monitoring active volcanism with the autonomous sciencecraft experiment on eo 1 abstract the ability to monitor and rapidly react to remote detection of volcanic activity has been greatly improved through use of the autonomous sciencecraft experiment ase an advanced software application installed on a spacecraft in earth orbit ase is a nasa new millennium program experiment demonstrating science driven autonomous command and control of a spacecraft flying on the earth observing 1 eo 1 spacecraft ase successfully detected thermal emission from the mt erebus lava lake on 7 may 2004 having analyzed a hyperion hyperspectral data product on board the spacecraft eo 1 was re tasked by ase to obtain a follow up observation 7 h later and sent a notification of detection of volcanic activity to the ground the entire process was carried out autonomously initial acquisition to receipt on the ground of the positive detection took less than 3 h a process that without ase would have taken weeks the ase thermal classifier has detected several styles of effusive volcanic activity active lava lakes pahoehoe flow fields open channel flows and lava domes ase successfully demonstrated that science driven spacecraft operation greatly enhances science return per returned byte through the identification of the most valuable data allowing prioritization of downlink products and the discarding of null data sets this technology has applications on missions elsewhere in the solar system modified thermal classifiers can be used for detecting and monitoring active volcanism on the jovian satellite io the neptunian moon triton and searching for active volcanism on mars and icy satellites the success of ase is an incentive for future instrument and mission designers to consider on board data processing requirements especially data storage capacity number of processors and processor speed and ram in order to take advantage of this flight proven technology

two classes of volcanic plumes on io abstract comparison of voyager 1 and voyager 2 images of the south polar region of io has revealed that a major volcanic eruption occured there during the period between the two spacecraft encounters an annular deposit 1400 km in diameter formed around the aten patera caldera 311 w 48 s the floor of which changed from orange to red black the characteristics of this eruption are remarkably similar to those described earlier for an eruption centered on surt caldera 338 w 45 n that occured during the same period also at high latitude but in the north both volcanic centers were evidently inactive during the voyager 1 and 2 encounters but were active sometime between the two the geometric and colorimetric characteristics as well as scale of the two annular deposits are virtually identical both resemble the surface features formed by the eruption of pele 255 w 18 s these three very large plume eruptions suggest a class of eruption distinct from that of six smaller plumes observed to be continously active by both voyagers 1 and 2 the smaller plumes of which prometheus is the type example are longer lived deposit bright whitish material erupt at velocities of 0 5 km sec 1 and are concentrated at low latitudes in an equatorial belt around the satellite the very large pele type plumes on the other hand are relatively short lived deposit darker red materials erupt at 1 0 km sec 1 and rather than restricted to a latitudinal band are restricted in longitude from 240 to 360 w both direct thermal infrared temperature measurements and the implied color temperatures for quenched liquid sulfur suggest that hot spot temperatures of 650 k are associated with the large plumes and temperatures 2 in their annuli whereas the large plumes apparently do not two other plumes that occur at either end of the linear feature loki may be intermediate or hybrid between the two classes exhibiting attributes of both additionally loki occurs in the area of overlap in the regional distributions of the two plume classes two distinct volcanic systems involving different volatiles may be responsible for the two classes we propose that the discrete temperatures associated with the two classes are a direct reflection of sulfur s peculiar variation in viscosity with temperature over two temperature ranges 400 to 430 k and 650 k sulfur is a low viscosity fluid orange and black respectively at other temperatures it is either solid or has a high viscosity as a result there will be two zones in io s crust in which liquid sulfur will flow freely a shallow zone of orange sulfur and a deeper zone of black sulfur a low temperature system driven by so 2 heated to 400 to 400 k by the orange sulfur zone seems the best model for the small plumes a system driven by sulfur heated to 650 k by hot or even molten silicates in the black sulfur zone seems the best explanation for the large plume class the large pele type plumes are apparently concentrated in a region of the satellite in which a thinner sulfur rich crust overlies the tidally heated silicate lithosphere so the black sulfur zone may be fairly shallow in this region the prometheus type plumes are possibly confined to the equatorial belt by some process that concentrates so 2 fluid in the equatorial crust

