the temperature and width of an active fissure on enceladus measured with cassini vims during the 14 april 2012 south pole flyover abstract the width and temperature of the active fissures on saturn s satellite enceladus provide key observable constraints on physical models of these geyser like eruptions we analyze a sequence of high spatial resolution near infrared spectra acquired with vims at 0 025 s intervals during a 74 km altitude flyover of the south pole of enceladus by the cassini spacecraft on 14 april 2012 utc a thermal emission spectrum covering 3 to 5 m wavelengths was detected as the field of view crossed one of the four major fissures baghdad sulcus within 1 km of 82 36s latitude and 28 24w longitude we interpret this spectrum as thermal emission from a linear fissure with temperature 197 20 k and width 9 m at the above wavelengths the spectrum is dominated by the warmest temperature component looking downward into the fissure at only 13 from the vertical we conclude that our results measure the temperature of the interior fissure walls and the h 2 o vapor at depths within 40 m of the surface

compositional maps of saturn s moon phoebe from imaging spectroscopy the origin of phoebe which is the outermost large satellite of saturn is of particular interest because its inclined retrograde orbit suggests that it was gravitationally captured by saturn having accreted outside the region of the solar nebula in which saturn formed by contrast saturn s regular satellites with prograde low inclination circular orbits probably accreted within the sub nebula in which saturn itself formed here we report imaging spectroscopy of phoebe resulting from the cassini huygens spacecraft encounter on 11 june 2004 we mapped ferrous iron bearing minerals bound water trapped co2 probable phyllosilicates organics nitriles and cyanide compounds detection of these compounds on phoebe makes it one of the most compositionally diverse objects yet observed in our solar system it is likely that phoebe s surface contains primitive materials from the outer solar system indicating a surface of cometary origin

albedo and color maps of the saturnian satellites abstract maps of the normal reflectances and color ratios 0 58 0 41 m have been prepared from voyager images for the following saturian satellites mimas enceladus tethys dione and rhea albedo and color variegations on these objects are in general much less than those of the galilean satellites enceladus and mimas have no albedo or color variegations greater than 10 in the observed regions of their surfaces with the exception of a small high albedo area in the southern polar region of enceladus which may be similar to the bright wispy streaks linea on rhea and dione we find an albedo dichotomy of 20 between the leading bright and trailing sides of dione and confirm a similar dichotomy found by verbiscer and veverka icarus 1989 82 336 for rhea this dichotomy is not as marked in the color maps differences of 5 10 were found for the hemispheres of these two satellites unlike the galilean satellites there is little general correlation between color and albedo the only clear example we could find of the expected result that higher albedo surfaces are bluer is for the bright wispy streaks linea on the trailing sides of rhea and dione on tethys we see two lower albedo features the one on the trailing side is redder than the ambient terrain whereas the one on the leading side is bluer there is little correlation between mapped geologic units and features and the color albedo patterns rhea and the trailing side of dione are the only examples where correlations exist the higher albedo photometrically bland leading sides of tethys dione and rhea suggest enhanced erosion of this hemisphere by meteoritic and cometary impact in addition the optical properties of these satellites may be affected by two exogenic processes not considered extensively in previous studies alteration of the surfaces by ultraviolet radiation and accretion of particles from saturn s e ring

albedo dichotomy of rhea hapke analysis of voyager photometry abstract the photometric behavior of rhea s surface has been characterized by fitting hapke s model to both full disk and disk resolved voyager observations the two solutions agree well demonstrating that accurate determinations of hapke parameters are possible from whole disk phase curves provided that extensive phase coverage is available the voyager clear filter eff 0 48 m phase coverage for rhea extends form 1 8 to 135 3 the low phase angle data contain evidence of a measurable opposition effect the high phase angle data allow a good estimate of hapke s large scale roughness parameter 13 and a better determination of the phase integral q 0 78 0 05 and bond albedo ab 0 49 0 06 the hapke analysis shows that the regolith compaction parameter h for rhea is definitely larger more compact regolith than that for titania but is comparable to that of the moon we find evidence of photometric differences other than albedo between the satellite s trailing and leading hemispheres our analysis suggests that the roughness parameter may be smaller for the brighter leading hemisphere than for the darker trailing half of the satellite our final product an albedo map of rhea closely reproduces the satellite s observed lightcurve and indicates that normal reflectances on rhea range from 0 52 near 310 w on the trailing hemisphere to 0 89 at 20 s 80 w on the leading hemisphere the albedo map shows that no terrain or feature in the trailing hemisphere is as bright as any in the leading hemisphere it also demonstrates a striking quasi circular low albedo region centered close to the satellite s anti apex of motion

