low to medium temperature phase equilibria in a gas of solar composition equilibrium mineral assemblages in a gas of solar composition have been calculated in the temperature and pressure ranges of 423 1023 k and 1 to 10 8 bar respectively the results include the modal percent variation of all condensates and the chemical compositions of ideal and non ideal coexisting solid solutions the major mineral assemblage stable over most of the pressure and temperature field is and fe ni alloys olivine orthopyroxene clinopyroxene plagioclase ilmenite other minerals entering the field are orthoclase at 628 k and troilite fes at 621 k both with no effect of variation in pressure rutile is stable in parts of the high temperature field a typical model percent composition above 621 k is fe ni 2 46 fe ni 40 26 olivine 28 94 orthopyroxene 18 25 clinopyroxene 6 26 plagioclase 3 56 and ilmenite 0 27 t 663 k p 10 4 bar below 621 k there is a marked drop in the average density of the material a small amount of almandine rich garnet appears at 533 k the temperature of appearance decreasing slightly with decreasing pressure at low temperatures biotite tremolite and talc are stable at high pressures while graphite becomes important below 10 7 bar compositions of plagioclase olivine orthopyroxene ilmenite and garnet are found to be potential cosmobarometers and cosmothermometers

concentric crater fill in utopia planitia history and interaction between glacial brain terrain and periglacial mantle processes abstract at martian mid to high latitudes the surfaces of potentially ice rich features including concentric crater fill lobate debris aprons and lineated valley fill typically display a complex texture known as brain terrain due to its resemblance to the complex patterns on brain surfaces in order to determine the structure and developmental history of concentric crater fill and overlying latitude dependent mantle ldm material brain terrain and polygonally patterned ldm surfaces are analyzed using hirise images from four craters in utopia planitia containing concentric crater fill brain terrain and mantle surface textures are classified based on morphological characteristics 1 closed cell brain terrain 2 open cell brain terrain 3 high center mantle polygons and 4 low center mantle polygons a combined glacial and thermal contraction cracking model is proposed for the formation and modification of the brain terrain texture of concentric crater fill a similar model related to thermal contraction cracking and differential sublimation of underlying ice is proposed for the formation and development of polygonally patterned mantle material both models require atmospheric deposition of ice likely during periods of high obliquity but do not require wet active layer processes crater dating of brain terrain and mantled surfaces suggests a transition at martian mid latitudes from peak glacial conditions occurring within the past 10 100 my to a quiescent period followed by a cold desert periglacial period during the past 1 2 my

analysis of chondritic interplanetary dust thin sections abstract chondritic interplanetary dust particles idps are heterogeneous aggregates of predominantly submicrometer mineral grains and carbonaceous material whose bulk compositions agree within a factor of two with type ci cm carbonaceous chondrites the mineralogy and petrography of 25 such particles were studied by analytical electron microscopic examination of ultramicrotomed thin sections 500 1000a thick four classes of chondritic idps were recognized referred to as pyroxene olivine smectite and serpentine and their relative abundances were 9 4 10 2 respectively pyroxene and olivine particles are porous assemblages of anhydrous mineral grains glass and carbonaceous material smectite and serpentine particles are low porosity objects whose matrices contain layer silicates and glassy material quantitative thin film analyses indicate that pyroxene particles most closely resemble material emitted from comet halley smectite particles may have formed from pyroxene particles by aqueous alteration of glass and enstatite crystals serpentine particles are the only class that are similar to the matrices of carbonaceous chondrites but these are the least abundant chondritic idps collectively chondritic particles are a mineralogically diverse group of extraterrestrial materials