mars south polar hood as observed by the mars climate sounder 1 we have used observations from the mars climate sounder to investigate south polar hood water ice clouds at 12 m including the first systematic examination of the vertical 5 km resolution and nighttime structure we find that the structure and evolution of the polar hood is controlled more strongly by atmospheric temperature variations than by intrinsic fluctuations in water vapor abundance the clouds form as a belt during ls 10 70 phase 1 and ls 100 200 phase 2 during phase 1 the cloud belt extends over a wide latitude range between 30 s and 75 s with a visible column optical depth between 0 075 and 0 15 the cloud belt then evaporates as temperatures warm during phase 2 the cloud belt reappears due to an increase in water vapor as a partial band of low opacity clouds south of the tharsis region and eventually becomes continuous in longitude with a visible column opacity between 0 125 and 0 25 as the southern spring equinox approaches the cloud belt shifts southward following the seasonal cap edge from ls 140 to ls 200 the daytime belt lies about 15 farther south than the nighttime belt due to tidally driven diurnal temperature differences the vertical structure of the cloud belt is consistent within and between the two seasonal phases and is characterized by a thick lower cloud deck and an upper layer whose altitude shifts between the nighttime and daytime because of thermal tidal control of the condensation altitudes overall the southern polar hood is observed to rapidly form and dissipate as the temperature crosses the saturation point of water vapor

imaging of volcanic activity on jupiter s moon io by galileo during the galileo europa mission and the galileo millennium mission the solid state imaging ssi instrument provided the first high and medium resolution views of io as the galileo spacecraft closed in on the volcanic body in late 1999 and early 2000 while each volcanic center has many unique features the majority can be placed into one of two broad categories the promethean eruptions typified by the volcanic center prometheus are characterized by long lived steady eruptions producing a compound flow field emplaced in an insulating manner over a period of years of decades in contrast pillanian eruptions are characterized by large pyroclastic deposits and short lived but high effusion rate eruptions from fissures feeding open channel or open sheet flows both types of eruptions commonly have 100 km tall bright so2 rich plumes forming near the flow fronts and smaller deposits of red material that mark the vent for the silicate lavas

volcanic activity at tvashtar catena io abstract galileo s solid state imager ssi observed tvashtar catena four times between november 1999 and october 2001 providing a unique look at a distinctive high latitude volcanic complex on io the first observation orbit i25 november 1999 resolved for the first time an active extraterrestrial fissure eruption the brightness temperature was at least 1300 k the second observation orbit i27 february 2000 showed a large 500 km 2 region with many small hot regions of active lava the third observation was taken in conjunction with cassini imaging in december 2000 and showed a pele like annular plume deposit the cassini images revealed an 400 km high pele type plume above tvashtar catena the final galileo ssi observation of tvashtar orbit i32 october 2001 revealed that obvious to ssi activity had ceased although data from galileo s near infrared mapping spectrometer nims indicated that there was still significant thermal emission from the tvashtar region in this paper we primarily analyze the style of eruption during orbit i27 february 2000 comparison with a lava flow cooling model indicates that the behavior of the tvashtar eruption during i27 does not match that of simple advancing lava flows instead it may be an active lava lake or a complex set of lava flows with episodic overlapping eruptions the highest reliable color temperature is 1300 k although higher temperatures cannot be ruled out they do not need to be invoked to fit the observed data the total power output from the active lavas in february 2000 was at least 10 11 w

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

crosswell seismic imaging of reservoir changes caused by co 2 injection monitoring of enhanced oil recovery processes with crosswell data has been one of the earliest applications of time lapse geophysics because data with frequencies up to a few kilohertz can often be collected with the crosswell geometry the method can potentially offer imaging resolution of the order of a few feet such resolution is often necessary for time lapse investigation to be useful in building reservoir models and for accurately describing fluid flow in heterogeneous reservoirs

io evidence for silicate volcanism in 1986 infrared observations of io during the 1986 apparition of jupiter indicate that a large eruptive event occurred on the leading side of io on 7 august 1986 universal time measurements made at 4 8 8 7 and 20 micrometers suggest that the source of the event was about 15 kilometers in radius with a model temperature of 900 kelvin together with previously reported events these measurements indicate that high temperature volcanic activity on the leading side of io may be more frequent than previously thought the inferred temperature is significantly above the boiling point of sulfur in a vacuum 715 kelvin and thus constitutes strong evidence for active silicate volcanism on the surface of io