thermal inertia and bolometric bond albedo values for mimas enceladus tethys dione rhea and iapetus as derived from cassini cirs measurements abstract spectra taken by cassini s composite infrared spectrometer cirs between 10 and 600 cm 1 17 1000 m of surface thermal emission of mimas enceladus tethys dione rhea and iapetus have been used to derive the thermal inertia and bolometric bond albedo values only an upper limit for the bolometric bond albedo of iapetus dark leading side could be determined due to the insensitivity of the thermal model to albedo when albedos are very low the thermal inertia in this region however is better constrained the cirs coverage of enceladus is extensive enough that the latitudinal variation in these values from 60 s to 70 n has been determined in 10 wide bins the bolometric bond albedos determined here are consistent with literature values which show the surface of the saturnian icy moons to be covered in ice contaminated to varying degrees the thermal inertia of the moons is shown to be in the range 9 20 j m 2 k 1 s 1 2 approximately 2 6 times lower than that of the galilean satellites implying a less well consolidated and more porous surface the thermal inertias of iapetus and phoebe are somewhat higher suggesting that the very low thermal inertias of satellites from rhea inwards may be related to their probable coating of e ring material latitudinal variations on the surface of enceladus show that the bolometric bond albedo and thermal inertia increase towards the active plume source at the south pole

dione s spectral and geological properties abstract we present a detailed analysis of the variations in spectral properties across the surface of saturn s satellite dione using cassini vims data and their relationships to geological and or morphological characteristics as seen in the cassini iss images this analysis focuses on a local region on dione s anti saturnian hemisphere that was observed by vims with high spatial resolution during orbit 16 in october 2005 the results are incorporated into a global context provided by vims data acquired within cassini s first 50 orbits our results show that dione s surface is dominated by at least one global process bombardment by magnetospheric particles is consistent with the concentration of dark material and enhanced co 2 absorption on the trailing hemisphere of dione independent of the geology local regions within this terrain indicate a special kind of resurfacing that probably is related to large scale impact process in contrast the enhanced ice signature on the leading side is associated with the extended ejecta of the fresh impact crater creusa 49 n 76 w although no geologically active regions could be identified dione s tectonized regions observed with high spatial resolution partly show some clean h 2 o ice implying that tectonic processes could have continued into more recent times

maps of tethys thermophysical properties on 11th april 2015 cassini s composite infrared spectrometer cirs made a series of observations of tethys daytime anti saturn hemisphere over a nine hour time period during this time the sub spacecraft position was remarkably stable 0 3 s to 3 9 s 153 2 w to 221 8 w and so these observations provide unprecedented coverage of diurnal temperature variations on tethys anti saturn hemisphere in 2012 a thermal anomaly was discovered at low latitudes on tethys leading hemisphere it appears cooler during the day and warmer at night than its surroundings howett et al 2012 and is spatially correlated with a decrease in the ir3 uv3 visible color ratio schenk et al 2011 the cause of this anomaly is believed to be surface alteration by high energy electrons which preferentially bombard low latitudes of tethys leading hemisphere schenk et al 2011 howett et al 2012 paranicas et al 2014 schaible et al 2017 the thermal anomaly was quickly dubbed pac man due to its resemblance to the 1980s video game icon we use these daytime 2015 cirs data along with two sets of nighttime cirs observations of tethys from 27 june 2007 and 17 august 2015 to make maps of bolometric bond albedo and thermal inertia variations across the anti saturn hemisphere of tethys including the edge of its pac man region these maps confirm the presence of the pac man thermal anomaly and show that while tethys bolometric bond albedo varies negligibly outside and inside the anomaly 0 69 0 02 inside compared to 0 71 0 04 outside the thermal inertia varies dramatically 29 10 j m 2 k 1 s 1 2 inside compared to 9 4 j m 2 k 1 s 1 2 outside these thermal inertias are in keeping with previously published values 25 3 j m 2 k 1 s 1 2 inside and 5 1 j m 2 k 1 s 1 2 outside the anomaly howett et al 2012 a detailed analysis shows that on smaller spatial scales the bolometric bond albedo does vary increasing to a peak value at 180 w for longitudes between 100 w and 160 w the thermal inertia increases from northern to southern latitudes while the reverse is true for bolometric bond albedo the thermal inertia on tethys generally increases towards the center of its leading hemisphere but also displays other notable small scale variations these thermal inertia and bolometric bond albedo variations are perhaps due to differences in competing surface modification by e ring grains and high energy electrons which both bombard tethys leading hemisphere but in different ways a comparison between the observed temperatures and our best thermal model fits shows notable discrepancies in the morning warming curve which may provide evidence of regional variations in surface roughness effects perhaps again due to variations in surface alteration mechanisms