mineralogy of chondritic interplanetary dust particles from a mineralogical survey of approximately 30 chondritic micrometeorites collected from the lower stratosphere and studied in detail using current electron microscopy techniques it is concluded that these particles represent a unique group of extraterrestrial materials these micrometeorites differ significantly in form and texture from components of carbonaceous chondrites and contain some mineral assemblages which do not occur in any meteorite class electron microscope investigations of chondritic micrometeorites have established that these materials 1 are extraterrestrial in origin 2 existed in space as small objects 3 endured minimal alteration by planetary processes since formation and 4 can suffer minimal pulse heating 600 c on entering earth s atmosphere the probable sources for chondritic interplanetary dust particles idps are cometary and asteroidal debris and perhaps to a lesser extent interstellar regions these sources have not been conclusively linked to any specific mineralogical subset of idp although the chondritic porous cp aggregate is considered of likely cometary origin chondritic idps occur in two predominant mineral assemblages 1 carbonaceous phases and phyllosilicates and 2 carbonaceous phases and nesosilicates or inosilicates although particles with both types of silicate assemblages are observed olivines pyroxenes layer silicates and carbon rich phases are the most commonly occurring minerals in many chondritic idps other phases often observed in variable proportions include sulphides spinels metals metal carbides carbonates and minor amounts of sulphates and phosphates individual mineral grain sizes range from micrometers primarily pyroxenes and olivines to nanometers with the predominant size for all phases less than 100 nm specific mineral characteristics for particular chondritic idps provide an indication of processes which may have occurred prior to collection in the earth s stratosphere for example pyroxene mineralogy in some chondritic aggregates is consistent with condensation from a vapor phase and we consider with condensation in a turbulent solar nebula at relatively low temperatures 1000 c carbonaceous phases present in other cp aggregates have been used to imply low temperature formation processes such as fischer tropsch synthesis 530 c or carbonization and graphitization 315 c alteration processes have been implicated in the formation of some layer silicates in cp aggregates and may have involved hydrocryogenic alteration at 0 c in general interpretations of transformation processes on submicrometer size minerals in chondritic idps are consistent with formation at a radius equivalent to the asteroid belt or greater during the later stages of solar nebula evolution using currently available models

size distributions in two porous chondritic micrometeorites quantitative size measurements of granular units gus and nanometer sized minerals in these units in two porous chondritic micrometeorites are investigated for the information that they carry on the processes in the early solar system the matrix of these micrometeorites consist of loosely packed 0 1 m sized gus these objects were a major component of the solar nebula dust that accreted into protoplanets the matrix in micrometeorite w7010 a2 has a fractal dimension with a small coefficient d 0 83 that supports efficient sticking of carbon rich gus during accretion the fractal nature of the matrix provides a way to calculate the density using the aggregate size the resulting very low density for porous chondritic micrometeorites is 0 08 0 14 g cm 3 which supports the view that they are the solid debris from unconsolidated solar system bodies e g comet nuclei or regolith deposits on carbon rich asteroids chondritic gus contain ultrafine olivines pyroxenes and sulfides embedded in hydrocarbons and amorphous carbons nanocrystals in the micrometeorites w7010 a2 and u2015 b show log normal size distributions the high incidence of disk shaped grains a changeover from disk shaped to euhedral grains the unevolved nature of the size distributions and multiple populations for grains 127 nm in size are consistent with continuous post accretion nucleation and growth in amorphous gus including coarsening via ostwald ripening

