analysis of cassini cirs limb spectra of titan acquired during the nominal mission i hydrocarbons nitriles and co2 vertical mixing ratio profiles observations of the composite infrared spectrometer cirs during the entire nominal cassini mission 2004 2008 provide us with an accurate global view of composition and temperature in the middle atmosphere of titan between 100 and 500 km we investigated limb spectra acquired at 0 5 cm 1 resolution at nine different latitudes between 56 s and 80 n with a better sampling in the northern hemisphere where molecular abundances and temperature present strong latitudinal variations from this limb data acquired between february 2005 and may 2008 we retrieved the vertical mixing ratio profiles of c2h2 c2h4 c2h6 c3h8 ch3c2h c4h2 c6h6 hcn hc3n and co2 we present here for the first time the latitudinal variations of the c2h6 c3h8 co2 c2h4 and c6h6 vertical mixing ratios profiles some molecules such as c2h6 or c3h8 present little variations above their condensation level the other molecules except co2 show a significant enhancement of their mixing ratios poleward of 50 n c2h4 is the only molecule whose mixing ratio decreases with height at latitudes below 46 n regions depleted in c2h2 hcn and c4h2 are observed around 400 km 0 01 mbar and 55 n we also inferred a region enriched in co2 located between 30 and 40 n in the 2 0 7 mbar pressure range at 80 n almost all molecules studied here present a local minimum of their mixing ratio profiles near 300 km 0 07 mbar which is in contradiction with global circulation models that predict constant with height vertical profiles due to subsidence at the north pole 2009 elsevier inc all rights reserved

low temperature aqueous alteration of basalt mineral assemblages of deccan basalts and implications for mars spectra of basalt samples were dominated by fe 2 crystal field transitions with weak alteration bands near 1 4 and or 1 9 mm reststrahlen bands in mid infrared showed the convolution of plagioclase and pyroxene features typical of basalts saprolite samples were incompletely leached and their spectra were dominated by complex al and fe mg bearing smectite clays and retained no original mafic signatures xrd and mossbauer detected pyroxene and plagioclase not visible by reflectance spectroscopy in some saprolite samples zeolites were present throughout the saprolite the laterite was the most leached horizon and all analyses showed kaolinite and iron oxide assemblages this kaolinite and hematite association would be expected if kaolinite on mars formed through leaching under conditions similar to those on earth and has implications for abundant freshwater on the martian surface

numerical simulation of tides and oceanic angular momentum of titan s hydrocarbon seas abstract tides and tidal currents in titan s hydrocarbon seas are numerically simulated by a 3 dimensional ocean circulation model using a bathymetry map constrained by cassini these predictions are used to calculate the tidally induced variations of the oceanic angular momentum of the seas the tides behave as a quasi standing wave with anti nodes at the northern and southern shores the tidal currents in kraken mare are mainly oriented along the major axis of the sea and are dominated by fast hydraulic currents through a narrow strait the axial oceanic angular momentum primarily changes due to redistribution of liquids in kraken mare and maximizes when there is ebb at the northern shore and flood at the southern shore on the other hand variations of the equatorial oceanic angular momentum are contributed by both tides and tidal currents the oceanic torque between sea and sea bottom is minor compared to its atmospheric counterpart i e the mountain torque between atmosphere and mountains

observations of overturning in the thermocline the context of ocean mixing abstract the time sequence of events that lead to internal wave breaking and ocean turbulence is investigated data are obtained from depths 100 400 m with a repeat profiling ctd and a coded pulse doppler sonar the instruments were deployed from r p flip during february march 1995 while stationed 30 km west of point arguello california as an aspect of the marine boundary layer experiment although the water depth at the site is 1500 m both rms shear and diapycnal diffusivity as inferred from the average rate and size of overturning events increase with depth below 250 m a deep source of wave energy is implied depth time series of 6 4 m shear s 2 m strain n2 n2 where n is the buoyancy frequency 6 4 m gradient richardson number ri n2 s2 and 2 m effective strain rate the depth derivative of ctd inferred vertical velocity are obtained at 4 minute intervals over a 9 day 100 400 m domain the occurrence of overturns static instabilities of vertical scale 2 m in the observed density

characterization of titan s ontario lacus region from cassini vims observations abstract liquid hydrocarbons were long predicted on titan s surface before the radar instrument onboard cassini detected lakes poleward of 70 n in july 2006 before that the cassini imaging science subsystem iss observed a lake like feature in the south pole named ontario lacus in july 2004 here we analyze one observation of ontario lacus taken by the visual and infrared mapping spectrometer vims on 2007 december 5 during the t 38 flyby this is the best spatially resolved image of a titan lake to date by an imaging spectrometer and has been previously reported in brown et al brown r h soderblom l a soderblom j m clark r n jaumann r barnes j w sotin c buratti b baines k h nicholson p d 2008 nature 454 607 610 and in barnes et al barnes j w et al 2009 icarus 201 217 225 the observing geometry and our data processing will be explained followed by a discussion of the main characteristics of the image the analyzed image covers a small portion of ontario lacus and shows what appears from radar data to be a region of modest slope ramp adjacent to the dark lake itself our analysis of 5 0 m spectral data suggests that the previously reported absorption feature of ethane seen at shorter wavelengths may be produced by damp sediments adjacent to the main liquid basin the latter appears to be absorbing all of the photons incident upon it in the 5 m spectral region and shows no discernible absorption features a characterization of the basin composition and morphology is developed with the help of iss and radar observations the simplest model consistent with the data is an optically deep lake surrounded by a region in which ethane propane possibly methane and other less volatile hydrocarbons and nitriles are present mixed into spectroscopically neutral sediments the dominance of relatively low vapor pressure organics outside the lake itself suggests a retreat of ontario lacus associated with evaporation on seasonal or longer timescales consistent with analysis of radar and iss images

structure of titan s evaporites abstract numerous geological features that could be evaporitic in origin have been identified on the surface of titan although they seem to be water ice poor their main properties chemical composition thickness stratification are essentially unknown in this paper which follows on a previous one focusing on the surface composition cordier d barnes j w ferreira a g 2013b icarus 226 2 1431 1437 we provide some answers to these questions derived from a new model this model based on the up to date thermodynamic theory known as pc saft has been validated with available laboratory measurements and specifically developed for our purpose 1 d models confirm the possibility of an acetylene and or butane enriched central layer of evaporitic deposit the estimated thickness of this acetylene butane layer could explain the strong radar brightness of the evaporites the 2 d computations indicate an accumulation of poorly soluble species at the deposit s margin among these species hcn or aerosols similar to tholins could play a dominant role our model predicts the existence of chemically trimodal bathtub rings which is consistent with what it is observed at the south polar lake ontario lacus this work also provides plausible explanations to the lack of evaporites in the south polar region and to the high radar reflectivity of dry lakebeds

turbulent vertical kinetic energy in the ocean mixed layer abstract vertical velocities in the ocean boundary layer were measured for two weeks at an open ocean wintertime site using neutrally buoyant floats simultaneous measurements of the surface meteorology and surface waves showed a large variability in both wind and wave properties and only weak correlations between them buoyancy forcing was weak the mean square vertical velocity in the boundary layer 2w measured from the vertical motion of the floats was proportional to the squared friction velocity u2 estimated from shipboard meteorological measurements using bulk formulas thus 2w au2 the rate of momentum transport from the atmosphere to the ocean is u2 where is the density of the water the deviations from this relation can be attributed entirely to statistical variation and measurement error the measured values of 2w were corrected for measurement biases and the nonturbulent contributions of internal waves the value of the turbulent part of a is 1 75 2 times that measured in laborato

the lakes of titan the surface of saturn s haze shrouded moon titan has long been proposed to have oceans or lakes on the basis of the stability of liquid methane at the surface1 2 initial visible3 and radar4 5 imaging failed to find any evidence of an ocean although abundant evidence was found that flowing liquids have existed on the surface5 6 here we provide definitive evidence for the presence of lakes on the surface of titan obtained during the cassini radar flyby of titan on 22 july 2006 t16 the radar imaging polewards of 70 north shows more than 75 circular to irregular radar dark patches in a region where liquid methane and ethane are expected to be abundant and stable on the surface2 7 the radar dark patches are interpreted as lakes on the basis of their very low radar reflectivity and morphological similarities to lakes including associated channels and location in topographic depressions some of the lakes do not completely fill the depressions in which they lie and apparently dry depressions are present we interpret this to indicate that lakes are present in a number of states including partly dry and liquid filled these northern hemisphere lakes constitute the strongest evidence yet that a condensable liquid hydrological cycle is active in titan s surface and atmosphere in which the lakes are filled through rainfall and or intersection with the subsurface liquid methane table

