V33C-1469 1340h
Streamlining Spacecraft Observation Response to Volcanic Activity Detection Using An Autonomous Sensor Web of Ground and Space-Based Assets.
Streamlining the process by which data of active volcanism are obtained and processed is a desirable goal of volcano monitoring and hazard assessment programs. The JPL Volcano Sensor Web is an application of networked sensor technology that is being applied to volcano monitoring. The Sensor Web team has utilized the University of Hawaii automated system for processing data of volcanic thermal emission obtained by GOES (in geostationary orbits) and MODIS (on the Terra and Aqua spacecraft). This yields alerts on timescales of 15 minutes for GOES and less than 24 hours for MODIS data. Additionally, the Volcano Sensor Web utilizes the Hawaiian Volcano Observatory tiltmeter network (which covers Kilauea and Mauna Loa) which autonomously generates alerts when pre-set thresholds of inflation/deflation, likely to result in effusive activity, are exceeded. On notification, JPL automatically generates a spacecraft command sequence that is then transmitted to Goddard Space Flight Center for uplink to the Earth Observing 1 (EO-1) spacecraft. This enables rapid acquisition of high-spatial resolution hyperspectral (Hyperion) and multispectral (ALI) observations to be obtained of the target volcano as quickly as possible. Extending the use of autonomy, Autonomous Sciencecraft Experiment [1] software onboard EO-1 can then process the data and rapidly report the results (e.g., number and location of thermally active pixels). Ref. [1] Chien, S. et al. "The Earth Observing One Autonomous Science Agent", Proceedings of the Third International Conference on Autonomous Agents and Multi-Agent Systems, New York, New York, July 2004. Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. The tiltmeter AlarmManager software was written by Chris Callendar.
V33C-1470 1340h
Volcanic Landform Classification of Iwate Volcano from DEM-Derived Thematic Maps
Over the last three decades, digital elevation models (DEMs) have been developed as surface data instead of contour lines to allow numerical analysis or modeling of terrain by computer. DEMs have allowed the development of algorithms to rapidly derive slope, relief, convexity, concavity and aspect of any points of surface, and also have allowed the definition of a number of new morphometric measures i.e. openness (Yokoyama et al., 2002). Openness is an angular measure of the relation between surface relief and horizontal distance. Openness has two viewer perspectives. Positive values, expressing openness above the surface, are high for convex forms, whereas negative values describe this attribute below the surface and are high for concave forms. The emphasis of terrain convexity and concavity in openness maps facilitates the interpretation of landforms on the Earth_fs surface. Prima et al. (2003) proposed automated landform classification using openness and slope with genetic factors. This method had been proved to produce good classification for constructional (alluvial plains, alluvial fans and volcanoes) and erosional (hills and mountains) landforms. The capability of this method to classify landforms from DEMs with genetic factors is important because it allows landform evolution to be numerically analyzed. In this study, we adopted this method to classify volcanic landforms of Iwate Volcano from Honshu, Japan, where volcanic landforms were categorized referring to geological map of Iwate Volcano (Doi, 2000). This process took three steps. First, the characteristic of each category was evaluated against the mean and standard deviation of slope, and both positive and negative openness, in two dimensional feature spaces. Second, the characteristic of each category were observed and the combinations of mean and standard deviation of slope and openness showing high separabilities were selected. We found that the standard deviation of slope, positive and negative openness yielded high separabilities of each category and indicated consistency between the trend of categories_f distribution and their geological successions. Third, Mahalanobis distance was used as classification rule to automatically classify the volcanic landforms of Iwate Volcano with those categories. The result shows fine interpretation of volcanic landforms of Iwate Volcano according to their geological successions. The northeastern sector of Iwate Volcano that has relatively young strata was clearly identified against other sectors of the volcano. Although some misclassification occurred in places where the ages of landform formation are relatively close, we considered that the present result is provisionally acceptable because the classified landforms in major accurately replicated many components of volcanic landforms of Iwate Volcano.