saturn s icy satellites investigated by cassini vims ii results at the end of nominal mission abstract we report the detailed analysis of the spectrophotometric properties of saturn s icy satellites as derived by full disk observations obtained by visual and infrared mapping spectrometer vims experiment aboard cassini in this paper we have extended the coverage until the end of the cassini s nominal mission june 1st 2008 while a previous paper filacchione g and 28 colleagues 2007 icarus 186 259 290 hereby referred to as paper i reported the preliminary results of this study during the four years of nominal mission vims has observed the entire population of saturn s icy satellites allowing us to make a comparative analysis of the vis nir spectral properties of the major satellites mimas enceladus tethys dione rhea hyperion iapetus and irregular moons atlas prometheus pandora janus epimetheus telesto calypso phoebe the results we discuss here are derived from the entire dataset available at june 2008 which consists of 1417 full disk observations acquired from a variety of distances and inclinations from the equatorial plane with different phase angles and hemispheric coverage the most important spectrophotometric indicators as defined in paper i i f continua at 0 55 m 1 822 m and 3 547 m visible spectral slopes water and carbon dioxide bands depths and positions are calculated for each observation in order to investigate the disk integrated composition of the satellites the distribution of water ice respect to contaminants abundances and typical regolith grain properties these quantities vary from the almost pure water ice surfaces of enceladus and calypso to the organic and carbon dioxide rich hyperion iapetus and phoebe janus visible colors are intermediate between these two classes having a slightly positive spectral slope these results could help to decipher the origins and evolutionary history of the minor moons of the saturn s system we introduce a polar representation of the spectrophotometric parameters as function of the solar phase angle along radial distance and of the effective longitude interval illuminated by the sun and covered by vims during the observation in azimuth to better investigate the spatial distribution of the spectrophotometric quantities across the regular satellites hemispheres finally we report the observed spectral positions of the 4 26 m band of the carbon dioxide present in the surface material of three outermost moons hyperion iapetus and phoebe

formation of iapetus extreme albedo dichotomy by exogenically triggered thermal ice migration the striking appearance of saturn s moon iapetus half black and half white has puzzled astronomers for over three centuries now spencer and denk p 432 1 published online 10 december present an explanation for this asymmetry a thermally controlled runaway migration of water ice triggered by exogenic deposition of dark material on the moon s leading darker side which faces the direction of motion of the moon in its orbit around saturn this mechanism is unique to iapetus because it rotates slowly enough to allow large temperature variations to arise it is small enough to allow long range migration of water and there is a source of dust to trigger the process in a related paper denk et al p 435 2 published online 10 december present data derived from the cassini imaging science subsystem that reveal that both dark and bright materials on the leading side of iapetus are redder than their trailing side counterparts this asymmetry results from the deposition of dust and debris from other moons in the saturnian system the very same process that initiates the thermal segregation proposed above 1 lookup doi 10 1126 science 1177132 2 lookup doi 10 1126 science 1177088

photometrically corrected global infrared mosaics of enceladus new implications for its spectral diversity and geological activity between 2004 and 2017 spectral observations have been gathered by the visual and infrared mapping spectrometer vims on board cassini brown et al 2004 during 23 enceladus close encounters in addition to more distant surveys the objective of the present study is to produce a global hyperspectral mosaic of the complete vims data set of enceladus in order to highlight spectral variations among the different geological units this requires the selection of the best observations in terms of spatial resolution and illumination conditions we have carried out a detailed investigation of the photometric behavior at several key wavelengths 1 35 1 5 1 65 1 8 2 0 2 25 2 55 and 3 6 m characteristics of the infrared spectra of water ice we propose a new photometric function based on the model of shkuratov et al 2011 when combined corrected mosaics at different wavelengths reveal heterogeneous areas in particular in the terrains surrounding the tiger stripes on the south pole and in the northern hemisphere around 30 n 90 w those areas appear mainly correlated to tectonized units indicating an endogenous origin potentially driven by seafloor hotspots

distribution of icy particles across enceladus surface as derived from cassini vims measurements abstract the surface of enceladus consists almost completely of water ice as the band depths of water ice absorptions are sensitive to the size of particles absorptions can be used to map variations of icy particles across the surface the visual and infrared mapping spectrometer vims observed enceladus with a high spatial resolution during three cassini flybys in 2005 orbits en 003 en 004 and en 011 based on these data we measured the band depths of water ice absorptions at 1 04 1 25 1 5 and 2 m these band depths were compared to water ice models that represent theoretically calculated reflectance spectra for a range of particle diameters between 2 m and 1 mm the agreement between the experimental vims and model values supports the assumption that pure water ice characterizes the surface of enceladus and therefore that variations in band depth correspond to variations in water ice particle diameters our measurements show that the particle diameter of water ice increases toward younger tectonically altered surface units with the largest particles exposed in relatively fresh surface material the smallest particles were generally found in old densely cratered terrains the largest particles 0 2 mm are concentrated in the so called tiger stripes at the south pole in general the particle diameters are strongly correlated with geologic features and surface ages indicating a stratigraphic evolution of the surface that is caused by cryovolcanic resurfacing and impact gardening