comment on the surface of lo a new model by bruce hapke abstract hapke 1989 icarus 79 56 74 proposed that the surface of io is dominantly basaltic with thin coatings of polysulfur oxide s 2 o ad so 2 however observations and models of the active volcanism indicate that volatiles such as sulfur and so 2 must be more abundant than envisioned by hapke

silicate cooling model fits to galileo nims data of volcanism on io abstract the near infrared mapping spectrometer nims has obtained spectra of volcanoes on the surface of the jovian satellite io fits to data using a silicate cooling model allow us to constrain lava eruption rates and eruption age the thermal signatures of the hot spots are indicative of active and cooling silicate lava flows for large active hot spots maximum ages of flow surfaces detected by nims typically range from days to months although in one case it is nearly 30 years mass eruption rates for the main hot spots are in the range 7 m3 s 1 to 79 m3 s 1 using an average flow thickness of 1 m these mass eruption rates are orders of magnitude less than those implied for large thermal outbursts on io the eruptions observed during june 1996 are most likely of a different eruption style on a much smaller scale the observation analyzed here may be representative of the current background level of volcanic activity on the anti jove hemisphere of io the global mass eruption rate from these non outburst hot spots is calculated to be 43 km3 year equivalent to a global resurfacing rate of about 1 mm year about 10 of the minimum required global resurfacing volume the total observed energy output from the 14 hot spots analyzed is 3 6 1012 w normalized globally these hot spots contribute approximately 10 of io s radiometric heat flux

multi instrument remote and in situ observations of the erebus volcano antarctica lava lake in 2005 a comparison with the pele lava lake on the jovian moon io abstract the stable persistent active lava lake at erebus volcano ross island antarctica provides an excellent thermal target for analysis of spacecraft observations and for testing new technology in the austral summer of 2005 visible and infrared observations of the erebus lava lake were obtained with sensors on three space vehicles terra aster modis aqua modis and eo 1 hyperion ali contemporaneous ground based observations were obtained with hand held infrared cameras this allowed a quantitative comparison of the thermal data obtained from different instruments and of the analytical techniques used to analyze the data both with and without the constraints imposed by ground truth from the thermal camera data in december 2005 the main erebus lava lake ray lake had an area of 820 m2 surface colour temperatures ranged from 575 k to 1090 k with a broad peak in the distribution from 730 k to 850 k total heat loss was estimated at 23 5 mw the flux density was 29 kw m 2 mass flux was estimated at 64 to 93 kg s 1 the best correlation between thermal emission and emitting area was obtained with aster which has the best combination of spatial resolution and wavelength coverage especially in the thermal infrared the high surface temperature of the lava lake means that hyperion data are for the most part saturated uncertainties introduced by the need to remove incident sunlight cause the thermal emission from the hyperion data to be a factor of about two greater than that measured by hand held thermal camera modis also over estimated thermal output from the lava lake by the same factor of two because it was detecting reflected sunlight from the rest of the pixel area the measurement of the detailed temperature distribution on the surface of an active terrestrial lava lake will allow testing of thermal emission models used to interpret remote sensing data of volcanism on io where no such ground truth exists although the erebus lava lake is four orders of magnitude smaller than the lava lake at pele on io the shape of the integrated thermal emission spectra are similar thermal emission from this style of effusive volcanism appears to be invariant excess thermal emission in most pele spectra compared to erebus at short wavelengths