space weathering by simulated micrometeorite bombardment on natural olivine and pyroxene a coordinated ir and tem study abstract we studied space weathering effects caused by micrometeorite bombardment simulated by pulsed intense infrared laser generating 15 mj per pulse in high vacuum for our investigation we selected a natural olivine san carlos olivine fo91 and a natural pyroxene bamble orthopyroxene en87 as important rock forming minerals of the earth upper mantle as well as key planetary minerals irradiated areas of powdered pressed samples were examined by optical reflection spectroscopy in a broad optical and infrared wavelength range visible near and mid infrared and transmission electron microscopy to identify changes due to micrometeorite impacts the present study aims to investigate especially the effects of micrometeorite bombardment on reflectance spectra in the mid ir in preparation for future space missions as well as for the mertis experiment onboard the bepicolombo mission for both irradiated samples we found a reduction in albedo and in the reflectance of characteristic reststrahlen bands and an increase of the transparency feature vis and nir spectra of both minerals show the typical darkening and reddening as described for other space weathered samples tem studies revealed that space weathered layers in olivine and pyroxene differ in their respective thickness 450 nm in olivine 100 250 nm in pyroxene as well as in developed nanostratigraphy of laser ablated material like nanophase iron npfe in conclusion our spectral and structural findings were compared to samples in which space weathering was caused by different processes a comparison with these data demonstrates that there is no difference in optical reflectance spectroscopy but a significant difference in the microstructure of minerals due to the weathering source in space as there are solar wind and solar flares cause other structural and chemical changes as the bombardment with micrometeorites

effects of glass content and oxidation on the spectra of snc like basalts applications to mars remote sensing 1 we have investigated the effects of crystallization and oxidation on the visible and near infrared visnir and mid infrared mid ir spectra of materials with a shergotty nakhla chassigny snc basaltic composition in order to investigate potential links between martian visnir spectra martian mid ir spectra and snc meteorite data snc basalt samples of varying crystallinities were synthesized and subsequently oxidized in air at 700 c for 1 7 days and reflectance spectra of both fine 75 m and coarse 75 500 m basalt samples were obtained before and after oxidation the effects of crystallization on the spectral properties are readily observed in the unoxidized products in the visnir increasing crystallization is accompanied by an increasing influence of pyroxene absorptions and decreasing influence of glass absorptions in the mid ir changes in spectral properties with crystallization are due to the variations in relative amounts of glass pyroxene and plagioclase oxidation alters the glass and pyroxenes within the samples leading to changes in visnir and mid ir spectral shapes although distinct signatures of oxidation products are not always observed both spectral and electron microscopy data indicate that hematite is the dominant oxidation product in the pigeonite and glass of the samples in pigeonite hematite is present in nanophase form and leads to the diminishment of the diagnostic 1 and 2 m pyroxene absorptions in the visnir as well as pyroxene absorptions expressed between 800 and 1100 cm 1 in the mid ir in glass hematite forms a near surface layer that is detected with varying efficiencies in the visnir and mid ir depending on the crystallinity and particle size of the analyzed sample oxidized snc basalt samples of various crystallinities and fine grain sizes provide the best analogs to mars remote sensing data in the visnir and mid ir in the visnir partially crystalline oxidized snc basalts can reproduce martian dark region characteristics in the mid ir similarities exist between the spectra of a partially crystalline oxidized snc basalt and the basalt lithology detected by the thermal emission spectrometer tes the andesite lithology detected by tes is best matched by the spectrum of a fully crystalline oxidized snc basalt these results imply that plagioclase rich lithologies are not required by tes data and that observed variations in spectral character of dark regions across the martian surface can be explained by snc basalts influenced by oxidation coupled with variations in degree of crystallization

the lunar rock and mineral characterization consortium deconstruction and integrated mineralogical petrologic and spectroscopic analyses of mare basalts the lunar rock and mineral characterization consortium lrmcc has conducted coordinated mineralogy petrography spectroscopy analyses of a suite of pristine lunar basalts four basalt slabs two low ti two high ti and paired thin sections were analyzed thin sections were analyzed for mineralogy petrography while the slabs were used to prepare particulate separates of major mineral phases and bulk samples mineral separates and particulate bulk samples were crushed to controlled grain sizes and their reflectance spectra measured in the nasa relab at brown university the resulting data set provides an essential foundation for spectral mixing models offers valuable endmember constraints for space weathering analyses and represents critical new ground truth results for lunar science and exploration efforts

radar bright channels on titan abstract during cassini s t44 flyby of titan may 28 2008 the cassini sar synthetic aperture radar revealed sinuous channels in the southwest of xanadu these channels feature very large radar cross sections up to 5 db whereas the angle of incidence was relatively high 20 this backscatter is larger than allowed by the coherent backscatter model considered to explain the unusual reflective and polarization properties of the icy satellites and only a few radar scattering mechanisms can be responsible for such high radar returns the presence of rounded icy pebbles with size larger than the radar wavelength 2 18 cm is proposed to explain the large radar cross sections measured in these units the radar bright channels are thus interpreted as riverbeds where debris likely shaped and transported by fluvial activity have been deposited similar debris were observed in the landing site of the huygens probe this work may point the way to an explanation for the enhanced brightness of other fluvial regions of titan

geomorphological significance of ontario lacus on titan integrated interpretation of cassini vims iss and radar data and comparison with the etosha pan namibia abstract ontario lacus is the largest lake of the whole southern hemisphere of titan saturn s major moon it has been imaged twice by each of the cassini imaging systems imaging science subsystem iss in 2004 and 2005 visual and infrared mapping spectrometer vims in 2007 and 2009 and radar in 2009 and 2010 we compile a geomorphological map and derive a hydrogeological interpretation of ontario lacus based on a joint analysis of iss vims and radar sar datasets along with the t49 altimetric profile acquired in december 2008 the morphologies observed on ontario lacus are compared to landforms of a semi arid terrestrial analog which resembles titan s lakes the etosha pan located in the owambo basin namibia the etosha pan is a flat floored depression formed by dissolution under semi arid conditions of a surface evaporitic layer calcretes controlled by groundwater vertical motions we infer that ontario lacus is an extremely flat and shallow depression lying in an alluvial plain surrounded by small mountain ranges under climatic conditions similar to those of terrestrial semi arid regions channels are seen in the southern part of ontario lacus in vims and radar data acquired at a 2 years time interval their constancy in location with time implies that the southern portion of the depression is probably not fully covered by a liquid layer at the time of the observations and that they most probably run on the floor of the depression a shallow layer of surface liquids corresponding to the darkest portions of the radar images would thus cover about 53 of the surface area of the depression of which almost 70 is located in its northern part these liquid covered parts of the depression where liquid ethane was previously identified are interpreted as topographic lows where the alkanofer raises above the depression floor the rest of the depression and mostly its southern part is interpreted as a flat and smooth exposed floor likely composed of a thick and liquid saturated coating of photon absorbing materials in the infrared this hypothesis could explain its dark appearance both in the infrared and radar data and the persistence of channels seen on the depression floor over the time shorelines are observed on the border of ontario lacus suggesting past high stand levels of the alkanofer table the analogy with the etosha pan suggests that ontario lacus depression developed at the expense of a soluble layer covering the region dissolution of this layer would be controlled by vertical motions of the alkanofer table over the time during flooding events liquid hydrocarbons covering the depression floor would dissolve the surface layer increasing progressively the diameter of the depression on geological timescales during drought episodes liquid hydrocarbons of the underground alkanofer would evaporate leading to crystallization of evaporites in the pores and at the surface of the substratum and to the formation of the regional soluble layer the presence of specific landforms lunette dunes or evaporites is compatible with such evaporitic regional settings alternatively but not exclusively the surface soluble layer might have formed by accumulation on the ground of soluble compounds formed in the atmosphere

thermal infrared emission spectroscopy of the pyroxene mineral series the thermal infrared emissivity spectra of coarse particulate samples of compositions in the pyroxene series display reststrahlen features absorptions that distinguish not only orthorhombic from monoclinic structures but also major end members within the two structural groups as well as minerals within solid solution series the exact number of reststrahlen features observed and their positions are dependent on mineral structure and cation occupancy of the m1 and m2 sites end member quadrilateral pyroxenes mg2si2o6 fe2si2o6 ca mg fe si2o6 are easily distinguished from each other and from minerals in the nonquadrilateral series nafesi2o6 na al fe si2o6 lialsi2o6 furthermore among quadrilateral pyroxenes variations in mg mg fe are linearly correlated with several band locations as are variations in ca content in high ca clinopyroxenes in both quadrilateral and nonquadrilateral compositions christiansen feature positions are also diagnostic no correlations with minor constituents of the order of 0 05 atoms per formula unit were observed the detailed spectral characteristics of pyroxenes and their variability as a function of structure and cation occupancy are presented here with determinative curves for the identification of pyroxene composition these data have important implications for the interpretation of spectral data from both laboratory and remote sensing instruments because they should permit a more detailed determination of pyroxene composition in measured unknown pure mineral and bulk compositions dominated by surface scattering i e all particulates greater than 65 m and solid samples

resonant wind driven mixing in the ocean boundary layer abstract the role of resonant wind forcing in the ocean boundary layer was examined using an ocean large eddy simulation les model the model simulates turbulent flow in a box measuring 100 300 m on a side whose top coincides with the ocean surface horizontal boundary conditions are periodic and time dependent wind forcing is applied at the surface two wind forcing scenarios were studied one with resonant winds that is winds that rotated at exactly the inertial frequency at 45 n and a second with off resonance winds from a constant direction the evolution of momentum and temperature for both cases showed that resonant wind forcing produces much stronger surface currents and vertical mixing in comparison to the off resonance case surface wave effects were also examined and found to be of secondary importance relative to the wind forcing the main goal was to quantify the main processes via which kinetic energy input by the wind is converted to potential energy in the form of changes in the

