and magma supply mechanisms and likely magma chamber depth prometheus appears to be supplied by magma from a relatively shallow magma chamber with a roof at a minimum depth of 2 3 km and a maximum depth of 14 km this is a much shallower depth range than sources of supply proposed for explosive possibly ultramafic eruptions at pillan and tvashtar as prometheus type effusive activity is widespread on io shallow magma chambers containing magma of basaltic or near basaltic composition and density may be common this analysis strengthens the analogy between prometheus and pu u o o at least in terms of eruption style even though the style of eruption appears to be similar effusive emplacement of thin insulated compound pahoehoe flows the scale of activity at prometheus greatly exceeds current activity at pu u o o in terms of volume erupted area covered and magma flux whereas the estimated magma chamber at prometheus dwarfs the pu u o o magma chamber it fits within expectations if the pu u o o chamber were scaled for the greater volumetric flux and lower gravity of io recent volumetric eruption rates derived from galileo data for prometheus were considerably smaller than the rate that produced the extensive flows formed in the 17 years between the voyager and galileo missions these smaller eruption rates coupled with the fact that flows are not expanding laterally may mean that the immediate heat source that generates the prometheus plume is simultaneously running out of available volatiles and the thermal energy that drives mobilization of volatiles this raises the question of whether the current prometheus eruption is in its last throes

high temperature hot spots on io as seen by the galileo solid state imaging ssi experiment high temperature hot spots on io have been imaged at 50 km spatial resolution by galileo s ccd imaging system ssi images were acquired during eclipses io in jupiter s shadow via the ssi clear filter 0 4 1 0 m detecting emissions from both small intense hot spots and diffuse extended glows associated with io s atmosphere and plumes a total of 13 hot spots have been detected over 70 of io s surface each hot spot falls precisely on a low albedo feature corresponding to a caldera floor and or lava flow the hot spot temperatures must exceed 700 k for detection by ssi observations at wavelengths longer than those available to ssi require that most of these hot spots actually have significantly higher temperatures 1000 k or higher and cover small areas the high temperature hot spots probably mark the locations of active silicate volcanism supporting suggestions that the eruption and near surface movement of silicate magma drives the heat flow and volcanic activity of io

active volcanism on io as seen by galileo ssi abstract active volcanism on io has been monitored during the nominal galileo satellite tour from mid 1996 through late 1997 the solid state imaging ssi experiment was able to observe many manifestations of this active volcanism including 1 changes in the color and albedo of the surface 2 active airborne plumes and 3 glowing vents seen in eclipse about 30 large scale tens of kilometers surface changes are obvious from comparison of the ssi images to those acquired by voyager in 1979 these include new pyroclastic deposits of several colors bright and dark flows and caldera floor materials there have also been significant surface changes on io during the galileo mission itself such as a new 400 km diameter dark pyroclastic deposit around pillan patera while these surface changes are impressive the number of large scale changes observed in the four months between the voyager 1 and voyager 2 flybys in 1979 suggested that over 17 years the cumulative changes would have been much more impressive there are two reasons why this was not actually the case first it appears that the most widespread plume deposits are ephemeral and seem to disappear within a few years second it appears that a large fraction of the volcanic activity is confined to repeated resurfacing of dark calderas and flow fields that cover only a few percent of io s surface the plume monitoring has revealed 10 active plumes comparable to the 9 plumes observed by voyager one of these plumes was visible only in the first orbit and three became active in the later orbits only the prometheus plume has been consistently active and easy to detect observations of the pele plume have been particularly intriguing since it was detected only once by ssi despite repeated attempts but has been detected several times by the hubble space telescope at 255 nm pele s plume is much taller 460 km than during voyager 1 300 km and much fainter at visible wavelengths prometheus type plumes 50 150 km high long lived associated with high temperature hot spots may result from silicate lava flows or shallow intrusions interacting with near surface so2 a major and surprising result is that 30 of io s volcanic vents glow in the dark at the short wavelengths of ssi these are probably due to thermal emission from surfaces hotter than 700 k with most hotter than 1000 k well above the temperature of pure sulfur volcanism active silicate volcanism appears ubiquitous there are also widespread diffuse glows seen in eclipse related to the interaction of energetic particles with the atmosphere these diffuse glows are closely associated with the most active volcanic vents supporting suggestions that io s atmopshere is dominated by volcanic outgassing globally volcanic centers are rather evenly distributed however 14 of the 15 active plumes seen by voyager and or galileo are within 30 of the equator and there are concentrations of glows seen in eclipse at both the sub and antijovian points these patterns might be related to asthenospheric tidal heating or tidal stresses io will continue to be observed during the galileo europa mission which will climax with two close flybys of io in late 1999