competition between na2so4 and na sulfide in the upper crust of io the na atmosphere of io requires a na s o phase in the outer surface layers considering the various mechanisms for extraction of na to the surface the possible primary phases are na 2o na 2s x and na 2so 4 however regardless of the primary phases brought to the surface the shallow crustal recycling of material implied by the ongoing volcanism will tend to produce thermochemical equilibrium and cause all na to end up as na 2so 4 or na 2s x this hypothesis is investigated by relatively model independent thermodynamic calculations the major assumption is that material is statistically circulated to sufficiently high temperatures by burial that thermochemical equilibrium can be attained for a wide range of assumed crustal pt conditions na 2o will be converted to na 2so 4 during residence in the shallowest crustal regions dominated by liquid so 2 e g so 2 geysers or fumaroles or for any crustal regimes where so 2 and s are in comparable abundances na sulfides will be converted to na 2so 4 however in high temperature low pressure regimes with a low relative abundance of so 2 relative to s e g due to outgasing of so 2 na 2so 4 is converted to na sulfides such regimes could be relatively common on io e g associated with flows lava lakes or shallow intrusions consequently because of thermochemical equilibration in different crustal environments both na 2so 4 and na sulfides will coexist on the io surface

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

ground based observations of io ground based observations are providing new information about the volcanic phenomena at io s surface thermal emission from lava can be seen routinely at infrared wavelengths one result of recent work is the reinvigoration of a familiar theme silicate volcanism in the following paragraphs we will focus on such advances which have resulted from a better understanding of io s thermal emission this emission tells us about ongoing volcanic processes and heat flow io s total heat flow is especially important because of the tidal interactions among the bodies in the jovian system the value of this heat flow not only constrains models for io s interior but also those for jupiter and for the long term orbital evolution of the whole system

wave tracing ray tracing for the propagation of band limited signals part 1 theory many seismic imaging techniques require computing traveltimes and travel paths methods to compute raypaths are usually based on high frequency approximations in situations such as head waves these raypaths minimize traveltime but are not paths along which most of the energy travels we have developed a new approach to computing raypaths using a modification of ray bending that we call wave tracing it computes raypaths and traveltimes that are more consistent with the paths and times for the band limited signals in real data than the paths and times obtained using high frequency approximations wave tracing shortens the raypath while keeping the raypath within the fresnel zone for a characteristic frequency of the signal

active volcanism on io io one of jupiter9s moons has hundreds of active volcanoes many of which are erupting high temperature silicate lavas in his perspective mcewen reviews how data returned by the galileo spacecraft have helped to resolve some questions regarding io9s volcanism but have raised others especially regarding the moon9s internal structure

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

the nature of the volcanic activity at loki insights from galileo nims and ppr data abstract loki is the largest patera and the most energetic hotspot on jupiter s moon io in turn the most volcanically active body in the solar system but the nature of the activity remains enigmatic we present detailed analysis of galileo near infrared mapping spectrometer nims and photopolarimeter radiometer ppr observations covering the 1 5 100 m wavelength range during the i24 i27 and i32 flybys the general pattern of activity during these flybys is consistent with previously proposed models of a resurfacing wave periodically crossing a silicate lava lake in particular our analysis of the i32 nims observations shows over much of the observed patera surface temperatures and implied ages closely matching those expected for a wave advancing counterclockwise at 0 94 1 38 km day the age pattern is different than other published analyses which do not show as clearly this azimuthal pattern our analysis also shows two additional distinctly different patera surfaces the first is located along the inner and outer margins where components with a 3 00 4 70 m color temperature of 425 k exist the second is located at the southwestern margin where components with a 550 k color temperature exist although the high temperatures could be caused by disruption of a lava lake crust some additional mechanism is required to explain why the southwest margin is different from the inner or outer ones finally analysis of the temperature profiles across the patera reveal a smoothness that is difficult to explain by simple lava cooling models paradoxically at a subpixel level wide temperature distributions exist which may be difficult to explain by just the presence of hot cracks in the lava crust the resurfacing wave and lava cooling models explain well the overall characteristics of the observations however additional physical processes perhaps involving heat transport by volatiles are needed to explain the more subtle features