labyrinth terrain on titan abstract the cassini huygens mission revealed a terrain type on saturn s moon titan of dissected elevated plateaux with a high density of valleys named labyrinth terrain we define four subtypes of labyrinth terrains valleyed polygonal finely dissected and the possible outlier kronin labyrinth we mapped the locations of all labyrinths imaged by cassini and found they are distributed preferentially at high latitudes we characterize the labyrinths by morphometric parameters such as intervalley width valley width and percent valleys we find many labyrinths contain closed valleys which constrains their formation and evolution we also examine their low microwave emissivity spectral characteristics and find that the labyrinths are consistent with a bulk composition of dominantly organic materials with some component of water ice characteristics similar to titan s undifferentiated plains our analyses show that labyrinths are ancient terrains only the mountains and hummocky terrains are older this implies that significant organic production occurred early in titan s history the organic inventory represented by the labyrinths is estimated to be 15 42 of the solid organic inventory of titan or 14 35 of the total surface organics if the hydrocarbons of the lakes and seas are also included our preferred formation of the labyrinth terrains is erosion through dissolution and fluvial processes that dissect the plateaux in a manner similar to dissolution geology karst on earth this scenario requires that the organics that make up the labyrinth terrain be soluble in methane and or ethane liquids it also suggests that the origin of the plateaux may have derived from titan s past chemical production and subsequent depositional record

thermal infrared emissivity measurements under a simulated lunar environment application to the diviner lunar radiometer experiment 1 we present new laboratory thermal infrared emissivity spectra of the major silicate minerals identified on the moon measured under lunar environmental conditions and evaluate their application to lunar remote sensing data sets thermal infrared spectral changes between ambient and lunar environmental conditions are characterized for the first time over the 400 1700 cm 1 6 25 m spectral range for a fine particulate mineral suite including plagioclase albite and anorthite pyroxene enstatite and augite and olivine forsterite the lunar environment introduces observable effects in thermal infrared emissivity spectra of fine particulate minerals which include 1 a shift in the christiansen feature cf position to higher wave numbers shorter wavelengths 2 an increase in the overall spectral contrast and 3 decreases in the spectral contrast of the reststrahlen bands and transparency features our new measurements demonstrate the high sensitivity of thermal infrared emissivity spectra to environmental conditions under which they are measured and provide important constraints for interpreting new thermal infrared data sets of the moon including the diviner lunar radiometer experiment onboard nasa s lunar reconnaissance orbiter full resolution laboratory mineral spectra convolved to diviner s three spectral channels show that spectral shape cf position and band ratios can be used to distinguish between individual mineral groups and lunar lithologies the integration of the thermal infrared cf position with near infrared spectral parameters allows for robust mineralogical identifications and provides a framework for future integrations of data sets across two different wavelength regimes

investigating the shock histories of lunar meteorites miller range 090034 090070 and 090075 using petrography geochemistry and micro ftir spectroscopy fourier transform infrared ftir spectroscopy and cathodoluminescence cl imaging techniques combined with electron microprobe analyses have been used to determine the physical state of feldspathic phases that have been subject to varying levels of shock in the grouped lunar meteorites miller range 090034 090070 and 090075 six feldspathic phases have been identified based on spectral textural and chemical properties a specific infrared wavelength band ratio 1064 932 cm 1 equivalent to 9 40 10 73 m chosen because it can distinguish between some of the feldspathic phases can be used to estimate the pressure regimes experienced by these phases in addition ftir spatial mapping capabilities allow for visual comparison of variably shocked phases within the samples by comparing spectral and compositional data the origin and shock history of this lunar meteorite group has been determined with each of the shocked feldspathic phases being related to events in its geological evolution as such we highlight that ftir spectroscopy can be easily employed to identify shocked feldspathic phases in lunar samples estimate peak shock pressures and when compared with chemical data can be used to investigate their shock histories

surface mineralogy of martian low albedo regions from mgs tes data implications for upper crustal evolution and surface alteration 1 mars global surveyor thermal emission spectrometer mgs tes data are used to derive the modal mineralogy of spectrally distinct martian low albedo regions and to identify spatial trends in mineralogic assemblages results from this work are consistent with the major results of previous spectroscopic studies 1 plagioclase and clinopyroxene are the dominant minerals of most southern highlands regions 2 the northern plains exhibit the lowest pyroxene abundance within martian low albedo regions and 3 the highest concentrations of high silica phase s are found in the northern plains solis planum and a few southern high latitude regions low albedo regions may be classified into four units on the basis of relative abundances of plagioclase pyroxene and high silica phase s unit distributions between 45 latitude exhibit moderate correlation with distinct provinces e g syrtis major aonium sinus defined by large scale morphology elevation and to some extent surface age suggesting that the spectral and compositional differences between these units are more strongly controlled by original bedrock mineralogy than by surface atmosphere interactions and alteration syrtis major exhibits a difference in mineralogy from the surrounding highlands suggesting a differing degree of fractional crystallization assimilation or source region composition areas with thick crust near the tharsis plateau exhibit lower abundances of olivine and greater plagioclase pyroxene ratios than surrounding highland terrains suggesting that magmas in this region may have undergone increased olivine fractionation regions where surface alteration is more likely to be the primary control on observed spectral signatures are the high latitude areas 45 where globally surfaces dominated by high silica phase s are most commonly found

is titan s shape caused by its meteorology and carbon cycle 1 titan s shape is characterized by a difference between the long equatorial radius and the polar radius that is several hundred meters larger than that predicted by the flattening due to its spin rate the north polar region is covered by large mare filled with hydrocarbons including ethane moreover global circulation models predict ethane precipitation on the polar areas this study shows that the shape of titan can be explained by the subsidence associated with the substitution of methane with ethane rich liquids percolating into the crust which as suggested by evolution models may be composed of methane clathrate hydrates such substitutions have been observed in laboratory experiments this process would provide an additional methane source as required for sustaining the presence of this constituent in titan s atmosphere through its history a 270 m subsidence of the polar caps is explained by the circulation of 1 5 to 6 1018kg of ethane in the top three kilometers of an initially methane clathrate crust this process would have operated during the last 300 1200 myr at the present ethane production rate

quantifying upper ocean turbulence driven by surface waves 1 nearly all operational ocean models use air sea fluxes and the ocean shear and stratification to estimate upper ocean boundary layer mixing rates this approach implicitly parameterizes surface wave effects in terms of these inputs here we test this assumption using parallel experiments in a lake with small waves and in the open ocean with much bigger waves under the same wind stress and adjusting for buoyancy flux we find the mixed layer average turbulent vertical kinetic energy in the open ocean typically twice that in the lake the increase is consistent with models of langmuir turbulence in which the wave stokes drift and not wave breaking is the dominant mechanism by which waves energize turbulence in the mixed layer applying these same theories globally we find enhanced mixing and deeper mixed layers resulting from the inclusion of langmuir turbulence in the boundary layer parameterization especially in the southern ocean

bathymetry and absorptivity of titan s ontario lacus ontario lacus is the largest and best characterized lake in titan s south polar region in june and july 2009 the cassini radar acquired its first synthetic aperture radar sar images of the area together with closest approach altimetry acquired in december 2008 these observations provide a unique opportunity to study the lake s nearshore bathymetry and complex refractive properties average radar backscatter is observed to decrease exponentially with distance from the local shoreline this behavior is consistent with attenuation through a deepening layer of liquid and if local topography is known can be used to derive absorptive dielectric properties accordingly we estimate nearshore topography from a radar altimetry profile that intersects the shoreline on the east and west sides of the lake we then analyze sar backscatter in these regions to determine the imaginary component of the liquid s complex index of refraction the derived value 6 1 1 3 1 7 10 4 corresponds to a loss tangent of tan 9 2 2 0 2 5 10 4 and is consistent with a composition dominated by liquid hydrocarbons this value can be used to test compositional models once the microwave optical properties of candidate materials have been measured in areas that do not intersect altimetry profiles relative slopes can be calculated assuming the index of refraction is constant throughout the liquid accordingly we construct a coarse bathymetry map for the nearshore region by measuring bathymetric slopes for eleven additional areas around the lake these slopes vary by a factor of 5 and correlate well with observed shoreline morphologies

metal silicate mixtures spectral properties and applications to asteroid taxonomy the reflectance spectra of combinations of olivine orthopyroxene and iron meteorite metal show systematic variations in spectral properties which can be used to constrain many of the physical and chemical properties of the assemblages the presence of metal most noticeably affects band area ratios peak peak and peak minimum reflectance ratios and band widths these parameters are also affected to varying degrees by the abundance and grain size of the metal and silicates and the composition of the silicates band width and band areas are useful for determining metal abundance in olivine metal and orthopyroxene metal assemblages respectively mafic silicate grain size variations are best determined using band depth criteria band centers are most useful for determining mafic silicate composition analysis of the reflectance spectrum of the s class asteroid 8 flora on the basis of these spectral parameters indicates a surface composed of approximately 50 wt metal 40 wt olivine fa 35 10 10 wt orthopyroxene fs 30 25 35 and perhaps a few weight percent of clinopyroxene a substantial amount of the surface seems to consist of a fine grained 45 m size component analysis of the reflectance spectrum of the a class asteroid 446 aeternitas suggests a surface assemblage of approximately 35 wt metal 55 wt olivine fa 20 10 7 wt clinopyroxene fs 17 and 3 wt orthopyroxene fs 45 a substantial fine grained 45 m size surface component is also indicated for this asteroid