V33C-1471 1340h
Interior Layered Deposits in Valles Marineris, Mars: Insights From 3d-Data Obtained by the High Resolution Stereo Camera (HRSC) on Mars Express
The Interior Layered Deposits (ILD) in the Valles Marineris depressions on Mars may be of volcanic or sedimentary origin. Either way, their presence has profound implications for the formation of the Valles Marineris itself. The High Resolution Stereo Camera (HRSC) on board the Mars Express mission obtains high-resolution stereo and multipectral images, which are particularly well suited for the geomorphologic analysis of the ILD. One possible key to decide whether the layers are volcanic or sedimentary is their layering geometry, i.e., their strike and dip. Sedimentary, water-lain deposits should have a horizontal layering following an equipotential line, if no post--depositional processes have tilted the layered sequence. On the other hand, volcanic layers from pyroclastic eruptions, including subglacial eruptions, might be inclined, e.g., in tuff cones or in subglacial volcanoes. The strike and dip of layers should then display a concentric pattern around the vent. Digital Elevation Models and orthoimages derived from HRSC data have been used to measure the strike and dip of several ILD in the troughs of Hebes, Ophir, Candor, Melas, and Juventae Chasmata. In most cases, the layers have dips of 10$^\circ$--20$^\circ$, dipping outward from the centers of the ILD. This pattern is in agreement with a volcanic origin. At Juventae Chasma, the layering of one ILD at --4.5$^\circ$S, 297.3$^\circ$E is subhorizontal. This particular ILD is also distinguished from the other ILD covered by this study by its morphology, as revealed by HRSC, Themis, and MOC images, and by its mineralogy, as revealed by the imaging spectrometer Omega on Mars Express [Bibring et al., COSPAR 2004]. Here, a sedimentary origin seems consistent with our measurements.
V33C-1472 1340h
Olympus Mons Mars: Inferred Changes in Late Stage Effusive Activity Based on {\it Mars Express} High Resolution Stereo Camera Data
Maps of the south flank of Olympus Mons (OM) show the percentage of surface lava flows that were emplaced through lava tubes or channels. Lava tubes are thermally insulated, roofed conduits that transport lava to flow fronts, reflecting long-lived eruptions at low to moderate, fairly steady effusion rates of low viscosity lavas. Lava channels generally result from shorter-lived eruptions and higher, fluctuating effusion rates of higher viscosity lavas. Thus, because channels and tubes tend to result from different eruptive conditions their abundance can be used to characterize the effusive stages of eruptions. We mapped four zones (each 60 by 30 km) extending from the summit of OM (zone 1) to the basal scarp (zone 4). No tube-fed flows (TFF) are present in zone 1. Zone 2 contains up to 40% TFF, while zones 3 and 4 contain 15 to 20% TFF. Fan shaped deposits appear to represent local eruptive centers from which small lava channels radiate. However, these deposits are often associated with TFF upflow; it appears that TFF are disrupted at breaks in slope, forming lava fans, and that this disruption is a controlling factor in the decrease in TFF abundance with distance from the summit. Thus, the fans seem to be the only point sources on the southern flank of OM and their relationship to TFF suggests that in the latest stages of effusive activity the summit was the only eruptive center. Although TFF abundances are not uniform down the flank, at most contacts channels embay TFF. This relationship suggests that the south flank of OM underwent a late-stage change from longer-lived, steady, less viscous, tube-forming eruptions to shorter-lived, fluctuating, more viscous, channel-forming eruptions. Hawaiian shields undergo a similar change in morphology through time; this change could involve (in part) plate tectonics disrupting and increasing the length of the conduit, and/or fractionation of the magma source. In both cases transport of magma to the surface might be more difficult, leading to a change from tube- to channel-forming eruptions. Because Mars probably lacks plate tectonics, we suggest that the change in effusive style on OM is consistent with a cooling planet in which fractionating magmas become more viscous and eruptions become shorter and unsteady. Future research will compare OM with other Tharsis shields to determine if this was a province-wide phenomenon.