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

formation of mountains on io variable volcanism and thermal stresses abstract thermal stresses are potentially important drivers of io s tectonics and mountain building it has been hypothesized that sustained local or regional shut down of heat pipe volcanism on io could lead to deep crustal heating and large compressive stresses mckinnon w b schenk p m dombard a j 2001 geology 29 103 106 such large stresses would then be relieved by thrust faulting and uplifting of crustal blocks producing mountains like those observed on io here we analyze the tectonic consequences of the heat pipe model in detail considering both the initial thermal stress state of a basalt or peridotite crust created by heat pipe volcanism and relative roles of subsidence stresses due to burial of preexisting layers and thermal stresses arising from variable volcanism and changes in crustal lithosphere thickness we limit the magnitude of the potential subsidence stresses in our study because the magnitude of subsidence stresses can be quite large if not dominant results indicate that for a fixed crustal thickness the region of failure and faulting moves closer to the surface as eruption rate decreases and time increases when the crust melts at its base as volcanism decreases as might occur under steady state tidal heating resulting in crustal thinning the region of failure is brought even closer to the surface naturally when compressive subsidence stresses are included the vertical extent of crust in brittle failure thickens to include most of the lithosphere in contrast increases in eruption rate cause the extent of the region in compressional failure to decrease and be driven very deep in the crust in the absence of sufficient subsidence stress therefore regions of declining volcanism are more likely to produce mountains whereas regions of extensive or increasing volcanism are less likely to do so this is consistent with the observation of a global anticorrelation between mountains and volcanic centers on io finally we find that the choice of crustal composition rheology dry basalt vs dry peridotite has little effect on our results implying that basalt peridotite and komatiite are all similarly stiff in the io environment

maximum energy traveltimes calculated in the seismic frequency band prestack kirchhoff migration using first arrival traveltimes has been shown to produce poor images in areas of complex structure to avoid this problem i propose a new method for calculating traveltimes that estimates the traveltime of the maximum energy arrival rather than the first arrival this method estimates a traveltime that is valid in the seismic frequency band not the usual high frequency approximation instead of solving the eikonal equation for the traveltime i solve the helmholtz equation to estimate the wavefield for a few frequencies i then perform a parametric fit to the wavefield to estimate a traveltime amplitude and phase the images created by using these parameters in a kirchhoff imaging algorithm are comparable in quality to those created using full wavefield finite difference shot profile migration

sulfur flows of ra patera io abstract voyager 1 imaging data have been used to investigate the color and morphology of several radial flow like features at ra patera a broad volcanic structure at approximately 8 latitude and 325 longitude on the galilean satellite io j1 it was found that downstream progressions of flow color and morphology are consistent with lava of a predominately sulfur composition cooling radiatively and erupting in the range of 470 to 520 k at effusion rates at 1010 to 1011 cm3 sec this implies global resurfacing rates by volcanic flows on io of the order of 1 cm year calculated energy content and effusion rates for flows at ra patera using the physical parameters of sulfur are of the order of the largest known terrestial basaltic eruptions and are consistent with calculations of globally available energy

the zamama thor region of io insights from a synthesis of mapping topography and galileo spacecraft data abstract we have studied data from the galileo spacecraft s three remote sensing instruments solid state imager ssi near infrared mapping spectrometer nims and photopolarimeter radiometer ppr covering the zamama thor region of io s antijovian hemisphere and produced a geomorphological map of this region this is the third of three regional maps we are producing from the galileo spacecraft data our goal is to assess the variety of volcanic and tectonic materials and their interrelationships on io using planetary mapping techniques supplemented with all available galileo remote sensing data based on the galileo data analysis and our mapping we have determined that the most recent geologic activity in the zamama thor region has been dominated by two sites of large scale volcanic surface changes the zamama eruptive center is a site of both explosive and effusive eruptions which emanate from two relatively steep edifices zamama tholi a and b that appear to be built by both silicate and sulfur volcanism a 100 km long flow field formed sometime after the 1979 voyager flybys which appears to be a site of promethean style compound flows flow front so2 plumes and adjacent sulfur flows larger possibly stealthy plumes have on at least one occasion during the galileo mission tapped a source that probably includes s and or cl to produce a red pyroclastic deposit from the same vent from which silicate lavas were erupted the thor eruptive center which may have been active prior to voyager became active again during the galileo mission between may and august 2001 a pillanian style eruption at thor included the tallest plume observed to date on io at least 500 km high and new dark lava flows the plume produced a central dark pyroclastic deposit probably silicate rich and an outlying white diffuse ring that is so2 rich mapping shows that several of the new dark lava flows around the plume vent have reoccupied sites of earlier flows unlike most of the other pillanian eruptions observed during the galileo mission the 2001 thor eruption did not produce a large red ring deposit indicating a relative lack of s and or cl gases interacting with the magma during that eruption between these two eruptive centers are two paterae thomagata and reshef thomagata patera is located on a large shield like mesa and shows no signs of activity in contrast reshef patera is located on a large irregular mesa that is apparently undergoing degradation through erosion perhaps from so2 sapping or chemical decomposition of sulfur rich material from multiple secondary volcanic centers