a model for formation of dust soil and rock coatings on mars physical and chemical processes on the martian surface 1 a model is presented here to explain the generation of surface material on mars using chemical magnetic and spectroscopic data from mars and geologic analogs from terrestrial sites one basic premise is that the dust soil units are not derived exclusively from local rocks but are rather a product of global and possibly remote weathering processes another assumption in this model is that there are both physical and chemical interactions of the atmosphere with dust particles and that these two processes create distinctly different products physical processes distribute dust particles on rocks and drift units forming physically aggregated layers these are reversible processes chemical reactions of the dust soil particles create alteration rinds on rock surfaces and cohesive crusted surface units between rocks both of which are relatively permanent materials according to this model the dominant components of the dust soil particles are derived from alteration of volcanic ash and tephra and contain primarily nanophase and poorly crystalline ferric oxide oxyhydroxide phases as well as silicates these phases are the alteration products that formed in a low moisture environment these dust soil particles also contain a smaller amount of material that was exposed to more water and contains crystalline ferric oxides oxyhydroxides sulfates and clay silicates these components could have formed through hydrothermal alteration at steam vents or fumeroles thermal fluids or through evaporite deposits wet dry cycling experiments are presented here on mars soil analogue mixtures containing poorly crystalline and crystalline components dominated by nanophase to 2 m diameter particles cemented products of these soil mixtures are formed in these experiments and variation in the surface texture was observed for samples containing smectites nonhydrated silicates or sulfates reflectance spectra were measured of the initial particulate mixtures the cemented products and ground versions of the cemented material the spectral contrast in the visible near infrared and midinfrared regions is significantly reduced for the cemented material compared to the initial soil and somewhat reduced for the ground cemented soil compared to the initial soil the results of this study suggest that transient fluvial activity on mars will have a profound effect on the texture and spectral properties of the dust soil particles on the surface the model developed in this study provides an explanation for the generation of cemented or crusted soil units and rock coatings on mars and may explain albedo variations on the surface observed near large rocks or crater rims

the influence of crosswind tidal currents on langmuir circulation in a shallow ocean 1 langmuir circulation lc is a turbulent process driven by wind and surface waves that plays a key role in transferring momentum heat and mass in the oceanic surface layer on the coastal shelves the largest scale lc span the whole water column and thus couple the surface and bottom boundary layers and enhance turbulent mixing observations and large eddy simulations les of a shallow coastal ocean demonstrate that these relatively large scale langmuir cells are strongly influenced by crosswind tidal currents two mechanisms by which crosswind tidal shear may distort and disrupt langmuir cells are proposed the first mechanism involves cell shearing due to differential advection across the whole cell for the second mechanism middepth vertical lc currents advect sheared mean crosswind current leading to the attraction of upwelling and downwelling regions so that lc cells are unsustainable when both regions overlap scaling arguments indicate that lc cells are more susceptible to crosswind shear distortion for smaller lc surface velocity convergence and greater cell aspect ratio vertical to horizontal lc scale which is consistent with the results obtained from the observations and les these results imply that scaling of lc characteristics in a coastal ocean differs from that in the open ocean which has important practical implications for parameterizing enhanced mixing due to lc

the latitudinal distribution of clouds on titan clouds have been observed recently on titan through the thick haze using near infrared spectroscopy and images near the south pole and in temperate regions near 40 s recent telescope and cassini orbiter observations are now providing an insight into cloud climatology to study clouds we have developed a general circulation model of titan that includes cloud microphysics we identify and explain the formation of several types of ethane and methane clouds including south polar clouds and sporadic clouds in temperate regions and especially at 40 in the summer hemisphere the locations frequencies and composition of these cloud types are essentially explained by the large scale circulation

three basaltic earth approaching asteroids and the source of the basaltic meteorites we report five color photometry near infrared spectra 0 8 2 5 m and thermal observations of the earth approaching asteroids 3551 1983 rd 3908 1980 pa and 4055 1985 do2 we derive their diameters as 1 2 1 0 and 3 4 km respectively apart from greater absorption band depths the spectra of these three small asteroids are nearly identical to that of vesta which is known to have a differentiated basaltic surface the deeper pyroxene bands 0 9 and 1 9 m relative to vesta are consistent with more pyroxene rich surfaces larger mineral grain sizes in their optically immature regoliths more bare rock surfaces or all of these factors these small earth approaching asteroids have similar orbits with perihelia near earth s orbit in july august they are probably not fragments of vesta but may be fragments of one or more vesta like parent bodies the spectra of vesta and the three earth approachers resemble those of the basaltic meteorites i e eucrites howardites and diogenites hed meteorites we find that hed fall times show a weak peak in july august suggesting that 3551 3908 and 4055 may be fragments of the source bodies of the hed meteorites or perhaps of a single common hed parent body the kilometer size asteroids have regoliths with significant insulating properties but these regoliths differ from that of the moon in that the particle sizes are larger than on the moon and lunar like glasses and agglutinates are largely absent the causes of these differences are related to impact velocities impact shaking and debris retention on small bodies differentiated basalt or mantle like asteroids may have impacted earth and left discontinuities in the geologic climatic record without leaving the chemical signatures associated with the k t boundary event

evidence of titan s climate history from evaporite distribution abstract water ice poor 5 m bright material on saturn s moon titan has previously been geomorphologically identified as evaporitic here we present a global distribution of the occurrences of the 5 m bright spectral unit identified with cassini s visual infrared mapping spectrometer vims and examined with radar when possible we explore the possibility that each of these occurrences are evaporite deposits the 5 m bright material covers 1 of titan s surface and is not limited to the poles the only regions with extensive long lived surface liquid we find the greatest areal concentration to be in the equatorial basins tui regio and hotei regio our interpretations based on the correlation between 5 m bright material and lakebeds imply that there was enough liquid present at some time to create the observed 5 m bright material we address the climate implications surrounding a lack of evaporitic material at the south polar basins if the south pole basins were filled at some point in the past then where is the evaporite

dissolution on titan and on earth toward the age of titan s karstic landscapes titan s polar surface is dotted with hundreds of lacustrine depressions based on the hypothesis that they are karstic in origin we aim at determining the efficiency of surface dissolution as a landshaping process on titan in a comparative planetology perspective with the earth as reference our approach is based on the calculation of solutional denudation rates and allow inference of formation timescales for topographic depressions developed by chemical erosion on both planetary bodies the model depends on the solubility of solids in liquids the density of solids and liquids and the average annual net rainfall rates we compute and compare the denudation rates of pure solid organics in liquid hydrocarbons and of minerals in liquid water over titan and earth timescales we then investigate the denudation rates of a superficial organic layer in liquid methane over one titan year at this timescale such a layer on titan would behave like salts or carbonates on earth depending on its composition which means that dissolution processes would likely occur but would be 30 times slower on titan compared to the earth due to the seasonality of precipitation assuming an average depth of 100 m for titan s lacustrine depressions these could have developed in a few tens of millions of years at polar latitudes higher than 70 n and s and a few hundreds of million years at lower polar latitudes the ages determined are consistent with the youth of the surface 1 gyr and the repartition of dissolution related landforms on titan

experimental constraints on the composition and dynamics of titan s polar lakes titan s polar lakes are thought to be predominantly composed of liquid ethane and methane however little is known on the ratio of these hydrocarbons in the lakes and the stability and dynamics of these mixtures here we provide the first experimental constraints under titan surface conditions of liquid hydrocarbon mixture evaporation our results are relevant to titan s polar temperatures and pressures 92 k and 1 5 bar and cover a wide range of methane ethane compositions we show that evaporation is negligible for pure ethane but increases nearly linearly with increasing methane concentration early dissolution of n2 results in ternary mixtures evaporating which is modeled by a hybrid thermodynamic equilibrium approach combining perturbed chain statistical associating fluid theory with a diffusion and buoyancy driven mass flux model the approach follows the experimental evaporation rate measurements presented in this study and allows for the calculation of the corresponding liquid methane ethane nitrogen ratios such results along with cassini inferred lake evaporation rates can be used to estimate the composition of titan s polar liquids and may have implications on their origin our results suggest that ontario lacus is predominantly composed of ethane 50 80 mol indicating it may be a residual lake following extensive seasonal methane evaporation and or might be in contact with a subsurface liquid reservoir