variation of mineralogy and organic material during the early stages of aqueous activity recorded in antarctic micrometeorites abstract micrometeorites mms recovered from surface snow near the dome fuji station antarctica are almost free from terrestrial weathering and contain very primitive materials and are suitable for investigation of the evolution and interaction of inorganic and organic materials in the early solar system we carried out a comprehensive study on seven porous and fluffy mms four chondritic porous cp mms and three fluffy fine grained fluffy fg mms and one fine grained type 1 fg c1 mm for comparison with scanning electron microscope transmission electron microscope x ray absorption near edge structure analysis and secondary ion mass spectrometer they show a variety of early aqueous activities four out of the seven cp mms contain glass with embedded metal and sulfide gems and enstatite whiskers platelets and do not have hydrated minerals despite the same mineralogy organic chemistry of the cp mms shows diversity two of them contain considerable amounts of organic materials with high carboxyl functionality and one of them contains nitrile c n and or nitrogen heterocyclic groups with d and 15 n enrichments suggesting formation in the molecular cloud or a very low temperature region of the outer solar system another two cp mms are poorer in organic materials than the above mentioned mms organic material in one of them is richer in aromatic c than the cp mms mentioned above being indistinguishable from those of hydrated carbonaceous chondrites in addition bulk chemical compositions of gems in the latter organic poor cp mms are more homogeneous and have higher fe si mg fe ratios than those of gems in the former organic rich cp mms functional group of the organic materials and amorphous silicate in gems in the organic poor cp mms may have transformed in the earliest stage of aqueous alteration which did not form hydrated minerals three fluffy fg mms contain abundant phyllosilicates showing a clear evidence of aqueous alteration phyllosilicates in thee mms are richer in fe than those in hydrated idps typical fine grained hydrated fg c1 mms and hydrated carbonaceous chondrites one of the fluffy fg mms contains amorphous silicate which is richer in fe than gems and contains little or no nanophase fe metal but contains fe sulfide because the chemical compositions of the amorphous silicate are within the compositional field of gems in cp idps the amorphous silicate may be alteration products of gems the entire compositional field of gems in the cp mms and the amorphous silicate in the fluffy fg mm matches that of the previously reported total compositional range of gems in idps one fluffy fg mm contains mg rich phyllosilicate along with fe rich phyllosilicate and mg fe carbonate mg rich phyllosilicate and mg fe carbonate may have been formed through the reaction of fe rich phyllosilicate mg rich olivine and pyroxene and water with c bearing chemical species these data indicate that cp mms and fluffy fg mms recovered from antarctic surface snow contain materials that throw a light on the earliest stages of aqueous alteration on very primitive solar system bodies because mineralogy and isotopic and structural features of organic materials in d10ib009 are comparable with isotopically primitive idps its parent body could be comets or icy asteroids showing mass ejection active asteroids by contrast organic poor cp mms may have experienced the earliest stage of aqueous alteration and fluffy fg mms experienced weak aqueous alteration the precursor materials of the parent bodies of fluffy fg mms probably contained abundant gems or gems like materials like cp idps which is common to fine grained matrices of very primitive carbonaceous chondrites such as cr3s however highly porous nature of organic poor cp mms and fluffy fg mms suggests that parent bodies of these mms must have been much more porous than the parent bodies of primitive carbonaceous chondrites given no phyllosilicate among the returned samples of 81p wild 2 comet the mms may have been derived from porous icy asteroids such as active asteroids as well as p and d type asteroids rather than comets

detection of a crack like conduit beneath the active crater at aso volcano japan to constrain the source of long period tremors lpts we deployed a very dense broadband seismic network consisting of totally twenty four stations around the active crater of aso volcano in kyushu japan the spatial variation of the observed signal amplitudes reveals that the source of lpts consists of an isotropic expansion contraction and an inflation deflation of an inclined tensile crack with a strike almost parallel to the chain of craters the detected crack has a dimension of 1 km and its center is located a few hundred meters southwest of the active crater at a depth of about 1 8 km the extension of the crack plane meets the crater chain including the active fumarole at the surface suggesting that the crack has played an important role in transporting gasses and or lava to the craters from below this work also demonstrates a powerful usage of broadband seismometers as geodetic instruments to constrain subsurface structures at active volcanoes

ferrian saponite from the santa monica mountains california u s a earth characterization as an analog for clay minerals on mars with application to yellowknife bay in gale crater ferrian saponite from the eastern santa monica mountain near griffith park los angeles california was investigated as a mineralogical analog to smectites discovered on mars by the chemin x ray diffraction instrument onboard the mars science laboratory msl rover the martian clay minerals occur in sediment of basaltic composition and have 02 l diffraction bands peaking at 4 59 a consistent with tri octahedral smectites the griffith saponite occurs in basalts as pseudomorphs after olivine and mesostasis glass and as fillings of vesicles and cracks and has 02 l diffraction bands at that same position we obtained chemical compositions by electron microprobe x ray diffraction patterns with a lab version of the chemin instrument mossbauer spectra and visible and near ir reflectance vnir spectra on several samples from that locality the griffith saponite is magnesian mg mg fe 65 70 lacks tetrahedral fe 3 and octahedral al 3 and has fe 3 fe from 64 to 93 its chemical composition is consistent with a fully tri octahedral smectite but the abundance of fe 3 gives a nominal excess charge of 1 to 2 per formula unit the excess charge is likely compensated by substitution of o 2 for oh causing distortion of octahedral sites as inferred from mossbauer spectra we hypothesize that the griffith saponite was initially deposited with all its iron as fe 2 and was oxidized later x ray diffraction shows a sharp 001 peak at 15 a 00 l peaks and a 02 l diffraction band at the same position 4 59 a and shape as those of the martian samples indicating that the martian saponite is not fully oxidized vnir spectra of the griffith saponite show distinct absorptions at 1 40 1 90 2 30 2 32 and 2 40 m arising from h 2 o and hydroxyl groups in various settings the position of the 2 31 m spectral feature varies systematically with the redox state of the octahedrally coordinated fe this correlation may permit surface oxidation state to be inferred in some cases from vnir spectra of mars obtained from orbit and in any case ferrian saponite is a viable assignment for spectral detections in the range 2 30 2 32 m