tvashtar awakening detected in april 2006 with osiris at the w m keck observatory abstract we detected a volcanic outburst in io s northern hemisphere on 17 april 2006 with the osiris imaging spectrometer at keck and confirmed it was still erupting on 2 june 2006 the eruption which we name 060417a was located in tvashtar paterae 100 km southeast of the february 2000 eruption the observed temperature was 1240 4 k over a surface area of 60 5 km 2 providing a total thermal output of 7 7 0 9 10 12 w

observing the icy jovian satellites with the galileo photopolarimeter radiometer instrument the photopolarimeter radiometer ppr instrument aboard the galileo spacecraft will go into orbit around jupiter in december 1995 the 23 month tour offers ppr four ganymede encounters three callisto encounters and three europa encounters with maximum ppr resolution varying from 0 5 km to 8 km and typical resolution of 200 km in addition there will be one ganymede one callisto and two europa nontargeted encounters giving maximum ppr resolution from 58 km to 200 km with a typical resolution of 300 km there is a single io encounter before jupiter orbit insertion that will provide resolutions ranging from 400 km to 2 5 km and numerous subsequent opportunities to observe io with resolution as good as 600 km the ppr will be used to study the polarization of reflected sunlight from each satellite over a wide range of phase angles it will also map daytime and nighttime surface temperatures to look for spatial variations in thermophysical properties study volcanic activity on io and look for possible endogenic thermal activity on europa these observation plans are presented

geologic mapping of the amirani gish bar region of io implications for the global geologic mapping of io abstract we produced the first geologic map of the amirani gish bar region of io the last of four regional maps generated from galileo mission data the amirani gish bar region has five primary types of geologic materials plains mountains patera floors flows and diffuse deposits the flows and patera floors are thought to be compositionally similar but are subdivided based on interpretations regarding their emplacement environments and mechanisms our mapping shows that volcanic activity in the amirani gish bar region is dominated by the amirani eruptive center aec now recognized to be part of an extensive combined amirani maui flow field a mappable flow connects amirani and maui suggesting that maui is fed from amirani such that the post voyager designation maui eruptive center should be revised amirani contains at least four hot spots detected by galileo and is the source of widespread bright sulfur flows and active dark silicate flows being emplaced in the promethean style slowly emplaced compound flow fields the floor of gish bar patera has been partially resurfaced by dark lava flows although other parts of its floor are bright and appeared unchanged during the galileo mission this suggests that the floor did not undergo complete resurfacing as a lava lake as proposed for other ionian paterae there are several other hot spots in the region that are the sources of both active dark flows confined within paterae and so2 and s2 rich diffuse deposits mapped diffuse deposits around fractures on mountains and in the plains appear to serve as the source for gas venting without the release of magma an association previously unrecognized in this region the six mountains mapped in this region exhibit various states of degradation in addition to gaining insight into this region of io all four maps are studied to assess the best methodology to use to produce a new global geologic map of io based on the newly released combined galileo voyager global mosaics to convey the complexity of ionian surface geology we find that a new global geologic map of io should include a map sheet displaying the global abundances and types of surface features as well as a complementary gis database as a means to catalog the record of surface changes observed since the voyager flybys and during the galileo mission