deciphering sub micron ice particles on enceladus surface the surface of saturn s moon enceladus is composed primarily by pure water ice the cassini spacecraft has observed present day geologic activity at the moon s south polar region related with the formation and feeding of saturn s e ring plumes of micron sized particles composed of water ice and other non ice contaminants e g co2 nh3 ch4 erupt from four terrain s fractures named tiger stripes some of this material falls back on enceladus surface to form deposits that extend to the north at 40 w and 220 w with the highest concentration found at the south pole in this work we analyzed vims ir data to identify plumes deposits across enceladus surface through the variation in band depth of the main water ice spectral features to characterize the global variation of water ice band depths across enceladus the entire surface was sampled with an angular resolution of 1 in both latitude and longitude and for each angular bin we averaged the value of all spectral indices as retrieved by vims the position of the plumes deposits predicted by theoretical models display a good match with water ice band depths maps on the trailing hemisphere whereas they diverge significantly on the leading side space weathering processes acting on enceladus surface ionize and break up water ice molecules resulting in the formation of particles smaller than one micron we also mapped the spectral indices for sub micron particles and we compared the results with the plumes deposits models again a satisfactory match is observed on the trailing hemisphere only finally we investigated the variation of the depth of the water ice absorption bands as a function of the phase angle in the visible range some terrains surrounding the tiger stripes show a decrease in albedo when the phase angle is smaller than 10 this unusual effect cannot be confirmed by near infrared data since observations with a phase angle lower than 10 are not available for phase angle values greater than 10 the depth of the water ice features remains quite constant within a broad range of phase angle values

shrimp u pb zircon geochronology of the liaoji granitoids constraints on the evolution of the paleoproterozoic jiao liao ji belt in the eastern block of the north china craton abstract the paleoproterozoic jiao liao ji belt lies at the eastern margin of the eastern block of the north china craton and is composed mainly of the liaohe group and the liaoji granitoids the liaoji granitoids are divisible into pre tectonic magnetite and hornblende biotite monzogranitic gneisses and post tectonic or anorogenic porphyritic monzogranites and alkaline syenites shrimp u pb zircon geochronology combined with cathodoluminescence cl imaging has enabled for resolution of magmatic and metamorphic events that can be directed towards understanding the history of the paleoproterozoic jiao liao ji belt shrimp u pb zircon analyses reveal that the pre tectonic magnetite monzogranitic gneisses were emplaced in the period 2176 2166 ma and metamorphosed at 1914 ma and the pre tectonic hornblende biotite monzogranitic gneisses were emplaced at 2150 2143 ma these data demonstrate that the pre tectonic monzogranitic gneisses of the liaoji granitoids were not younger than the deposition of the liaohe group as previously considered since the latter contains a large amount of 2100 2000 ma detrital zircons in contrast the pre tectonic monzogranitic gneisses of the liaoji granitoids or similar aged granitoids may have been an important component of the provenance for the liaohe group shrimp u pb zircon analyses also reveal that the post tectonic porphyritic monzogranites and granites in the jiao liao ji belt were emplaced at 1875 10 and 1856 31 ma respectively simultaneously with the emplacement of the alkaline syenites that was dated at 1857 20 and 1843 23 ma similar post tecotnic or anorogenic granites are not only limited to the jiao liao ji belt but are also found in the north and south korea suggesting that the 1 85 ga post tectonic or anorogenic granitic magmatic event may have occurred in both the korean peninsula and the eastern block of the north china craton the shrimp zircon ages of this study combined with lithological structural metamorphic and geochemical data is consistent with a rift closure model which suggests that the archean complexes on the northern and southern sides of the jiao liao ji belt were originally situated on a single continental block that underwent paleoproterozoic rifting associated with the formation of the liaohe group and liaoji granitoids and closed upon itself at 1 9 ga