ground based observations of time variability in multiple active volcanoes on io abstract since before the beginning of the galileo spacecraft s jupiter orbital tour we have observed io from the ground using nasa s infrared telescope facility irtf we obtained images of io in reflected sunlight and in eclipse at 2 3 3 5 and 4 8 m in addition we have measured the 3 5 m brightness of an eclipsed io as it is occulted by jupiter these lightcurves enable us to measure the brightness and one dimensional location of active volcanoes on the surface during the galileo era two volcanoes were observed to be regularly active loki and either kanehekili and or janus at least 12 other active volcanoes were observed for shorter periods of time including one distinguishable in images that include reflected sunlight these data can be used to compare volcano types and test volcano eruption models such as the lava lake model for loki

volcanic history geologic analysis and map of the prometheus patera region on io data from jupiter s moon io returned by the galileo spacecraft have been used to create a geologic map of prometheus patera its associated flow field and nearby features we have identified the location of the vent that fed the prometheus flow field during the galileo epoch in the north eastern portion of the main prometheus flow field this vent is the probable source of a small sulphur rich plume previous studies suggested that the vent may be atop a tectonic fault but we find that the vent is offset from the putative fault it is plausible that in the past magma exploited the fault to reach the surface at prometheus patera but subsequent magma cooling in the conduit could have caused an obstruction preventing further eruptions from providing significant contributions to the prometheus flow field we also speculate on how a new prometheus plumbing system may be fed by mafic magmas after melt stalls in magma reservoirs during its ascent through the lithosphere from the mantle

silicate volcanism on io io is currently emitting 1 1 5 w m 2 of tidal energy as a result of its volcanic activity if the lithosphere is more than 20 km thick as appears probable from the surface relief only a fraction of the tidal energy can be dissipated within the lithosphere otherwise it will become thinner the rest of the tidal energy must be dissipated below the lithosphere io is likely to be highly differentiated as a result of the volcanic activity with a low melting temperature fraction such as basalt near the surface and a high melting temperature fraction such as peridotite at depth if solidus temperatures are reached at depths shallower than the thickness of the basalt layer a partial melt zone will separate an all basalt lithosphere above from a peridotite mantle below and part of the tidal energy will be dissipated by viscous deformation within the melt zone most of the energy dissipated below the lithosphere will be transported upward through the lithosphere as silicate magma which is generated in quantities sufficient to resurface the satellite at a rate of a few tenths of a centimeter a year depending on the lithosphere thickness many of the characteristics of the ionian surface have been explained in terms of sulfur volcanism however most of the features observed can be as readily explained by silicate volcanism and silicates are more consistent with the apparent strength of the surface as implied by the relief simulations of basaltic eruptions indicate that the surface temperatures that would result from basaltic eruptions are similar to those measured by the voyager infrared interferometer spectrometer experiment the high rates of emission by the ionian hot spots imply eruption rates that are high compared with typical terrestrial eruptions an eruption rate of 4000 m3 s 1 may be required to explain loki which is currently emitting 1013 w although the near surface materials are mainly silicate they may contain several percent of volatile components rich in s na and k remobilization of these components by the ongoing silicate eruptions causes the plumes provides material to the torus and gives the satellite its characteristic reflectivity

charting thermal emission variability at pele janus patera and kanehekili fluctus with the galileo nims io thermal emission database nited abstract using the nims io thermal emission database nited a collection of over 1000 measurements of radiant flux from io s volcanoes davies a g et al 2012 geophys res lett 39 l01201 doi 10 1029 2011gl049999 we have examined the variability of thermal emission from three of io s volcanoes pele janus patera and kanehekili fluctus at pele the 5 m thermal emission as derived from 28 night time observations is remarkably steady at 37 10 gw m 1 re affirming previous analyses that suggested that pele an active rapidly overturning silicate lava lake janus patera also exhibits relatively steady 5 m thermal emission 20 3 gw m 1 in the four observations where janus is resolved from nearby kanehekili fluctus janus patera might contain a pele like lava lake with an effusion rate qf of 40 70 m3 s 1 it should be a prime target for a future mission to io in order to obtain data to determine lava eruption temperature kanehekili fluctus has a thermal emission spectrum that is indicative of the emplacement of lava flows with insulated crusts effusion rate at kanehekili fluctus dropped by an order of magnitude from 95 m3 s 1 in mid 1997 to 4 m3 s 1 in late 2001