tof sims analysis of interplanetary dust three interplanetary dust particles idps collected in the stratosphere were analyzed with imaging time of flight secondary ion mass spectrometry tof sims to investigate the elemental distribution within these particles at high lateral resolution and to demonstrate the abilities of this new technique for the analysis of idps and other microsamples this study should furthermore show that it is possible to correlate tof sims data and tem observations of the same interplanetary dust particle element ratios for 15 different elements relative to si were determined using sims sensitivities from analyses of several standards the tof sims results show inhomogeneous distribution and large deviations from chondritic abundances for several elements in idp u2015g1 whereas w7029 a27 and l2005p9 show chondritic element ratios and a relatively homogeneous distribution respectively these results which are comparable with previous results obtained by different techniques demonstrate the reliability of tof sims even for quantitative measurements in u2015g1 halogen and sulphur enrichments were observed in an extremely fine grained fe oxide phase this can easily be explained by contamination processes in the stratosphere

three dimensional p velocity structure of the crust below newberry volcano oregon utilizing teleseismic p residuals we have detected a column of high p velocity material extending from within 10 km of the surface below the summit of newberry volcano oregon to midcrustal depths near 25 km we interpret this column to be the expression of a swarm of predominantly subsolidus gabbroic sills and dikes which were intruded as the volcano was built the high p velocities observed below the volcano severely limit the size of magma chambers which could presently exist in the crust below newberry volcano those possible include a few percent of partial melt distributed through large volumes of a mafic intrusion zone in the midcrust a few smaller higher melt fraction zones in the midcrust with dimensions less than 6 km and whose aggregate volume is only a few percent of enclosing volumes of 200 km sup 3 small magma bodies with dimensions of a few kilometers located within the upper 10 km of the crust or a mafic crystal rich magma of arbitrary dimensions located in the upper few km the low p velocities detected in the upper 4 km beneath the center of the summit caldera may be partially caused by a magma chamber in the second ofmore these catagories less

mechanism of phreatic eruptions at aso volcano inferred from near field broadband seismic observations broadband seismometers deployed at aso volcano in japan have detected a hydrothermal reservoir 1 to 1 5 kilometers beneath the crater that is continually resonating with periods as long as 15 seconds when phreatic eruptions are observed broadband seismograms elucidate a dynamic interplay between the reservoir and discharging flow along the conduit gradual pressurization and long period 20 seconds pulsations of the reservoir during the 100 to 200 seconds before the initiation of the discharge followed by gradual deflation of the reservoir concurrent with the discharging flow the hydrothermal reservoir where water and heat from the deeper magma chamber probably interact appears to help control the surface activity at aso volcano

pregraphitic and poorly graphitised carbons in porous chondritic micrometeorites abstract two forms of crystalline carbon in porous chondritic micrometeorites w7029e5 u2011c2 and u2022c7 c8 are mixed layered pregraphitic carbons with c c h o n at 0 45 this bulk composition is inferred from the presence of three groupings of d 002 basal spacings at 0 45 nm 0 37 nm and 0 348 nm mixed layered carbons represent incomplete carbonisation and graphitisation of precursor material in u2022c7 c8 carbonisation mostly involved volatile loss the formation of pregraphitic carbons indicates a sustained thermal regime in parent bodies of these micrometeorites i e short period comets outer belt asteroids or protocomet nuclei temperatures of the sustained thermal regime remain unspecified but carbon reactions were probably facilitated by catalytic support from layer silicates in these samples poorly graphitised carbon in u2022c7 c8 formed during a transient thermal event which is most likely flash heating during micrometeoroid deceleration in the earth s atmosphere