near infrared spectral reflectance of mineral mixtures systematic combinations of pyroxenes olivine and iron oxides near infrared spectral reflectance data are presented for systematic variations in weight percent of two component mixtures of ferromagnesian and iron oxide minerals mixtures were chosen for application to the study of the dark materials on mars but the results are equally applicable to mafic and ultramafic assemblages elsewhere in the solar system olivine spectral features are greatly reduced in contrast by admixture of other phases but remain distinctive even for low olivine contents clinopyroxene and orthopyroxene mixtures show resolved pyroxene absorptions near 2 m the addition of limonite greatly modifies pyroxene and olivine reflectance but does not fully eliminate distinctive spectral characteristics using only spectral data in the 1 m region it is difficult to differentiate orthopyroxene and limonite goethite in a mixture additional spectral coverage or other evidence may be required for a unique interpretation all composite mineral absorptions observed in this study are either weaker than or intermediate in strength to the end member absorptions and have bandwidths greater than or equal to those for the end members in general spectral properties in an intimate mixture combine in a complex nonadditive manner with features demonstrating a regular but usually nonlinear variation as a function of end member phase proportions

mineralogy of martian atmospheric dust inferred from thermal infrared spectra of aerosols 1 we have utilized optical constants derived from thermal infrared spectra acquired by the mariner 9 infrared interferometer spectrometer m9 iris and mars global surveyor thermal emission spectrometer mgs tes during periods of relatively high dust low water ice opacity to generate synthetic transmission and emission spectra of the atmospheric dust using libraries of transmission and emission spectra of common rock forming minerals and their alteration products we applied a linear deconvolution algorithm to the spectra to model the dust mineralogy models of the m9 iris transmission data generally are of poor quality and the mineralogical results of these fits are unlikely to be valid fits to the tes transmission spectrum and tes and iris emission spectra are of better quality and suggest that the dust mineralogy is dominated by framework silicates feldspar and or zeolite with carbonate sulfate pyroxene and olivine identified near but below generalized detection limits evidence for phyllosilicates is not robust our results combined with those from in situ measurements and other visible to infrared spectral studies suggest that framework silicates probably feldspar dominate the dust mineralogy with lesser amounts of olivine pyroxene amorphous material hematite and magnetite and that the dust largely is the product of mechanical weathering of basaltic rocks with minor chemical alteration

cosmochemical and spectroscopic properties of northwest africa 7325 a consortium study this work is part of a project to build an infrared database in order to link ir data of planetary materials and therefore possible mercury material with remote sensing observations of mercury which will probably be obtained by the mertis instrument on the forthcoming bepicolombo mission the unique achondrite northwest africa nwa 7325 which has previously been suggested to represent the first sample from mercury was investigated by optical and electron microscopy and infrared and raman spectroscopy in addition the oxygen strontium xenon and argon isotopes were measured and the abundance of selected trace elements determined the meteorite is a cumulate rock with subchondritic abundances of hfse and ree and elevated sr contents which underwent a second heating and partial remelting process oxygen isotope measurements show that nwa 7325 plots in the ureilite field close to the alm a trachyandesitic fragment found in the unique almahata sitta meteorite breccia on the other hand mineralogical investigations of the pyroxenes in nwa 7325 provide evidence for similarities to the lodranites and acapulcoites furthermore the rock is weakly shocked and argon isotope data record ancient 4 5 ga plateau ages that have not been reset the sample records a cosmogenic exposure age of 19 ma systematics of rb sr indicate an extreme early volatile depletion of the precursor material similar to many other achondrite groups however despite its compositional similarities to other meteorite groups our results suggest that this meteorite is unique and unrelated to any other known achondrite group an origin for nwa 7325 as a sample from the planet mercury is not supported by the results of our investigation in particular the evidence from infrared spectroscopy indicates that a direct relationship between nwa 7325 and the planet mercury can be ruled out no acceptable spectral match between laboratory analyses and remote sensing observations from mercury has been obtained however we demonstrate that infrared spectroscopy is a rapid and nondestructive method to characterize mineral phases and thus an excellent tool for planetary surface characterization in space missions

mineralogical composition of sands in meridiani planum determined from mars exploration rover data and comparison to orbital measurements constraints on the mineralogical composition of low albedo low sulfur sands at meridiani planum are determined from mars exploration rover mer opportunity miniature thermal emission spectrometer mini tes mossbauer and alpha proton x ray spectrometer measurements results of this work show that the sand is olivine basaltic in composition with minor amounts of sulfate and a high silica phase glass or secondary amorphous silica measurements from all three instruments indicate that pyroxene is twice as abundant as olivine and that the pyroxene composition is dominated by the low calcium variety the volume abundance of olivine is constrained to be 10 15 results from detailed analyses of mer data are used to ground truth the spectral emissivity and mineral abundances derived from orbit with mars global surveyor tes data tes derived mineral abundances are within 5 of those derived from mer data which is generally within the statistical errors associated with tes derived phase abundances the agreement lends support to global and regional scale variations in mineralogical composition determined from tes data in previous studies an alternative method of least squares minimization is used for modeling the tes and mini tes data the benefits of this method are demonstrated by comparison with conventional least squares techniques previously used by tes data users

global spectral classification of martian low albedo regions with mars global surveyor thermal emission spectrometer mgs tes data 1 martian low albedo surfaces defined here as surfaces with mars global surveyor thermal emission spectrometer mgs tes albedo values 0 15 were reexamined for regional variations in spectral response low albedo regions exhibit spatially coherent variations in spectral character which in this work are grouped into 11 representative spectral shapes the use of these spectral shapes in modeling global surface emissivity results in refined distributions of previously determined global spectral unit types surface types 1 and 2 pure type 2 surfaces are less extensive than previously thought and are mostly confined to the northern lowlands regional scale spectral variations are present within areas previously mapped as surface type 1 or as a mixture of the two surface types suggesting variations in mineral abundance among basaltic units for example syrtis major which was the surface type 1 type locality is spectrally distinct from terrains that were also previously mapped as type 1 a spectral difference also exists between southern and northern acidalia planitia which may be due in part to a small amount of dust cover in southern acidalia groups of these spectral shapes can be averaged to produce spectra that are similar to surface types 1 and 2 indicating that the originally derived surface types are representative of the average of all low albedo regions

geologic characteristics of relatively high thermal inertia intracrater deposits in southwestern margaritifer terra mars 1 twenty one craters in southwestern margaritifer terra exhibit unusually warm interior deposits in nighttime thermal emission imaging system themis infrared images these deposits exhibit nighttime temperatures as high as 223 k and are 5 18 warmer than the surrounding plain thermal inertia values derived from thermal emission spectrometer tes data are greater for the deposits than the plains with maximum values between 455 and 675 j m 2 k 1 s 1 2 analysis of themis thermal inertia data having nearly an order of magnitude better spatial resolution shows that the deposits can have a thermal inertia as high as 1060 j m 2 k 1 s 1 2 albedo and dust cover index values suggest that both the deposits and the surrounding region are generally dust free compositional analysis with tes and themis data show that though a small number of the deposits may have isolated compositional differences the majority of the deposits have a composition similar to that of the surrounding plains the geomorphology of the craters as viewed from mars orbiter camera moc images shows that the deposits are coherent units rather than sand deposits an observation that is consistent with the relatively high thermal inertia values if these deposits are coherent rock units as the results of our study suggest possible methods of formation include emplacement of primary igneous material or lithification of sediments from surrounding terrain

large eddy simulations of upper ocean response to a midlatitude storm and comparison with observations abstract a large eddy simulation les model is used to investigate an upper ocean response to a fall storm in the open ocean of the north pacific ocean the storm is characterized by rapid increases in wind speed and surface heat loss but a relatively steady wave field the les model shows that surface convergence zones or windrows organize into line patterns aligned with the wind direction evolving from nearly parallel lines to irregular structures featuring y junctions as the wind speed increases the downwelling to upwelling velocity ratio ranges between 1 2 and 1 6 indicating a moderate level of asymmetry between the downwelling and upwelling plumes in langmuir circulation during the storm the turbulent langmuir number lat increases from 0 2 to 0 5 while the vertical turbulence intensity w2 decreases from 1 4 to 0 7 u 2 where u is the friction velocity the order of turbulence intensities in three directions switches from crosswind vertical downwind directions to downwind crosswind ver

the stubenberg meteorite an ll6 chondrite fragmental breccia recovered soon after precise prediction of the strewn field on march 6 2016 at 21 36 51 ut extended areas of upper austria bavaria germany and the southwestern part of the czech republic were illuminated by a very bright bolide this bolide was recorded by instruments in the czech part of the european fireball network and it enabled complex and precise description of this event including prediction of the impact area so far six meteorites totaling 1473 g have been found in the predicted area the first pieces were recovered on march 12 2016 on a field close to the village of stubenberg bavaria stubenberg is a weakly shocked s3 fragmental breccia consisting of abundant highly recrystallized rock fragments embedded in a clastic matrix the texture the large grain size of plagioclase and the homogeneous compositions of olivine fa31 4 and pyroxene fs25 4 clearly indicate that stubenberg is an ll6 chondrite breccia this is consistent with the data on o ti and cr isotopes stubenberg does not contain solar wind implanted noble gases data on the bulk chemistry ir spectroscopy cosmogenic nuclides and organic components also indicate similarities to other metamorphosed ll chondrites noble gas studies reveal that the meteorite has a cosmic ray exposure cre age of 36 3 ma and that most of the cosmogenic gases were produced in a meteoroid with a radius of at least 35 cm this is larger than the size of the meteoroid which entered the earth s atmosphere which is constrained to 20 cm from short lived radionuclide data in combination this might suggest a complex exposure history for stubenberg