V33C-1473 1340h
Topographic Attributes of Three Hawaiian Lava Flows: Implications for Evaluation of Lava Flow Emplacement on Mars
Differential Global Positioning System surveys were carried out recently across portions of three lava flows on the Big Island of Hawaii. Transects crossed an entire flow in several cases, and in other cases provided detailed information about selected flow margins. The 1907 basalt (a'a) flow from the southwestern rift zone of Mauna Loa has easy access at several points via the Ocean View Estates road system; flow thickness ranges from about 1 m near the middle of the eastern flow lobe to more than 10 m toward the distal end of this flow. Several components of a benmoreite (alkali-rich basaltic andesite) flow complex from Mauna Kea were examined near the small community of Mana (with permission of the Parker Ranch management), on the western flank of the volcano. The flows are more than 14,000 years old and completely covered with soil more than a meter thick, but flow morphology at the decameter scale remains very evident in aerial photographs; some benmoreite flows have up to 30 m of relief along their middle reaches. A trachyte flow more than 100,000 years old extends down slope from Puu Waawaa, on the northern flank of Hualalai; Puu Anahulu represents a very advanced stage of magmatic differentiation that resulted in a flow complex with more than 120 m of relief at its southern margin. Width/thickness represents a good discriminator between these three Hawaiian lava flows. Unfortunately, width is often the most difficult parameter to measure remotely for flows on other planets. Recent imaging data from the Thermal Emission Imaging System on the Mars Odyssey spacecraft reveal important new details of lava flows in the Tharsis region of Mars, some of which can be combined with elevation information from the Mars Orbiter Laser Altimeter. The precise topographic characteristics of diverse Hawaiian lava flows provide a new tool for evaluating the potential emplacement conditions for some Martian lava flows, which appear to be more consistent with the basalt to basaltic andesite lava flows than with the highly evolved trachyte flows. Future work, supported by a grant from the NASA Planetary Geology and Geophysics Program, will obtain additional precise topographic information for several Hawaiian flows to expand the topographic data set for comparison with the Martian flows, as well as lava flows on other planetary bodies.
V33C-1474 1340h
Erosion by Flowing Martian Lavas: Insights from Modeling Constrained by MER and Mars Express Data
Low-viscosity lava flows, particularly mafic and ultramafic lavas, have a great potential to degrade underlying substrates by thermo-mechanical erosion during tube- or channel-fed flow emplacement. We used data returned by the recent Mars Exploration Rovers (MER) and {\it Mars Express} missions to provide new constraints to evaluate the potential of Martian lavas to form lava tubes and channels by erosion of flowing lava. Recently published geochemical information on basaltic rocks at Gusev Crater from the Mars rover {\it Spirit} indicates that the dust- and coating-free interiors of the rocks Adirondack, Humphrey, and Mazatzal are primitive, high-Mg basalts (MgO = 11.6-12.8 wt%: {\it McSween et al.}, 2004). Liquidus temperatures of silicate liquids of these compositions would have been $\sim$1250-1270$\deg$C, and liquid dynamic viscosities would have been $\sim$2.5-3.8 Pa s (similar to cold motor oil), suggesting that Martian lavas had the potential for turbulent flow emplacement. From the HRSC experiment on the {\it Mars Express} orbiter comes high-resolution stereo data of Martian lava flows and channels, which provide information on slopes, channel depths, and flow thicknesses at better resolutions than previously available from MOLA data. We have adapted the lava erosion model of {\it Williams et al.} (1998) to Martian conditions and used the MER-based compositions to assess the erosional potential of Martian lava flows. Our first test case is a long lava channel on Hecates Tholus in Elysium Planitia, in which HRSC data show is $>$ 66 km long (from caldera top to base of volcano) and emplaced on slopes between 1.4-8.3$\deg$. Our computer modeling results suggest turbulent emplacement (assuming initially 7.5 m thick flows) with maximum erosion rates of 85-170 cm/day, depending upon the ice content of the basaltic substrate. Further study and application will provide a better understanding of lava emplacement processes on Mars.