layer silicates in a chondritic porous interplanetary dust particle analytical electron microscopy on individual grains from a portion of a chondritic porous interplanetary dust particle aggregate w7029c1 from the nasa johnson space center cosmic dust collection shows that layer silicates compose 50 percent of the silicate fraction examined these layer silicates can be classified into two distinct crystallochemical groups 1 fine grained polycrystalline smectite minerals and 2 well ordered single crystals of kaolinite and mg poor talc the layer silicates in this portion of sample w7029 asterisk a are dissimilar to those described in other chondritic porous aggregates the predominant layer silicate assemblage in w7029 asterisk a indicates that heating of the aggregate during atmospheric entry was brief and probably to a temperature less than 300c comparison with terrestrial phyllosilicate occurrences suggests that some layer silicates in aggregate w7029 asterisk a may have been formed by alteratiton from preexisting silicate minerals at low temperatures less than 25c after aggregate formation

dynamic pyrometamorphism during atmospheric entry of large 10 micron pyrrhotite fragments from cluster idps petrological changes in ni free and low ni pyrrhotite and much less in pentlandite during atmospheric entry flash heating of the sulfide idps l2005e40 l2005c39 and l2006a28 support 1 ferrous sulfide oxidation with vacancy formation and fe 3 ordering and 2 fe oxide formation and sulfur vapor loss through abundant vesicles melting of metastable chondritic aggregate materials at the idp surface has occurred all changes e g formation of a continuous maghmite rim proceeded as solid state reactions at a peak heating temperature of 700 c this temperature in combination with particle size and density suggest a 10 km s 1 entry velocity the idps probably belonged to cluster idps that entered the atmosphere with near earth or earth crossing asteroid velocities they could be debris from extinct or dormant comet nuclei which is consistent with shock comminution of pyrrhotite in these idps

enhanced residence of submicron si rich volcanic particles in the lower stratosphere abstract abundant submicron si rich grains were collected in the lower stratosphere between may 1981 and january 1982 analytical electron microscopy shows that the morphology surface features and chemical compositions of these platey grains are consistent with keatite keatite forms by devitrification of amorphous si rich grains that condensed in ascending volcanic eruption clouds low settling rates for platey grains should cause concentration of si rich grains in the stratosphere during extended periods of volcanic activity such a concentration is not observed probably because the grains were present as small aggregates with greater settling rates aggregation did not occur in the atmosphere because collision frequencies are too low thus aggregation took place in the volcanic cloud the faster settling rates for the aggregates is still sufficiently slow to increase the amount of small volcanic particles in the stratosphere thereby enhancing the amount of sites for heterogeneous aerosol nucleation

a new variant of saponite rich micrometeorites recovered from recent antarctic snowfall abstract eight saponite rich micrometeorites with very similar mineralogy were found from the recent surface snow in antarctica they might have come to earth as a larger meteoroid and broke up into pieces on earth because they were recovered from the same layer and the same location of the snow synchrotron x ray diffraction xrd analysis indicates that saponite mg fe carbonate and pyrrhotite are major phases and serpentine magnetite and pentlandite are minor phases anhydrous silicates are entirely absent from all micrometeorites suggesting that their parental object has undergone heavy aqueous alteration saponite serpentine ratios are higher than in the orgueil ci chondrite and are similar to the tagish lake carbonaceous chondrite transmission electron microscope tem observation indicates that serpentine occupies core regions of fine grained saponite pyrrhotite has a low ni concentration and mg fe carbonate shows unique concentric ring structures and has a mean molar mg mg fe ratio of 0 7 comparison of the mineralogy to hydrated chondrites and interplanetary dust particles idps suggests that the micrometeorites are most similar to the carbonate poor lithology of the tagish lake carbonaceous chondrite and some hydrous idps but they show a carbonate mineralogy dissimilar to any primitive chondritic materials therefore they are a new variant of saponite rich micrometeorite extracted from a primitive hydrous asteroid and recently accreted to antarctica

three dimensional seismic velocity structure beneath aso volcano kyushu japan tomographic results for p and s wave velocity structure beneath the active aso volcano kyushu japan using 800 well recorded earthquakes and ten shots recorded by an eight station seismic network are presented a 68 variance reduction was achieved upon simultaneous inversion for hypocenter and velocity structure well resolved velocity anomalies associated with the active crater reveal heterogeneity up to 26 slower and 18 faster in p velocity and up to 31 slower and 22 faster in s velocity than the one dimensional model the largest anomaly is seen over the upper 11 km in the central and northern parts beneath the central cones two low velocity regions are imaged the first region a 10 15 km region encompassing the upper 3 km centered near the caldera wall at tateno valley is characterized by p velocities up to 19 slower 20 for s the second low velocity region is associated with the central cones and active magma conduit system at 6 km depth velocities as low as 4 3 km s up to 26 in p and 2 km s 31 slower in s characterize the 7 km wide volume the magma chamber is roughly spherical in shape centered at 6 km depth flattens at 10 km depth and is located between mt kishima mt eboshi and mt naka the present focus of magmatism a sharp velocity contrast at the depth of 3 km with high velocities to the southwest and lower velocities to the northeast characterizes different abutting structures associated with the oita kumamoto tectonic line