shoreline features of titan s ontario lacus from cassini vims observations we analyze observations of titan s south polar lake ontario lacus obtained by cassini s visual and infrared mapping spectrometer during the 38th flyby of titan t38 2007 december 5 these near closest approach observations have the highest signal to noise the finest spatial resolution and the least atmospheric influence of any near infrared lake observation to date we use the large spatially flat and low albedo interior of ontario lacus as a calibration target allowing us to derive an analytical atmospheric correction for emission angle the dark lake interior is surrounded by two separate annuli that follow the lake interior s contours the inner annulus is uniformly dark but not so much as the interior lake and is generally 5 10 kilometers wide at the lake s southeastern margin we propose that it represents wet lakebed sediments exposed by either tidal sloshing of the lake or seasonal methane loss leading to lower lake volume the exterior annulus is bright and shows a spectrum consistent with a relatively low water ice content relative to the rest of titan it may represent fine grained condensate deposits from a past era of higher lake level together the annuli seem to indicate that the lake level for ontario lacus has changed over time this hypothesis can be tested with observations scheduled for future titan flybys

the bathymetry of a titan sea construct the depth profile the bathymetry of titan s large sea ligeia mare from cassini radar data collected during the 23 may 2013 t91 nadir looking altimetry flyby we find the greatest depth to be about 160 m and a seabed slope that is gentler toward the northern shore consistent with previously imaged shoreline morphologies low radio signal attenuation through the sea demonstrates that the liquid for which we determine a loss tangent of 3 1 10 5 is remarkably transparent requiring a nearly pure methane ethane composition and further that microwave absorbing hydrocarbons nitriles and suspended particles be limited to less than the order of 0 1 of the liquid volume presence of nitrogen in the ethane methane sea expected based on its solubility and dominance in the atmosphere is consistent with the low attenuation but that of substantial dissolved polar species or suspended scatterers is not

surface wave effects on high frequency currents over a shelf edge bank abstractseveral acoustic doppler current profilers and vertical strings of temperature conductivity and pressure sensors deployed on and around the east flower garden bank efgb were used to examine surface wave effects on high frequency flows over the bank and to quantify spatial and temporal characteristic of these high frequency flows the efgb about 5 km wide and 10 km long is located about 180 km southeast of galveston texas and consists of steep slopes on southern and eastern sides that rise from water depths over 100 m to within 20 m of the surface three dimensional flows with frequencies ranging from 0 2 to 2 cycles per hour cph were observed in the mixed layer when wind speed and stokes drift at the surface were large these motions were stronger over the bank than outside the perimeter the squared vertical velocity w2 was strongest near the surface and decayed exponentially with depth and the e folding length of w2 was 2 times larger than that of stokes drift the 2 h averaged w2 i

distribution and characteristics of adirondack class basalt as observed by mini tes in gusev crater mars and its possible volcanic source abstract we identified 104 unique rock targets belonging to the olivine rich adirondack class using mini tes data rare rocks on the west spur of the columbia hills and on the plains east of the hills also belong to this class we present evidence that adirondack class basaltic lavas may have had their origin at apollinaris tholus linear modeling of adirondack class rock spectra shows only minor variations in mineralogy and the primary phases identified are consistent with olivine basalt having an average olivine composition of fo 45 we used factor analysis and target transformation to identify variability within a single class of rocks for the first time and we find that olivine abundance varies independently of a basaltic matrix a spectral component previously attributed to downwelling radiance is proposed here to be attributable to optically thin dust on rocks which has a greater effect on mini tes spectra than previously recognized but can explain the sloping continuum observed in adirondack class rock spectra as well as the apparent distortion of an olivine absorption spectral mixing is not completely linear leading to the overestimation of sulfate and olivine fractions and the underestimation of plagioclase feldspar although linear mixing appears to successfully replicate the majority of the observed signal published tes spectra of low albedo low dust cover olivine bearing materials do not exhibit the spectral telltales of non linear behavior probably because orbital spectra represent mostly mobile regolith that has not accumulated a sufficient dust cover over 3 6 km areas

three dimensional flow in the upper ocean measurements made from the research platform flip provide some of the first direct observations of three dimensional flow within the surface mixed layer of the ocean relatively narrow regions of downwelling flow were found within the mixed layer in coincidence with bands of convergent surface flow at mid depth in the mixed layer the downwelling flow had magnitudes of up to 0 2 meter per second and was accompanied by a downwind horizontal jet of comparable magnitude there is some evidence that these motions transport heat and phytoplankton within the mixed layer

velocity structure in the mixed layer during mildex abstract during october november 1983 a mixed layer dynamics experiment mildex took place off the coast of california as a part of mildex a number of sensors were deployed from the research platform flip in an effort to monitor the flow structure in the near surface mixed layer profiling current meters vmcms measured velocities down to 150 m on an hourly basis other vmvms were set at fixed depths depths of interest were examined using a package which measured three component velocities and displayed them in flip s laboratory in real time the current meters often observed sequences of downwind directed jets with maximum velocities exceeding 25 cm s 1 downwelling velocities of equal magnitude were also observed the strongest currents were found 10 to 35 m below the surface at mid depth in the mixed layer surface convergences associated with these jets were visualized by scattering tracers computer cards on the sea surface these features suggest langmuir circulation six doppler sonars wer

effects of wave rollers and bottom stress on wave setup 1 setup the increase in the mean water level associated with breaking waves observed between the shoreline and about 6 m water depth on an ocean beach is predicted well by a model that includes the effects of wave rollers and the bottom stress owing to the mean flow over the 90 day observational period the measured and modeled setups are correlated squared correlation above 0 59 and agree within about 30 although rollers may affect setup significantly on beaches with large amplitude several meters high sandbars and may be important in predicting the details of the cross shore profile of setup for the data discussed here rollers have only a small effect on the amount of setup conversely bottom stress calculated using eddy viscosity and undertow formulations based on the surface dissipation and assuming that the eddy viscosity is uniform throughout the water column significantly affects setup predictions neglecting bottom stress results in underprediction of the observed setup in all water depths with maximum underprediction near the shoreline where the observed setup is largest

determination of the elemental composition of rocks on venus by venera 13 and venera 14 preliminary results venera 13 and venera 14 have determined for the first time ever the elemental composition of the venusian rocks at the probes landing sites to study venusian rocks rolling upland and flat lowland have been chosen as the most typical of the entire planetary surface venera 13 landed on the rolling upland while venera 14 landed in the region with lower topography the chemical composition of the rock at the venera 13 landing site proved to be similar to the composition of potassium alkaline basalts of the earth s crust rocks which can be found on oceanic islands and in rift zones the chemical composition of the rock at the venera 14 landing site is similar to that of tholeiitic basalts of the oceanic crust of the earth the comparison of new data on the composition of venusian rocks with the composition of the rocks of similar provinces on the earth and the moon shows that the evolution of the surface and crust of venus was not similar to that of the earth and especially not that of the moon

pyroxene spectroscopy revisited spectral compositional correlations and relationship to geothermometry the authors wish to thank the various agencies which have provided the necessary support for this project including grants in aid of research from sigma xi the scientific research society to e a c the geological society of america grant 3741 87 to e a c and nasa planetary geology and geophysics grant nagw 642 to m j g

near and mid infrared microspectroscopy of the ronda peridotite 1 microspectroscopy is a potentially useful tool for planetary applications as individual mineral grains can be targeted and measured in situ a series of closely coupled experiments was designed to investigate and compare the laboratory measurement of optical properties of a peridotite sample in the macroscale and microscale the ronda peridotite consists largely of olivine with significant orthopyroxene and minor clinoproxene and serpentine microscopic transmission spectra of unmounted thin sections produce strong well defined absorption features in the near infrared and band positions can be directly compared to macroscopic and microscopic reflectance spectra for near infrared reflectance where photons are multiply scattered by different grains measurement of a microscopic target means most photons are scattered out of the field of view and few photons return to the detector from the target area this precludes most microspectroscopic reflectance measurements of small features in the near infrared in the mid infrared where reflectance measurements involve only surface interactions microspectroscopic measurements detect well defined absorption features for most samples although the intensity of absorption features varies between grains band positions are consistent with macroscopic diffuse reflectance and emittance measurements of bulk samples and can be used to extract general chemical information such as iron magnesium ratios of olivines