V33C-1475 1340h
Lava Flow Mapping at Westdahl Volcano, Alaska, Using SAR and Optical Satellite Imagery
Field mapping of young lava flows at Aleutian volcanoes is logistically difficult. Optical imaging systems, whether air- or space-borne, can be valuable to such mapping efforts, but are often inhibited by persistent cloud cover in this area. These factors have resulted in erroneous estimates of the area and volume calculations of three young lava flows at Westdahl volcano, including its most recent flow (1991-1992). We combined synthetic aperture radar (SAR) data with multispectral Landsat-7 ETM+ imagery to distinguish among the 1991-1992 flow, the 1964 flow, and a pre-1964 flow, and to calculate the flow areas (8.4 km2, 9.2 km2, and 7.3 km2, respectively). By differencing a USGS digital elevation model (DEM) produced in the 1970-80s with a DEM derived from the Shuttle Radar Topography Mission (February 2000), we estimated the average thickness of the 1991-92 flow to be 13 m (± 5 m), which reasonably agrees with field observations of 5 m ~ 10 m. Lava-flow maps produced in this way can be used to augment field mapping and flow-hazards assessment, and to study magma-supply dynamics, and thus, to anticipate future eruptive activity. Based on the recurrence interval of recent eruptions and the results of this study, the next eruption at Westdahl may occur before the end of this decade.
V33C-1476 1340h
Galileo SSI Observations of High Temperature Lavas on Io: Improved Error Analysis and Implications for the Interior
The SSI camera onboard the Galileo spacecraft captured images of incandescent lava on Jupiter's moon Io between 1997 and 2001 at 17 m/pixel to 20 km/pixel. Previous estimates of lava temperature have come from combining the SSI 0.4-1.0 micron data with NIMS mid-infrared data and numerical cooling models. These model results indicated an eruption temperature of $\sim$1600 $\deg$C, implying ultramafic compositions. Improved error analysis of the SSI data improves our brightness, color, and eruption temperature estimates. At Tvashtar Catena we obtained a brightness temperature of 1100 $\deg$C for an active curtain of lava in November of 1999. From the height of the fountains, we estimate the ballistic flight time for the pyroclasts to be $\sim$1 minute. This implies an eruption temperature $\sim$1700 $\deg$C, if the fountain is optically thick. We also find that the hottest pixels from the February 2000 lava flow in Tvashtar Catena had a color temperature of about 1400 $\deg$C. If these pixels contained lava with a wide range of ages, it would imply an eruption temperature approaching 2500 $\deg$C. Alternatively, we suggest that the entire 10$^{5}$ m$^{2}$ area of these pixels contains no lava more than a few seconds old. This allows an eruption temperature of 1600-1700 $\deg$C. These very high lava temperatures are difficult to reconcile with models for the interior of Io. The high temperatures suggest almost complete melting of the mantle. However, the ultramafic crust would be gravitationally unstable over a largely liquid mantle and it would be difficult to generate the tidal heating to drive the observed volcanism. We investigate superheating via viscous dissipation within ascending magma as a possible explanation. If the mantle is largely solid, the expected magma source region temperature is about 1200 $\deg$C, so we require about 500 $\deg$C of superheating. This could be provided if the driving pressure on the magma is about 3 GPa. For buoyancy to provide this driving pressure, the magma needs to be rising from a depth of $>$10$^{4}$ km. The radius of Io is only 1820 km. We conclude that we do not yet understand how Io can have these very hot lavas.