spectroscopic classification of icy satellites of saturn ii identification of terrain units on rhea abstract dione is one of the largest and densest icy satellites of saturn its surface shows a marked asymmetry between its leading and trailing hemispheres the leading side being brighter than the trailing side which shows regions mantled by a dark veneer whose origin is likely exogenic in order to identify different terrain units we applied the spectral angle mapper sam classification technique to dione s hyperspectral images acquired by the visual and infrared mapping spectrometer vims onboard the cassini orbiter in the infrared range 0 88 5 12 m on a relatively limited portion of the surface of dione we first identified nine spectral endmembers corresponding to as many terrain units which mostly distinguish for water ice abundance and ice grain size we then used these endmembers in sam to achieve a comprehensive classification of the entire surface the analysis of the infrared spectra returned by vims shows that different regions of dione have variations in water ice bands depths in average ice grain size and in the concentration of contaminants such as co 2 and hydrocarbons which are clearly connected to morphological and geological structures generally the spectral units that classify optically dark terrains are those showing suppressed water ice bands a finer ice grain size and a higher concentration of carbon dioxide conversely spectral units labeling brighter regions have deeper water ice absorption bands higher albedo and a smaller concentration of contaminants we also considered vims cubes of the small satellite helene one of the two dione s trojan moons and we compared its infrared spectra to those of the spectral units found on dione we observe that the closest match between the spectra of the two satellites occurs for one of the youngest and freshest terrain units on dione the creusa crater region

finding the trigger to iapetus odd global albedo pattern dynamics of dust from saturn s irregular satellites abstract the leading face of saturn s moon iapetus cassini regio has an albedo only one tenth that on its trailing side the origin of this enigmatic dichotomy has been debated for over 40 years but with new data a clearer picture is emerging motivated by cassini radar and imaging observations we investigate soter s model of dark exogenous dust striking an originally brighter iapetus by modeling the dynamics of the dark dust from the ring of the exterior retrograde satellite phoebe under the relevant perturbations in particular we study the particles probabilities of striking iapetus as well as their expected spatial distribution on the iapetian surface we find that of the long lived particles 5 m most particle sizes 10 m are virtually certain to strike iapetus and their calculated distribution on the surface matches up well with cassini regio s extent in its longitudinal span the satellite s polar regions are observed to be bright presumably because ice is deposited there thus in the latitudinal direction we estimate polar dust deposition rates to help constrain models of thermal migration invoked to explain the bright poles spencer j r denk t 2010 science 327 432 435 we also analyze dust originating from other irregular outer moons determining that a significant fraction of that material will eventually coat iapetus perhaps explaining why the spectrum of iapetus dark material differs somewhat from that of phoebe finally we track the dust particles that do not strike iapetus and find that most land on titan with a smaller fraction hitting hyperion as has been previously conjectured such exogenous dust coupled with hyperion s chaotic rotation could produce hyperion s roughly isotropic moderate albedo surface

cassini observes the active south pole of enceladus cassini has identified a geologically active province at the south pole of saturn s moon enceladus in images acquired by the imaging science subsystem iss this region is circumscribed by a chain of folded ridges and troughs at 55 s latitude the terrain southward of this boundary is distinguished by its albedo and color contrasts elevated temperatures extreme geologic youth and narrow tectonic rifts that exhibit coarse grained ice and coincide with the hottest temperatures measured in the region jets of fine icy particles that supply saturn s e ring emanate from this province carried aloft by water vapor probably venting from subsurface reservoirs of liquid water the shape of enceladus suggests a possible intense heating epoch in the past by capture into a 1 4 secondary spin orbit resonance

temporal variations in latest quaternary slip across the australian pacific plate boundary northeastern south island new zealand rates of latest quaternary slip from stream terraces and moraines displaced by faults of the alpine shear system in ne south island new zealand vary in space and time detailed histories of fault slip are obtained from combining displacement data with estimates of the age of the surface from weathering characteristics precision in surface ages is 5 20 using rock weathering rinds and 15 50 using soil properties the oldest surfaces examined are 15 20 ka and have right lateral fault offsets up to 400 600 m the main faults of the in the ne south island the wairau awatere clarence hope kekerengu and porters pass faults have average latest quaternary right lateral slip rates of 3 10 5 10 7 10 25 40 5 7 and 3 4 mm yr respectively every fault has undergone a substantial decrease in lateral slip rate in the last 3 5 kyr summed across the plate boundary the average latest quaternary slip rates are comparable to long term rates of horizontal slip across the australian pacific plate boundary around 40 mm yr parallel to the boundary and rates of geodetic strain and seismic moment release over the last 50 100 years approximately the same however sums of lateral fault slip rates over the interval from 15 to 5 ka exceed the plate motions whereas late holocene lateral fault slip rates are less than half the long term average the best explanation of these variations is slip across the plate boundary is episodic varying over perhaps 5 kyr intervals this implies that 15 20 kyr is the time interval necessary to average out shorter 5 kyr episodic variations in plate boundary motions