bulk mineralogy of the ne syrtis and jezero crater regions of mars derived through thermal infrared spectral analyses abstract we investigated the area to the northwest of the isidis impact basin hereby referred to as nw isidis using thermal infrared emission datasets to characterize and quantify bulk surface mineralogy throughout this region this area is home to jezero crater and the watershed associated with its two deltaic deposits in addition to ne syrtis and the strong and diverse visible near infrared spectral signatures observed in well exposed stratigraphic sections the spectral signatures throughout this region show a diversity of primary and secondary surface mineralogies including olivine pyroxene smectite clays sulfates and carbonates while previous thermal infrared investigations have sought to characterize individual mineral groups within this region none have systematically assessed bulk surface mineralogy and related these observations to visible near infrared studies we utilize an iterative spectral unmixing method to statistically evaluate our linear thermal infrared spectral unmixing models to derive surface mineralogy all relevant primary and secondary phases identified in visible near infrared studies are included in the unmixing models and their modeled spectral contributions are discussed in detail while the stratigraphy and compositional diversity observed in visible near infrared spectra are much better exposed and more diverse than most other regions of mars our thermal infrared analyses suggest the dominance of basaltic compositions with less observed variability in the amount and diversity of alteration phases these results help to constrain the mineralogical context of these previously reported visible near infrared spectral identifications the results are also discussed in the context of future in situ investigations as the nw isidis region has long been promoted as a region of paleoenvironmental interest on mars

dust coatings on basaltic rocks and implications for thermal infrared spectroscopy of mars 1 thin coatings of atmospherically deposited dust can mask the spectral characteristics of underlying surfaces on mars from the visible to thermal infrared wavelengths making identification of substrate and coating mineralogy difficult from lander and orbiter spectrometer data to study the spectral effects of dust coatings we acquired thermal emission and hemispherical reflectance spectra 5 25 m 2000 400 cm 1 of basaltic andesite coated with different thicknesses of air fall deposited palagonitic soils fine grained ceramic clay powders and terrestrial loess the results show that thin coatings 10 20 m reduce the spectral contrast of the rock substrate substantially consistent with previous work this contrast reduction continues linearly with increasing coating thickness until a saturation thickness is reached after which little further change is observed the saturation thickness of the spectrally flat palagonite coatings is 100 120 m whereas that for coatings with higher spectral contrast is only 50 75 m spectral differences among coated and uncoated samples correlate with measured coating thicknesses in a quadratic manner whereas correlations with estimated surface area coverage are better fit by linear functions linear mixture modeling of coated samples using the rock substrate and coating materials as end members is also consistent with their measured coating thicknesses and areal coverage a comparison of ratios of thermal emission spectrometer tes spectra of dark and bright intracrater and windstreak deposits associated with radau crater suggests that the dark windstreak material may be coated with as much as 90 areal coverage of palagonitic dust the data presented here also will help improve interpretations of upcoming mini tes and thermal emission imaging system themis observations of coated mars surface materials

thermal infrared spectroscopy of experimentally shocked anorthosite and pyroxenite implications for remote sensing of mars 1 the feldspar and pyroxene mineralogies on mars revealed by the thermal emission spectrometer tes on mars global surveyor likely record a variety of shock effects as suggested by petrologic analyses of the martian meteorites and the abundance of impact craters on the planet s surface to study the effects of shock pressures on thermal infrared spectra of these minerals we performed shock recovery experiments on orthopyroxenite and anorthosite samples from the stillwater complex montana over peak pressures from 17 to 63 gpa we acquired emissivity and hemispherical reflectance spectra 350 1400 cm 1 7 29 mm of both coherent chips and fine grained powders of shocked and unshocked samples these spectra are more directly comparable to remotely sensed data of mars e g tes than previously acquired absorption or transmission spectra of shocked minerals the spectra of experimentally shocked feldspar show systematic changes with increasing pressure due to depolymerization of the silica tetrahedra for the spectra of chips this includes the disappearance of small bands in the 500 650 cm 1 region and a strong band at 1115 cm 1 and changes in positions of a strong band near 940 cm 1 and the christiansen feature near 1250 cm 1 spectra of the shocked powders show the gradual disappearance of a transparency feature near 830 cm 1 fewer changes are observed in the pyroxene spectra at pressures as high as 63 gpa spectra of experimentally shocked minerals will help identify more precisely the mineralogy of rocks and soils not only from tes but also from future mars instruments such as minites and themis index terms 3944 mineral physics shock wave experiments 3934 mineral physics optical infrared and raman spectroscopy 5420 planetology solid surface planets impact phenomena includes cratering 5460 planetology solid surface planets physical properties of materials keywords anorthosite pyroxenite shock spectra thermal infrared remote sensing mars

hydrocarbon lakes on titan distribution and interaction with a porous regolith from 10 to more than 100 000 km 2 the size and location of lakes provide constraints on parameters associated with subsurface transport using porous media properties inferred from huygens probe observations timescales for flow into and out of observed lakes are shown to be in the tens of years similar to seasonal cycles derived timescales are compared to the time between collocated sar observations in order to considertheroleofsubsurfacetransportintitan shydrologic cycle citation hayes a et al 2008 hydrocarbon lakes on titan distribution and interaction with a porous regolith geophys res lett 35 l09204 doi 10 1029 2008gl033409

geomorphologic mapping of titan s polar terrains constraining surface processes and landscape evolution abstract we present a geomorphologic map of titan s polar terrains the map was generated from a combination of cassini synthetic aperture radar sar and imaging science subsystem imaging products as well as altimetry sartopo and radargrammetry topographic datasets in combining imagery with topographic data our geomorphologic map reveals a stratigraphic sequence from which we infer process interactions between units in mapping both polar regions with the same geomorphologic units we conclude that processes that formed the terrains of the north polar region also acted to form the landscape we observe at the south uniform sar dark plains are interpreted as sedimentary deposits and are bounded by moderately dissected uplands these plains contain the highest density of filled and empty lake depressions and canyons these units unconformably overlay a basement rock that outcrops as mountains and sar bright dissected terrains at various elevations across both poles all these units are then superposed by surficial units that slope towards the seas suggestive of subsequent overland transport of sediment from estimates of the depths of the embedded empty depressions and canyons that drain into the seas the sar dark plains must be 600 m thick in places though the thickness may vary across the poles at the lowest elevations of each polar region there are large seas which are currently liquid methane ethane filled at the north and empty at the south the large plains deposits and the surrounding hillslopes may represent remnant landforms that are a result of previously vast polar oceans where larger liquid bodies may have allowed for a sustained accumulation of soluble and insoluble sediments potentially forming layered sedimentary deposits coupled with vertical crustal movements the resulting layers would be of varying solubilities and erosional resistances allowing formation of the complex landscape that we observe today

langmuir circulations in a surface layer bounded by a strong thermocline abstract langmuir circulations reside in and are responsible in part for the existence and maintenance of the mixed layer it is therefore typical for the water containing langmuir circulations to be bounded below by a thermocline when this bounding thermocline is strong it may be expected to act as an effective slippery bottom constraint such an assumption has been invoked previously but failed to predict a preferred spacing for the windrows produced by the circulations this model assumed that the momentum transfers across the horizontal boundaries of the mixed layer were independent of the water motion induced by langmuir circulation here mixed boundary conditions are explored estimates of the transfer coefficients in these boundary conditions suggest that the revised model differs only slightly from the earlier one but allows for a more general and realistic stress model incorporating these effects into the theory gives windrows with a finite separation in accord with the observations

structure and variability of langmuir circulation during the surface waves processes program a cooperative multiplatform field experiment was conducted in the eastern north pacific during february and march of 1990 as part of the surface waves processes program swapp one of the experimental objectives was to investigate langmuir circulation so that its role in the evolution of the oceanic surface boundary layer could be better understood the concurrent use of different observational techniques ranging from simple surface drifters to complex doppler sonar systems resulted in new information about langmuir circulation structure and variability estimates of langmuir cell spacing indicated that a broad range of scales from about 2 to 200 m was excited during periods of strong surface forcing and that the energy containing scales evolved with time estimates of cell spacing based on doppler velocities from a surface scanning sonar directed crosswind showed this scale evolution but estimates based on backscattered intensity did not this was attributed to the fact that the intensity based estimates were only indirectly related to circulation strength the near surface convergent velocities from the sonar were used to form an objective quantitative measure of the temporal variations in langmuir circulation strength as expected the circulation strength increased dramatically during strong wind events however circulation strength and wind stress did not decrease simultaneously and langmuir circulation was detectable for up to a day after abrupt reductions in wind stress energy from the surface wave field which decayed more slowly than the wind was apparently responsible for maintaining the circulation the variation of circulation strength was found to be better related to u us than to u where u is the friction velocity is the wind stress and us is the surface wave stokes drift this scaling is consistent with wave current interaction theories of langmuir cell generation

electromagnetic models and inversion techniques for titan s ontario lacus depth estimation from cassini radar data abstract since 2004 cassini radar operating at 13 8 ghz as a radiometer scatterometer altimeter and synthetic aperture radar sar provides a vast amount of data suggesting new scenarios for titan s morphology and evolution an important result was the detection of lakes constituted by liquid hydrocarbons thus supporting the hypothesis of a methane and ethane cycle similar to water cycle on earth in 2007 ontario lacus a 200 km 70 km lake was detected near the south pole to date ontario is the only large liquid area sensed by cassini radar in the southern hemisphere of titan in this work we analyze the sar data using two different electromagnetic modeling approaches to retrieve the optical thickness parameter of the liquid hydrocarbon layer a physically based model iem combined with a gravity capillary wave spectra and integrated into a bayesian statistical inversion is compared with a semi empirical model also based on a double layer description we consider the impact of the dielectric constant of the surface constituents as well as wind speed and wave motion scenarios on the retrieved optical thickness and by extension the lake depth and volume estimation wind speed can be constrained below 0 7 m s in good agreement with the forecasts of global circulation models on titan lake depths estimates depend on the hypotheses on wind speed and loss tangent of the liquid the average depth lake estimates obtained with the physically based approach range from 2 7 and 8 3 m with the 95 of the lake area not exceeding 30 m depth the semiempirical model results confirm this interval also considering the hypothesis of a low reflectivity lake bed this would imply lower depth with a significant part of the lake area not liquid filled at the present