V33C-1477 1340h
Space-based TIR Detection of Volcanic SO$_{2}$ in the North Pacific using ASTER and MODIS
This study focuses on the detection of volcanic SO$_{2}$ in the North Pacific region (NOPAC) which contains over 150 active volcanoes. Ground based UV detection techniques have long been the standard in monitoring total volcanic SO$_{2}$ flux, with satellite sensors used solely during eruptive episodes. Increases in the spectral and spatial resolution of TIR satellite sensors since the launch of NASA's Terra (1999) and Aqua (2002) platforms has provided researchers with a heightened perspective of emitted SO$_{2}$ at active volcanoes and may allow for SO$_{2}$ monitoring in remote volcanic regions. Using the 8.6 μm absorption feature of SO$_{2}$, estimates at select NOPAC volcanoes during both passive degassing and eruptive episodes are determined. On 10 May 2004 at 0840 UTC ASTER detected approximately 380 kt of SO$_{2}$ at Shishaldin (Alaska, USA), which agrees with preliminary field measurements from July 2004. The detection of the eruption of Bezymianny (Kamchatka, Russia) in January 2004 by consecutive Terra and Aqua provided a time series of MODIS data. Analysis of this data set indicates approximately 40 kt of SO$_{2}$ was detected by 0210 UTC on 14 January 2004. These results indicate the versatility and value of this detection technique in the remote NOPAC region.
V33C-1478 1340h
Preliminary Analysis of Thermal Flux Associated With Dome Growth of Bezymianny Volcano Using Spaceborne Thermal Infrared Data
Bezymianny volcano is considered one of the most active volcanoes on the Kamchatka Peninsula, Russia. Bezymianny erupts on average one to two times per year, usually following the same cyclic process from slow growth of the dome to dome failure and collapse. These dome processes are observed in satellite data as variations in thermal flux that result in thermal anomalies. Using satellite data the relationship between thermal anomalies and the growth of active lava domes can be determined using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Advanced Very High Resolution Radiometer (AVHRR), Landsat Enhanced Thematic Mapper (ETM) +, and Moderate Resolution Imaging Spectroradiometer (MODIS). Preliminary thermal flux calculations derived for the fall 2000 eruption of Bezymianny suggest that the thermal flux at Bezymianny increases with time up to the October 2000 collapse of the dome. It is found that increased periods of thermal flux correlate with seismic crisis at the lava dome. Linking these data sets can provide a useful tool to predict future explosive eruptions at Bezymianny. Field measurements of thermal flux were gathered for Bezymianny using a Forward Looking Infrared Radiometer(FLIR) in the summer of 2004. The thermal flux measurements from the field will be compared to the most concurrent satellite data to validate and calibrate observations and to improve satellite derived flux calculations. Eventually, increases in thermal flux will be incorporated into volcano monitoring as a precursor signal to explosive eruptions at domes.
V33C-1479 1340h
Detecting small geothermal features at Northern Pacific volcanoes with ASTER thermal infrared data
The Alaska Volcano Observatory (AVO) and the Kamchatkan Volcanic Eruption Response Team (KVERT) monitor the eruptive state of volcanoes throughout the Aleutian, Kamchatkan, and Kurile arcs. This is accomplished in part by analyzing thermal infrared (TIR) data from the Advanced Very High Resolution Radiometer (AVHRR) and Moderate-resolution Imaging Spectroradiometer (MODIS) sensors at least twice per day for major thermal anomalies. The AVHRR and MODIS 1-km spatial resolution data have been very useful for detecting large and/or high-temperature thermal signatures such as Strombolian activity as well as lava and pyroclastic flows. Such anomalies commonly indicate a major eruptive event is in progress. However, in order to observe and quantify small and/or lower temperature thermal features such as fumaroles and lava domes, higher spatial resolution data with better radiometric and spectral resolution are required. We have reviewed 2600 available night and day time TIR scenes acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) over the volcanoes of the northern Pacific. The current archive spans from March, 2000 to present. ASTER is the only instrument that routinely acquires high spatial resolution (30 - 90 m) night time data over volcanic targets. These data sets typically contain 5 TIR (8-12 microns) with 90 meter spatial resolution and 6 shortwave infrared (SWIR) bands (1-3 microns) with 30 meter spatial resolution. After the general survey of the volcanic arcs, we have focused our efforts on several targets. Mt. Hague, in the Emmons Lake complex on the Alaska Peninsula, has had mostly cloud-free ASTER observations for twenty night time TIR and six daytime TIR since August 2000. A small lake in the lower crater of Mt. Hague has had a history of appearing and disappearing over the last few years. The ASTER data combined with several recent field observations allow us to track the changes in lake area and associated temperatures. With more frequent observations, we