surface composition of hyperion hyperion saturn s eighth largest icy satellite is a body of irregular shape in a state of chaotic rotation the surface is segregated into two distinct units a spatially dominant high albedo unit having the strong signature of h2o ice contrasts with a unit that is about a factor of four lower in albedo and is found mostly in the bottoms of cup like craters here we report observations of hyperion s surface in the ultraviolet and near infrared spectral regions with two optical remote sensing instruments on the cassini spacecraft at closest approach during a fly by on 25 26 september 2005 the close fly by afforded us the opportunity to obtain separate reflectance spectra of the high and low albedo surface components the low albedo material has spectral similarities and compositional signatures that link it with the surface of phoebe and a hemisphere wide superficial coating on iapetus

saturn s icy satellites investigated by cassini vims iv daytime temperature maps abstract the spectral position of the 3 6 m continuum peak measured on cassini vims i f spectra is used as a marker to infer the temperature of the regolith particles covering the surfaces of saturn s icy satellites this feature is characterizing the crystalline water ice spectrum which is the dominant compositional endmember of the satellites surfaces laboratory measurements indicate that the position of the 3 6 m peak of pure water ice is temperature dependent shifting towards shorter wavelengths when the sample is cooled from about 3 65 m at t 123 k to about 3 55 m at t 88 k a similar method was already applied to vims saturn s rings mosaics to retrieve ring particles temperature filacchione g ciarniello m capaccioni f et al 2014 icarus 241 45 65 we report here about the daytime temperature variations observed on the icy satellites as derived from three different vims observation types a a sample of 240 disk integrated i f observations of saturn s regular satellites collected by vims during years 2004 2011 with solar phase in the 20 40 range corresponding to late morning early afternoon local times this dataset is suitable to exploit the temperature variations at hemispherical scale resulting in average temperature t t 88 k for enceladus t t 98 118 k for dione t 108 128 k for rhea t 118 128 k for hyperion t 128 148 and t 168 k for iapetus trailing and leading hemispheres respectively a typical 5 k uncertainty is associated to the temperature retrieval on tethys and dione for which observations on both leading and trailing hemispheres are available in average daytime temperatures higher of about 10 k on the trailing than on the leading hemisphere are inferred b satellites disk resolved observations taken at 20 40 km pixel 1 resolution are suitable to map daytime temperature variations across surfaces features such as enceladus tiger stripes and tethys equatorial dark lens these datasets allow to disentangle solar illumination conditions from temperature distribution when observing surface s features with strong thermal contrast c daytime average maps covering large regions of the surfaces are used to compare the inferred temperature with geomorphological features impact craters chasmatae equatorial radiation lenses and active areas and albedo variations temperature maps are built by mining the complete vims dataset collected in years 2004 2009 pre equinox and in 2009 2012 post equinox by selecting pixels with max 150 km pixel 1 resolution vims derived temperature maps allow to identify thermal anomalies across the equatorial lens of mimas and tethys a temperature t 115k is measured above enceladus damascus and alexandria sulci in the south pole region vims has the sensitivity to follow seasonal temperature changes on tethys dione and rhea higher temperature are measured above the south hemisphere during pre equinox and above the north hemisphere during post equinox epochs the measured temperature distribution appears correlated with surface albedo features in fact temperature increases on low albedo units located on tethys dione and rhea trailing hemispheres the thermal anomaly region on rhea s inktomi crater detected by cirs howett c j a spencer j r hurford t et al 2014 icarus 241 239 247 is confirmed by vims this area appears colder with respect to surrounding terrains when observed at the same local solar time

petrogenesis of the 2090 ma zanhuang ring and sill complexes in north china a bimodal magmatism related to intra continental process abstract it is widely debated as to whether the 2100 ma bimodal magmatic events in the eastern north china craton represent intra continental rifting or marginal processes the genetic relationship between the two components of bimodal suites is the key solution to this issue and this is investigated on a group of newly identified ring complexes as well as the apparently associated sills in zanhuang southern taihang mts these ring complexes comprise varied components pyroxenite gabbro anorthosite k rich a type granite and minor na rich a type granite u pb analyses on baddeleyite and zircon grains liberated from a gabbro sample both yield a 2090 ma age which represents crystallization timing and is contemporaneous with a type granites of the ring complexes as well as the sills in the gantaohe group the mafic rocks of the ring complexes and sills show similar chemical features they were characterized by enriched light rare earth elements compared to middle and heavy ones la ybn 1 4 2 8 enriched large lithosphile elements but depleted high field strength elements and enriched sr nd isotopes endt t 2090 ma 1 9 0 6 nd tdm 2 7 ga they were most likely originated from the same magma source resided in the sub continental lithospheric mantle which formed in the late archean the compositional variation of the mafic sills may be resulted from the fractionation of olivine and plagioclase the k rich a type granite as well as the dacitic sills could be originated from this same source with firstly olivine plagioclase dominated fractionation in the lower magma chamber to more felsic compositions and then with significant removal of clinopyroxene plagioclase in the upper magma chamber which at the same time produced pyroxenite gabbro and minor anorthosite cumulates in the ring complexes na rich a type granite was likely formed locally under relatively high water fugacity with fractionation of k feldspar plagioclase clinopyroxene from a parental magma similar to the k rich a type granite this bimodal zanhuang ring and sill complexes and other comparable bimodal suites widely distributed in the eastern north china craton were likely intra continental representing a craton scale extension at 2100 ma