post solidification cooling and the age of io s lava flows abstract the modeling of thermal emission from active lava flows must account for the cooling of the lava after solidification models of lava cooling applied to data collected by the galileo spacecraft have until now not taken this into consideration this is a flaw as lava flows on io are thought to be relatively thin with a range in thickness from 1 to 13 m once a flow is completely solidified a rapid process on a geological time scale the surface cools faster than the surface of a partially molten flow cooling via the base of the lava flow is also important and accelerates the solidification of the flow compared to the rate for the semi infinite approximation which is only valid for very deep lava bodies we introduce a new model which incorporates the solidification and basal cooling features this model gives a superior reproduction of the cooling of the 1997 pillan lava flows on io observed by the galileo spacecraft we also use the new model to determine what observations are necessary to constrain lava emplacement style at loki patera flows exhibit different cooling profiles from that expected from a lava lake we model cooling with a finite element code and make quantitative predictions for the behavior of lava flows and other lava bodies that can be tested against observations both on io and earth for example a 10 m thick ultramafic flow like those emplaced at pillan patera in 1997 solidifies in 450 days at which point the surface temperature has cooled to 280 k and takes another 390 days to cool to 249 k observations over a sufficient period of time reveal divergent cooling trends for different lava bodies examples lava flows and lava lakes have different cooling trends after the flow has solidified flows cool faster thin flows solidify and cool faster than flows of greater thickness the model can therefore be used as a diagnostic tool for constraining possible emplacement mechanisms and compositions of bodies of lava in remote sensing data

high temperature silicate volcanism on jupiter s moon io infrared wavelength observations of io by the galileo spacecraft show that at least 12 different vents are erupting lavas that are probably hotter than the highest temperature basaltic eruptions on earth today in at least one case the eruption near pillan patera two independent instruments on galileo show that the lava temperature must have exceeded 1700 kelvin and may have reached 2000 kelvin the most likely explanation is that these lavas are ultramafic magnesium rich silicates and this idea is supported by the tentative identification of magnesium rich orthopyroxene in lava flows associated with these high temperature hot spots

volcanic hotspots on io stability and longitudinal distribution we report the first results of a program to determine the longitudinal distribution of volcanic activity on jupiter s satellite io infrared measurements at 8 7 10 and 20 micrometers have been taken at a variety of orbital longitudes strong variation in the 8 7 and 10 micrometer flux with longitude demonstrates that infrared emission arising from volcanic hotspots on io is strongly concentrated in a few locations analysis of these data suggests that the active volcanic regions observed by the voyager experimenters are still active particularly the region around the feature known as loki another source of flux although of somewhat smaller magnitude is indicated on the opposite hemisphere if these sources are the only major volcanic centers on io then current global heat flow estimates must be revised downward however heat flow from as yet unobserved longitudes hotspots at high latitudes and conducted heat flow must still be measured

evaluation of sulfur flow emplacement on io from galileo data and numerical modeling galileo images of bright lava flows surrounding emakong patera have been analyzed and numerical modeling has been performed to assess whether these flows could have resulted from the emplacement of sulfur lavas on io images from the solid state imaging ssi camera show that these bright white to yellow emakong flows are up to 370 km long and contain dark sinuous features that are interpreted to be lava conduits 300 500 m wide and 100 km long near infrared mapping spectrometer nims thermal emission data yield a color temperature estimate of 344 k 60 k 131 c within the emakong caldera we suggest that these bright flows likely resulted from either sulfur lavas or silicate lavas that have undergone extensive cooling pyroclastic mantling and or alteration with bright sulfurous materials the emakong bright flows have estimated volumes of 250 350 km3 similar to some of the smaller columbia river basalt flows if the emakong flows did result from effusive sulfur eruptions then they are orders of magnitude greater in volume than any terrestrial sulfur flows our numerical modeling results show that sulfur lavas on io could have been emplaced as turbulent flows which were capable of traveling tens to hundreds of kilometers consistent with the predictions of sagan 1979 and fink et al 1983 our modeled flow distances are also consistent with the measured lengths of the emakong channels and bright flows modeled thermal erosion rates are 1 4 m d 1 for flows erupted at 140 180 c which are consistent with the melting rates of kieffer et al 2000 the emakong channels could be thermal erosional in nature however the morphologic signatures of thermal erosion channels cannot be discerned from available images there are planned galileo flybys of io in 2001 which provide excellent opportunities to obtain high resolution morphologic and color data of emakong patera such observations could along with further modeling provide additional information to better constrain whether sulfur lavas produced the emakong flows