hope to determine the mechanism of these changes. The 1975-76 craters and lava flows of New Tolbachik Volcano in central Kamchatka appear as persistent thermal features in clear night time ASTER TIR data with ASTER TIR temperatures as high as $22\deg$C. Handheld FLIR TIR images (~0.5m pixels) from August 2004 show temperatures $>$$176\deg$C on the lava flow and $>$$226\deg$C in the crater wall. Mutnovsky and Gorely Volcanoes in southern Kamchatka also have several persistent thermal features in the ASTER data from late 2001 until at least November 2003. These features correlate to a vigorous fumarole field and crater lakes. The Mutnovsky thermal features were also observed in AVHRR data by KEMSD in March, June, and July 2003. The goal of this work is to better detect changes in current volcano activity or precursors to new activity. Our ongoing survey of the ASTER TIR data has created a database of many small (<90 m) or low temperature (20 to $38\deg$C) thermal features at several volcanoes in the northern Pacific region. We will attempt to observe each of the identified features at least annually using ASTER data as it becomes available over each target.
V33C-1480 1340h
The use of Remote Sensing for the Study of the Relationships Between Tectonics and Volcanism
Observations of geometric relationships between tectonics and volcanism is a fruitful approach in geology. On the one hand analysis of the distribution and types of volcanic vents provides information on the geodynamics. On the other hand tectonic analysis explains the location of volcanics vents. Volcanic edifices often result from regional scale deformation, forming open structures constituting preferred pathways for the rise of magmas. Analysis of the shape and the distribution of vents can consequently provide data on the regional deformation. Remote sensing imagery gives synoptic views of the earth surface allowing the analysis of landforms of still active tectonic and volcanic features. Shape and distribution of volcanic vents, together with recent tectonic patterns are best observed by satellite data and Digital Elevation Models than in the field. The use of radar scenes for the study of the structural relationships between tectonic and volcanic features is particularly efficient because these data express sensitive changes in the morphology. In various selected areas, we show that volcanic edifices are located on tension fractures responsible for fissure eruptions, volcanic linear clusters and elongate volcanoes. Different types of volcanic emplacements can be also distinguished such as tail-crack or horse-tail features, and releasing bend basins along strike-slip faults. Caldera complexes seem to be associated to horse-tail type fault terminations. At a regional scale, the distribution of volcanic vents and their relationships with the faults is able to explain the occurrence of volcanism in collisional areas.
V33C-1481 1340h
Variations in the Characteristics of Craters of the Moon Lava Flows from Vent to Termination: Remotely Sensed Spectra and Field Observations
Developing a method to characterize the physical, chemical and temporal aspects of terrestrial volcanics is a necessary step toward studying volcanics on other planetary bodies. Volcanoes and flows close to populated centers have been studied to varying degree, but remote volcanics remain largely unstudied. Remotely sensed data and derived information can be used to select field sites on Earth and on other planets. Scientists studying volcanics in dangerous areas would benefit from as much advance knowledge of the area as possible before beginning fieldwork. By using satellites and other remote sensing methods, information about the eruptive history can be derived and potentially, the hazard these remote volcanic areas may pose to current and future generations can be estimated. Using Landsat TM, ASTER and other remotely sensed data, the extent and characteristics of lava flows can be examined, but verification and refinement of these methods requires collection of data on the ground. Young lava flows at Craters of the Moon National Park were selected to test methods for remote mapping of recent volcanics. These late Pleistocene to Holocene basalt flows have been mapped to 1:100,000 scale (Kuntz et al, 1988) and have only minor vegetative cover. A range of remotely sensed spectral images were combined to optimize recovery of the mapped flows. Major flow units can be distinguished from each other using unsupervised classification of Landsat TM Bands 1-7, but differentiation of flows within these units presents greater difficulty. Principal component analyses revealed that during the daytime, thermal infrared variations outweigh variations in all other bands. Larger-scale features were observed like edge effects attributable to changes in surface roughness or texture that might occur at flow fronts or at boundaries between flows. Using a digitized version of the geologic map, TM and ASTER data for individual flows were isolated and examined for changes with distance from the source vent or fissure. Several flows were selected for further examination in the field, based on accessibility and scientific interest.