two episodes of paleoproterozoic mafic intrusions from liaoning province north china craton petrogenesis and tectonic implications abstract mafic dyke swarms constitute a common occurrence within the cratonic provinces in the world since the archean proterozoic boundary and their geneses harbor critical information for facilitating regional tectonic and supercontinental reconstruction this zircon u pb dating and geochemical study documents two episodes of paleoproterozoic mafic intrusions from liaoning province north china craton ncc the haicheng suite hcs with an emplacement age of ca 2125 ma from the liaodong peninsula and the guohua suite ghs with an age of ca 1816 ma from the western liaoning terrane the hcs meta gabbros are tholeiitic in composition with an sio 2 range from 46 to 52 modest enrichment in light rare earth elements lree and depletion in high field strength elements hfse and possess radiogenic whole rock nd nd t 1 91 to 4 21 and zircon hf hf t 4 02 to 8 48 isotopic compositions these features endow the hcs with a juvenile subduction fluid metasomatized lithospheric mantle source by contrast the ghs exhibits a meta gabbroic to dioritic composition and a transitional character from tholeiitic to calc alkali with variably enriched lrees and more evolved isotopic signatures nd t 0 20 to 5 82 zircon hf t 0 09 to 4 91 than the hcs while the relatively intact high fe gabbroic samples are supposed to represent partial melts from a fertile cratonic sub continental lithospheric mantle source in the garnet spinel stability field the low fe dioritic ones tend to bear the imprints of subsequent assimilation and fractional crystallization process apart from making an important contribution to the present archive of the paleoproterozoic mafic dyke swarms in the ncc the present two mafic magmatic suites witnessed a shift in tectonic setting from a subduction related continental arc environment to a post orogenic extensional regime synthesizing two suites with coeval felsic igneous episodes as well as concomitant episodic metamorphic events in the jiao liao ji belt leads to the characterization of a possible divergent double subduction system in the eastern ncc during the time span of ca 2 2 1 80 ga synchronized beating of episodic magmatic and metamorphic pulses in the constituent mobile belts of the ncc carries further implication of attesting to the ubiquity and importance of divergent double subduction system in the cratonic amalgamation and its incorporation within the supercontinent columbia

saturn s icy satellites and rings investigated by cassini vims iii radial compositional variability in the last few years cassini vims the visible and infrared mapping spectrometer returned to us a comprehensive view of the saturn s icy satellites and rings after having analyzed the satellites spectral properties filacchione g capaccioni f mccord t b coradini a cerroni p bellucci g tosi f d aversa e formisano v brown r h baines k h bibring j p buratti b j clark r n combes m cruikshank d p drossart p jaumann r langevin y matson d l mennella v nelson r m nicholson p d sicardy b sotin c hansen g hibbitts k showalter m newman s 2007 icarus 186 259 290 paper i and their distribution across the satellites hemispheres filacchione g capaccioni f clark r n cuzzi j n cruikshank d p coradini a cerroni p nicholson p d mccord t b brown r h buratti b j tosi f nelson r m jaumann r stephan k 2010 icarus 206 507 523 paper ii we proceed in this paper to investigate the radial variability of icy satellites principal and minor and main rings average spectral properties this analysis is done by using 2264 disk integrated observations of the satellites and a 12 700 pixels wide rings radial mosaic acquired with a spatial resolution of about 125 km pixel using different vis and ir spectral indicators e g spectral slopes and band depths we perform a comparative analysis of these data aimed to measure the distribution of water ice and red contaminant materials across saturn s system the average surface regolith grain sizes are estimated with different indicators through comparison with laboratory and synthetic spectra these measurements highlight very striking differences in the population here analyzed which vary from the almost uncontaminated and water ice rich surfaces of enceladus and calypso to the metal organic rich and red surfaces of iapetus leading hemisphere and phoebe rings spectra appear more red than the icy satellites in the visible range but show more intense 1 5 2 0 m band depths although their orbits are close to the f ring prometheus and pandora are different in surface composition prometheus in fact appears very water ice rich but at the same time very red at vis wavelengths these properties make it very similar to a b ring particles while pandora is bluer moving outwards we see the effects of e ring particles generated by enceladus plumes which contaminate satellites surfaces from mimas out to rhea we found some differences between tethys lagrangian moons calypso being much more water ice rich and bluer than telesto among outer satellites hyperion iapetus and phoebe we observe a linear trend in both water ice decrease and in reddening hyperion being the reddest object of the population the correlations among spectral slopes band depths visual albedo and phase permit us to cluster the saturnian population in different spectral classes which are detected not only among the principal satellites and rings but among co orbital minor moons as well these bodies are effectively the connection elements both in term of composition and evolution between the principal satellites and main rings finally we have applied hapke s theory to retrieve the best spectral fits to saturn s inner regular satellites from mimas to dione using the same methodology applied previously for rhea data discussed in ciarniello et al ciarniello m capaccioni f filacchione g clark r n cruikshank d p cerroni p coradini a brown r h buratti b j tosi f stephan k 2011 icarus 214 541 555