bulk mineralogy of individual micrometeorites determined by x ray diffraction analysis and transmission electron microscopy abstract bulk mineralogy of individual fine grained micrometeorites from 50 to 200 m in diameter was determined on the basis of the powder x ray diffraction patterns and the observation of internal textures by a transmission electron microscope tem x ray diffraction analysis of 56 micrometeorites indicated that 42 11 and 3 samples are olivine rich pyroxene rich and phyllosilicate rich micrometeorites respectively among the phyllosilicate rich micrometeorites one contains saponite and other two contain serpentine no samples contain both saponite and serpentine we found that saponite rich micrometeorite was weakly heated which results in shrinkage of 001 basal spacing of saponite down to 9 7 a and that cronstedtite which is commonly contained in cm chondrites occurs in serpentine rich micrometeorites micrometeorites that consist entirely of anhydrous minerals and amorphous phases are predominant in the samples studied the major phases of such micrometeorites are olivine low ca pyroxene magnetite and fe sulfide and the average abundances are 65 17 11 and 7 wt respectively when the total abundance of the four minerals are normalized to 100 wt the relative mineral abundance varies greatly between samples low ca pyroxene olivine ratios range from 0 to 3 5 with a mean of 0 3 tem observations of inner portions of some micrometeorites revealed that they are aggregates of very small equigranular grains 100 nm of olivine magnetite or low ca pyroxene olivine magnesiowustite the textures are very similar to those of hydrous carbonaceous chondrite that was experimentally heated to temperature below melting point thus suggesting that the micrometeorites had been hydrous particles but were decomposed by the brief heating upon atmospheric entry it is newly found that magnesiowustite was formed in micrometeorites instead of magnetite as a product of phyllosilicate decomposition under low oxygen fugacity the decomposed hydrous micrometeorites gave two types of characteristic x ray diffraction patterns 1 broad olivine and magnetite reflections or 2 variable intensities of magnesiowustite reflections together with magnetite low ca pyroxene and olivine reflections twenty nine olivine or pyroxene rich micrometeorites showed such diffraction patterns thus suggesting that more than half of micrometeorites investigated must be decomposed hydrous particles the results confirmed that hydrous dust particles are much more abundant in the interplanetary space than in the micrometeorites recovered on the earth

aqueous alteration in five chondritic porous interplanetary dust particles abstract analytical electron microscope analysis of stratospheric micrometeorites show that layer silicates are common albeit minor constituents in five particles of the nominally anhydrous subclass of chondritic porous cp interplanetary dust particles idps these layer silicates are single crystal na k rich smectite minerals illite kaolinite and less common pyrophyllite mica and rare talc rare non stoichiometric crystalline feldspars of probable authigenic origin occur in cp idp w7029e5 the feldspars are low anorthite and undetermined na k alkali feldspar polymorphs similar al2o3 al2o3 sio2 ratios and alkali content of feldspars and layer silicates suggest a genetic relationship between these minerals whereby layer silicates form during aqueous alteration in the case of cp idp w7029e5 alteration occurred in a mildy acidic ph 5 7 fluid at 175 195 c if cp idps are solid debris from short period comets the observations give evidence for mineralogical and chemical activity in nuclei of short period comets if an asteroidal origin for these cp idps can be established these observations provide a window to the processes that may ultimately lead to fully hydrated carbonaceous chondrite matrices