the geothermal gradient of io consequences for lithosphere structure and volcanic eruptive activity we solve numerically the equations describing the transfer of heat through the lithosphere of io by a mixture of conduction and volcanic advection as proposed by o reilly and davies o reilly t c davies g f 1981 geophys res lett 8 313 316 removing the requirement that average material properties must be used as expected the dominance of advective heat transfer by volcanic eruptions means that io s geothermal gradient well away from volcanic centres is very small of order 1 k km 1 this result is independent of any reasonable assumptions about the radiogenic heating rate in the lithosphere the lithosphere temperature does not increase greatly above the surface temperature until the base of the lithosphere is approached except in limited areas around shallow magma bodies as a consequence solid volatile sulphur compounds mobilized by volcanic processes and re deposited on the surface of io commonly remain solid until they reach great depths as they are progressively buried by ongoing activity for current estimates of the volcanic heat transfer rate melting of so2 does not begin until a depth of 20 km and sulphur remains solid to a depth of 26 km in a 30 km thick lithosphere rising magmas can incorporate fluids from these deep sulphur compound aquifers and we quantify the major influence that this can have on the bulk density of the magma and hence the resulting possible intrusion and eruption styles

speckle imaging of volcanic hotspots on io with the keck telescope abstract using speckle imaging techniques on the 10 m w m keck i telescope we observed near infrared emission at 2 2 m from volcanic hotspots on io in july august 1998 using several hundreds of short exposure images we reconstructed diffraction limited images of io on each of three nights we measured the positions of individual hotspots to 0 004 or better corresponding to a relative positional error of 20 km on io s surface the sensitivity of normal ground based images of io is limited by confusion between overlapping sources by resolving these multiple points we detected up to 17 distinct hotspots the largest number ever seen in a single image during the month long span of our 1998 observations several events occurred loki was at the end of a long brightening and we observed it to fade in flux by a factor of 2 8 over the course of one month at the 3 sigma level we see evidence that loki s position shifts by 100 km this suggests that the brightening may not have been located at the primary loki emission center but at a different source within the loki caldera we also see a bright transient source near loki among many other sources we detect a dim source on the limb of io at the latitude of pele this source is consistent with 2 7 of the thermal emission from the pele volcano complex being scattered by the pele plume which would be the first detection of a plume through scattered infrared hotspot emission

io heat flow from dark paterae abstract dark paterae on the jovian satellite io are evidence of recent volcanic activity some paterae appear to be entirely filled with dark volcanic material while others have only partially darkened floors dark paterae have area and heat flow longitudinal distributions that are bimodal as well as anti correlated with the longitudinal distribution of mountains on io at a global scale as part of our study of io s total heat flow we have examined the darkest paterae and quantified their thermal emission in order to assess their contribution this is the first time that the areas of the dark material in these paterae have been measured with such precision and correlated with their thermal emission dark paterae yield a significantly larger contribution to io s heat flow than dark volcanic fields dark paterae including loki patera yield at least 4 10 13 w or 40 of io s total heat flow in comparison dark flow fields yield 10 13 w or 10 of io s total heat flow of the total heat loss from dark paterae loki patera alone yields 10 13 w or 10 of io s total thermal emission

paterae on io a new type of volcanic caldera paterae defined by the international astronomical union as irregular crater s or complex one s with scalloped edges are some of the most prominent topographic features on io paterae on io are unique yet in some aspects they resemble calderas known and studied on earth mars and venus they have steep walls flat floors and arcuate margins and sometimes exhibit nesting all typical of terrestrial and martian basalt shield calderas however they are much larger many are irregular in shape and they typically lack shields their great sizes some 200 km diameter and lack of associated volcanic edifices beg comparison with terrestrial ash flow calderas however there is no convincing evidence on io for the high silica erupted products or dome resurgence associated with this type of caldera ionian paterae seem to be linked with the eruption of large amounts of mafic to ultramafic lavas and colorful sulfur rich materials that cover the floors and sometimes flow great distances away from patera margins they are often angular in shape or are found adjacent to mountains or plateaus indicating tectonic influences on their formation a database of 417 paterae on io measured from images with 3 2 km pixel 1 resolution 80 of its surface reveals that their mean diameter of 41 0 km is close to that for calderas of mars 47 7 km is smaller than that for venus 68 km but dwarfs those for terrestrial basalt shield calderas 6 6 km and ash flow calderas 18 7 km thirteen percent of all paterae are found adjacent to mountains 42 have straight or irregular margins and 8 are found atop low shields abundant smaller paterae with more continuously active lava eruptions are found between 25 s and 25 n latitude whereas fewer and larger paterae are found poleward of these latitudes patera distribution shows peaks at 330 w and 150 w longitude likely related to the direction of greatest tidal massaging by jupiter ionian patera formation may be explained by portions or combinations of models considered for formation of terrestrial calderas yet their unusual characteristics may require new models with a greater role for tectonic processes