iapetus surface variability revealed from statistical clustering of a vims mosaic the distribution of co2 abstract we present a detailed study of an iapetus mosaic of vims data with high spatial resolution 0 5 0 5 or 6 4 km pixel the spectra were taken in august 2007 and provide the highest vims spatial resolution data for this object during cassini s primary mission we analyze this set of data using a statistical clustering approach to reduce the analysis of a large number of data 10 4 spectra from 0 35 to 5 10 m to the study of seven representative groups accounting for 99 6 of the surface covered by the original sample we analyze the spectral absorption bands in the spectra of the different clusters indicative of different composition over the observed surface we find coherence between the distribution of the clusters and the geographical features on the surface we give special attention to the study of the water ice and co 2 bands we find that co 2 is widespread over the entire surface being studied including the bright and dark areas on iapetus surface and is probably trapped at the molecular level with other materials the strength of the co 2 band in the areas where both h 2 o and carbon bearing materials exist gives support to the hypothesis that this volatile is formed on the surface of iapetus as a product of irradiation of these two components finally we also compare the iapetus co 2 with that on other satellites confirming that there are evident differences on the center depth and width of the band on iapetus and phoebe where co 2 has been suggested to be endogenous

iapetus near surface thermal emission modeled and constrained using cassini radar radiometer microwave observations abstract since its arrival at saturn the cassini spacecraft has had only a few opportunities to observe iapetus saturn s most distant regular satellite these observations were all made from long ranges 100 000 km except on september 10 2007 during cassini orbit 49 when the spacecraft encountered the two toned moon during its closest flyby so far in this pass it collected spatially resolved data on the object s leading side mainly over the equatorial dark terrains of cassini regio cr in this paper we examine the radiometry data acquired by the cassini radar during both this close targeted flyby referred to as ia49 3 and the distant iapetus observations in the radar s passive mode the receiver functions as a radiometer to record the thermal emission from planetary surfaces at a wavelength of 2 2 cm on the cold icy surfaces of saturn s moons the measured brightness temperatures depend both on the microwave emissivity and the physical temperature profile below the surface down to a depth that is likely to be tens of centimeters or even a few meters combined with the concurrent active data passive measurements can shed light on the composition structure and thermal properties of planetary regoliths and thus on the processes from which they have formed and evolved the model we propose for iapetus microwave thermal emission is fitted to the ia49 3 observations and reveals that the thermal inertias sensed by the cassini radiometer over both cr and the bright mid to high latitude terrains namely ronceveaux terra rt in the north and saragossa terra st in the south significantly exceed those measured by cassini s cirs composite infrared spectrometer which is sensitive to much smaller depths generally the first few millimeters of the surface this implies that the subsurface of iapetus sensed at 2 2 cm wavelength is more consolidated than the uppermost layers of the surface in the case of cr a thermal inertia of at least 50 j m 2 k 1 s 1 2 and most probably 200 j m 2 k 1 s 1 2 is inferred this suggests a gradient in density with depth or more likely that the radiometer has probed the icy substrate underlying the dark layer furthermore the measured thermal emission is found to arise from the upper few meters of the subsurface which points to tholins rather than iron oxide compounds as the primary contaminants of the dark material we also find that although there is a latitudinal decrease probably related to the thinning of the dark layer away from the equator the cr region exhibits a high 2 2 cm emissivity 0 87 in average which is close to the emissivity of phoebe a putative source of the dark matter in the case of rt st model fitting points to a mean thermal inertia of 160 j m 2 k 1 s 1 2 along with the possible presence of an absorbing compound in the regolith of the bright terrains nevertheless this layer is transparent enough for the radiometer to capture the seasonal contrast between the northern and southern hemispheres lastly a global decline of the microwave emissivity with latitude is revealed it is probably indicative of a progressive increase of the water ice content in the near surface