thermal and crustal structure of the aso volcano and surrounding regions constrained by gravity and magnetic data japan abstract the aso volcano forms a large caldera that is one of the most active volcanoes in japan much evidence suggests the existence of a high temperature zone beneath the active central cones of the aso volcano and a recent study using seismic observations revealed an attenuation in amplitude of seismic waves that pass through the central region of the aso caldera the sww nee trending futagawa active fault a part of the oita kumamoto tectonic line which dips north lies to the west of the caldera and joins the caldera rim but there are no scars within the caldera an elongate magnetic positive anomaly from the central cones to the west exists close to the futagawa fault this anomaly connects the central cones and the two lateral volcanoes west to the caldera magnetic analyses through spectral method and forward modeling delineate a highly magnetized two dimensional buried prism source dipping north beneath the fault the lower bounds are about 10 km depth outside the caldera and quite shallow depths of about 3 km inside the caldera the area to the north of the oita kumamoto tectonic line forms a gravity depression whereas the area to the south is a regional gravity high a two layered two dimensional gravity model yields a normal fault dipping north with a throw of 1 3 km whereas a multi layered two dimensional gravity model gives a depression of high density basement within the caldera the greatest depth is about 2 km below the surface available temperature depth data suggest the possibility of a sudden change between the inside high temperature zone and the outside low temperature zone of the caldera therefore the difference in the lower boundary of magnetic sources between the area inside and outside the caldera is possibly attributed to the difference of depth of the curie point magnetic sources along the futagawa fault are likely to be related to materials produced by the volcanic activity if so the passage for magma for aso volcanism could be along the futagawa fault

determination of shear and compressional wave velocity variations and hypocenter locations in a rapidly inflating caldera the campi flegrei during 1982 1985 the campi flegrei caldera underwent a large h 1 7 m rapid hmax 2 mm day 1 and localized radius 6 km uplift p and s arrival times from three component digital seismograms recorded during this period have been used to invert for hypocenter locations and for three dimensional shear and compressional velocity to 3 km first order residual based tomography shows a significant and well resolved high p s ratio anomaly for the volume encompassing the central caldera and the active solfatara crater three dimensional tomographic inversion resolves this central anomaly as a zone of depressed p and s with a high 2 1 p s ratio the three dimensional velocity model and hypocenter distribution are consistent with modeling the central caldera as a zone of nearly water saturated cracks presumably a result of recurrent inflation and deflation in a zone with a shallow water table although the presence of small shallow magma bodies is not precluded

an investigation of the presence and nature of phyllosilicates on the surfaces of c asteroids by an analysis of the continuum slopes in their near infrared spectra abstract to understand the nature of c asteroid surfaces which are often related to phyllosilicates and c chondrites we report near infrared spectra for a suite of phyllosilicates heated to 100 1100 c in 100 c intervals and compare the results for telescope irtf spectra for 11 c asteroids as c asteroids have relatively featureless spectra we focus on continuum plots 1 0 1 75 m slope against 1 8 2 5 m slope we compare the continuum plots of the 11 c asteroids and our heated phyllosilicates with literature data for c chondrites the ci cr ck and cv chondrite meteorites plot in the c asteroid field whereas cm chondrites plot in a close but discrete field all are well separated from the large phyllosilicate field heating kaolinite and montmorillonite to 700 c moves their continua slopes into the c asteroid field whereas chlorite and serpentine slopes move into the cm chondrite field water losses during heating are generally 10 15 wt and were associated with a 20 70 albedo drop our data are consistent with surfaces of the c asteroids consisting of the dehydration products of montmorillonite whereas the cm chondrites are the dehydration products of serpentine and chlorite the presence of opaque minerals and evaporites does not provide quantitative explanations for the difference in continua slopes of the phyllosilicates and c asteroids the cm chondrites can also be linked to the c asteroids by heating we suggest that the cm chondrites are interior samples and the presence of a 3 m feature in c asteroid spectra also indicates the excavation of material

vp vs ratios in the yellowstone national park region wyoming abstract in this paper we study the variation of v p v s and poisson s ratio in the yellowstone national park region using earthquakes which were well recorded by a local seismic network we find that the average v p v s value within the geothermally active yellowstone caldera is about 7 lower than in the area outside the caldera within the caldera itself there may be a further 2 7 reduction of v p v s in the hydrothermally active norris geyser basin the upper and lower geyser basins and the yellowstone lake and mud volcano regions after considering various possible causes for v p v s changes such as geologic and structural differences thermal effects partial melting and hydrothermal activity we conclude that the most plausible explanation for the observed v p v s reduction is the presence of hot water at temperatures and pore pressures near the water steam transition in the caldera geothermal reservoirs