volcanism on io estimation of eruption parameters from galileo nims data 1 galileo near infrared mapping spectrometer nims data of volcanic thermal emission are analyzed to determine the power output of a number of ionian volcanoes from which are calculated volumetric eruption rates a two temperature model is used to determine surface temperatures and power output portions of prometheus and six other volcanoes are found to be in excess of 1100 k areas of prometheus are at temperatures close to 1500 k these are minimum eruption temperatures and are consistent with basaltic silicate volcanism for the 14 volcanoes in g1innspec01 volumetric eruption rates e are constrained between 3 and 300 m3 s for basaltic and ultramafic compositions actual e values lie between these limits the small crack fractions hot area to warm area ratio implied from these fits are indicative of a relatively quiescent eruption style such as the emplacement of a pahoehoe or a a flow field the volumetric eruption rates derived from the nims data are greater than those observed in similar styles of volcanism on earth it is apparent that for similar eruption styles the areal extent of activity is greater on io than on earth derived flow thicknesses range from 0 1 to 13 m

io in the near infrared near infrared mapping spectrometer nims results from the galileo flybys in 1999 and 2000 galileo s near infrared mapping spectrometer nims observed io during the spacecraft s three flybys in october 1999 november 1999 and february 2000 the observations which are summarized here were used to map the detailed thermal structure of active volcanic regions and the surface distribution of so2 and to investigate the origin of a yet unidentified compound showing an absorption feature at 1 m we present a summary of the observations and results focusing on the distribution of thermal emission and of so2 deposits we find high eruption temperatures consistent with ultramafic volcanism at pele such temperatures may be present at other hot spots but the hottest areas may be too small for those temperatures to be detected at the spatial resolution of our observations loki is the site of frequent eruptions and the low thermal emission may represent lavas cooling on the caldera s surface or the cooling crust of a lava lake high resolution spectral observations of emakong caldera show thermal emission and so2 within the same pixels implying that patches of so2 frost and patches of cooling lavas or sulfur flows are present within a few kilometers from one another thermal maps of prometheus and amirani show that these two hot spots are characterized by long lava flows the thermal profiles of flows at both locations are consistent with insulated flows with the amirani flow field having more breakouts of fresh lava along its length prometheus and amirani each show a white ring at visible wavelengths while so2 distribution maps show that the highest concentration of so2 in both ring deposits lies outside the white portion visible measurements at high phase angles show that the white deposit around prometheus extends into the so2 ring this suggests that the deposits are thin and that compositional or grain size variations may occur in the radial direction so2 mapping of the chaac region shows that the interior of a caldera adjacent to chaac has almost pure so2 the deposit appears to be topographically controlled suggesting a possible origin by liquid flow

thermal signature eruption style and eruption evolution at pele and pillan on io the galileo spacecraft has been periodically monitoring volcanic activity on io since june 1996 making it possible to chart the evolution of individual eruptions we present results of coanalysis of near infrared mapping spectrometer nims and solid state imaging ssi data of eruptions at pele and pillan especially from a particularly illuminating data set consisting of mutually constraining near simultaneous nims and ssi observations obtained during orbit c9 in june 1997 the observed thermal signature from each hot spot and the way in which the thermal signature changes with time tightly constrains the possible styles of eruption pele and pillan have very different eruption styles from september 1996 through may 1999 pele demonstrates an almost constant total thermal output with thermal emission spectra indicative of a long lived active lava lake the nims pillan data exhibit the thermal signature of a pillanian eruption style a large vigorous eruption with associated open channel or sheet flows producing an extensive flow field by orbit c10 in september 1997 the high mass eruption rate high liquidus temperature at least 1870 k eruption at pillan is the best candidate so far for an active ultramafic magnesium rich komatiitic flow on io a style of eruption never before witnessed the thermal output per unit area from pillan is however consistent with the emplacement of large open channel flows magma temperature at pele is 1600 k if the magma temperature is 1600 k it suggests a komatiitic basalt composition the power output from pele is indicative of a magma volumetric eruption rate of 250 to 340 m3 s 1 although the pele lava lake is considerably larger than its terrestrial counterparts the power and mass fluxes per unit area are similar to active terrestrial lava lakes