V33C-1482 1340h
Olympus Mass Movement Study from Mars Global Surveyor and Comparison with Io's Volcanoes and Mountains from Galileo Mission
The Olympus and Arsia Mons shield characteristics and surrounding deposits are addressed using data from the Mars Global Surveyor mission, and comparative observations of Io's shield volcanoes and mountains mass wasting features using data from the Galileo mission. Martian and Ionian mass wasting deposits suggest a possible tectonic origin. Martian mass wasting features are observed mainly as apron materials defining concentric ridges around the shield volcanoes Olympus and Arsia Mons. Io's shield volcanoes in the Zamama region are much smaller compared to the Martian examples and do not exhibit extensive mass wasting features. On the other hand, Io's mass wasting deposits show morphological characteristics similar to Martian corrugated apron materials. Io's mountains are typically on the order of tens to a hundred km in length and rise to heights of several kilometers, ranging from high sharp peaks to lower, smooth, rounded mountains. Sulfur-rich layers may provide zones of weakness that could facilitate extensive mass movements.
V33C-1483 1340h
Volcanic Activity of Io Monitored with Keck-10m AO in 2003-2004
With the demise of the Galileo mission, the monitoring of Io volcanic activity lies in the hands of ground-based observers. Our group regularly observed Io with the Keck-10m Adaptive Optics (AO) system and its NIRC-2 camera at 1-5 microns wavelength range. The angular resolution achieved is 0.05" in Kc band (2.2 microns), i.e. 120-140 km on Io at opposition. Approximately 5 to 8 active volcanic centers are usually detected on one 3 or 5 microns AO image with a T between 500 and 1000 K. On rare occasions, we detected the thermal output at shorter wavelength (1-2.5 micron) indicating a colour temperature $>$1300 K. For instance, our data revealed the presence on Jan. 26, 2003, of a bright eruption close to Janus Patera (5$\pm$3S, 39$\pm$3W) with intensity in Lp band (3.8 micron) of 11$\pm$1 GW/sr/micron and $\sim$2 GW/sr/micron in Kc band (2.2 micron). Another bright eruption close to Tupan Patera (16$\pm$4S, 137$\pm$4W) was seen on Mar. 8, 2003 (UT) with a I(Lp)=18 $\pm$1 GW/sr/micron and I(Kc)$\sim$3 GW/sr/micron. More recently, data taken on May 28 and 30, 2004, show the thermal emission of an eruptive center (called 0405A) located at 17$\pm$2 S, 6$\pm$1W (close to Ilmarinera Patera which has never been seen active) with a I(Kc)$\sim$7 GW/sr/micron and I(Lp)=166$\pm$6 GW/sr/micron. This energetic eruption was also detected in H band (1.6 micron) with I(H)$\sim$3 GW/sr/micron. Because we obtained the brightness of these eruptions in at least three different wavelengths, we can perform a more precise analysis of their activity using a basaltic cooling lava flow model (Davies, 1996). In the case of 0405A, we can conclude that we are observing an episode of fire-fountaining (a young, hot event) whose total output is estimated to $\sim$9E12 W (i.e. 10% of Io average total output), more energetic than Tvashtar 2001. The source of these active centers and their activity will be compared with previous Galileo NIMS/SSI observations. We will conclude describing how the future use of AO technique will help to monitor and understand this extraterrestrial and exotic volcanism.
http://astron.berkeley.edu/~fmarchis/Science/Io/