observed growth of langmuir circulation surface velocity patterns and upper ocean density profiles are presented from a period following a sudden increase in wind a prior wind speed of 8 m s failed to produce visible signs of langmuir circulation after the wind speed increased to 13 m s langmuir circulation developed within 15 min the initial scale observed was about 16 m streak to streak and may have been restricted by the depth scale of the measurements this spacing is about two thirds of the dominant wavelength 4 s period waves the streak spacing two cell widths increased at roughly 40 m h for the next hour the density measurements indicate a depth of mixing which increased over the same period at a rate of 20 m h thus the vertical to horizontal aspect ratio was about 1 1 prior stratification was weak buoyancy frequency of about 1 5 cph and probably did not affect the circulation initially mixing at the surface of the oceans is important to a wide variety of concerns including global climate and the health of marine life two main causes of this mixing can be identified 1 when surface water is cooled it becomes denser and sinks mixing downward either to the bottom or until limited by the preexisting stratification and 2 the wind can mechanically stir the surface layer to some depth usually limited by stratification the former can result in mixing to considerable depths but the latter occurs more often over the majority of the world oceans frequently the two driving forces occur together what are the details of this mixing for example are bubbles dragged deep into the mixed layer injecting gases at depth are there repeatable features which could lead to improved models of surface mixing and its effects when wind blows over water lines are often visible on the surface running roughly parallel to the wind in an exemplary series of experiments langmuir 1938 found these to be lines of convergence along the surface with downwelling below each line he found also that maxima in the downwind surface currents occur along these lines thus the mixing layer is organized into rolls of alternating sign aligned with the wind and water parcels follow helical paths downwind this form of circulation in surface layers of water has come to be called langmuir circulation historically this term has not implied any particular mechanism of formation and it generally has not been used in reference to other similar structures e g roll vortices in the atmosphere or in wall bounded convection langmuir 1938 p 123 expressed his belief that the helical vortices set up by wind apparently constitute the essential mechanism by which the epilimnion is produced clearly this form of helical vortices is efficient in transporting momentum energy and matter throughout the surface layer of water three mechanisms are currently considered to drive langmuir circulation 1 an interaction between surface waves and winddriven shear gives rise to this form of circulation as a linear instability a review of this theory and of observations before 1983 is given by leibovich 1983 2 even without surface waves turbulent mixing will occur due to the breakdown of the

evolution of langmuir circulation during a storm wind stress waves stratification velocity profiles and surface fields of radial velocity and acoustic backscatter intensity were measured along a drift track 50 to 150 km off point arguello california on march 8 1995 the wind increased from calm to 12 m s from the se opposing swell from the nw it increased to 15 m s at noon utc on march 9 remained steady over the next 12 hours briefly dropped and veered by 60 then returned a mixed layer deepened quickly to 25 m then held roughly steady through the next 2 days in spite of gusty winds continuing at 15 25 m s a phased array doppler sonar system took measurements covering 250 m by 150 m of the surface with 5 m by 10 m spatial resolution averages over 6 min removed surface waves permitting continuous assessment of strength orientation spacing and degree of organization of features associated with surface motion e g langmuir circulation even when conditions were too rough for visual assessment several results stand out 1 as found previously most wind mixing arises from inertial shear across the thermocline 2 consistent with wind wave forcing of langmuir circulation plueddemann et al 1996 suggest that surface velocity variance scales like u us where u is friction velocity and us is the surface stokes drift however the measurements here scale with us 1 alone once langmuir circulation is established 3 the velocity variance is weaker here than expected given the magnitudes of wind and waves leading to a smaller estimated mixing effect 4 large vacillations in lc strength are seen just before the brief veering of the wind it is suggested that bubble buoyancy could play a dynamic role 5 mean orientation and spacing can differ for intensity versus radial velocity features

organized structures in subsurface bubble clouds langmuir circulation in the open ocean observations of the movement and distribution of subsurface bubbles reveal the structure of coherent motions near the ocean surface the measurements were obtained in the open ocean from a freely drifting self contained acoustical instrument equipped with side scan sonar dual frequency echo sounders and ambient sound recording systems the bubble clouds are organized into long narrow plumes aligned with the wind consistent with windrows caused by langmuir circulations they have widths of about 3 to 5 m and lengths up to 100 m with multiple scales coexisting their mean separation depends upon wind speed below 5 m s 1 mean spacings were about 5 m increasing to 10 m when winds exceeded 10 m s 1 the maximum depth to which the plumes were observed to penetrate depended to some extent on wind speed with the greatest penetrations of 12 m occurring at the highest wind speeds 13 m s 1 however the time averaged depth of observed bubble plume penetration bears only a weak dependence on wind speed whenever winds exceeded 5 m s 1 a mean penetration depth of 6 m was observed associated with these bubble plumes were maximum downward velocities of about 0 06 m s 1 these speeds were detected at 8 m depth in the center of the plumes magnitudes decreased to zero near the surface and horizontally toward the boundaries of the plumes

seeking phyllosilicates in thermal infrared data a laboratory and martian data case study 1 previous analyses of thermal emission spectrometer tes data produce results that could suggest a widespread distribution of phyllosilicate minerals over the surface of mars whereas studies of visible to near infrared vnir data indicate a more limited distribution we use vnir detections of phyllosilicates in the vicinity of the nili fossae to determine the spectral characteristics of phyllosilicate bearing material in the thermal infrared tir by investigating areas of vnir phyllosilicate detection in more detail we find that the phyllosilicate bearing material corresponds to spectral variation in thermal emission imaging system decorrelation stretched tir images and differences in infrared spectral shape that are consistent with but not uniquely attributable to mixtures of phyllosilicates and basalt phyllosilicate phases are modeled from tes data at abundances that average 5 over the region and at abundances near the 10 15 detection limit in our specific regions of interest deconvolution of numerical mixtures of phyllosilicate and basalt spectra indicates that these low abundances of phyllosilicates likely are not influenced by uncertainties greater than the 10 15 uncertainty of the method tes spectra and modeled abundances vary between the phyllosilicate bearing material and the surrounding region but this difference in composition cannot be attributed solely to the presence of phyllosilicates we believe the inconsistencies in phyllosilicate occurrence between tes and vnir analyses may be explained by the inclusion of phyllosilicates in the models of tes data as substitutes for poorly crystalline phases e g allophane not currently available in public infrared spectral libraries

an asymmetric distribution of lakes on titan as a possible consequence of orbital forcing a set of lakes filled or partially filled with liquid hydrocarbon and empty lake basins have been discovered in the high latitudes of saturn s moon titan these features were mapped by the radar instrument on the cassini orbiter here we quantify the distribution of the lakes and basins and show a pronounced hemispheric asymmetry in their occurrence whereas significant fractions of the northern high latitudes are covered by filled and empty lakes the same latitudes in the southern hemisphere are largely devoid of such features we propose that in addition to known seasonal changes the observed difference in lake distribution may be caused by an asymmetry in the seasons on titan that results from the eccentricity of saturn s orbit around the sun we suggest that the consequent hemispheric difference in the balance between evaporation and precipitation could lead to an accumulation of lakes in one of titan s hemispheres this effect would be modulated by and reverse with dynamical variations in the orbit we propose that much like in the earth s glacial cycles the resulting vigorous hydrologic cycle has a period of tens of thousands of years and leads to active geologic surface modification in the polar latitudes

turbulent large eddy momentum flux divergence during high wind events abstractmomentum transport by energy containing turbulent eddies in the oceanic mixed layer were investigated during high wind events in the northern gulf of alaska off kayak island sixteen high wind events with magnitudes ranging from 7 to 22 m s 1 were examined winds from the southeast prevailed from one to several days with significant wave heights of 5 9 m and turbulent langmuir numbers of about 0 2 0 4 surface buoyancy forcing was much weaker than the wind stress forcing the water column was well mixed to the bottom depth of about 73 m spectral analyses indicate that a major part of the turbulent momentum flux was concentrated on 10 30 min time scales the ratio of horizontal scale to mixed layer depth was from 2 to 8 turbulent shear stresses in the mixed layer were horizontally asymmetric the downwind turbulent stress at 10 20 m below the surface was approximately 40 of the averaged wind stress and was reduced to 5 10 of the wind stress near the bottom turbulent kinetic energy in the cros

global distribution composition and abundance of olivine on the surface of mars from thermal infrared data 1 we used spectral indexing and linear deconvolution to compare thermal infrared emission spectra of fo91 fo68 fo53 fo39 fo18 and fo1 olivine samples to mars global surveyor thermal emission spectrometer tes data over low albedo regions of mars the fo91 fo68 fo53 and fo39 spectral end members were confidently identified on mars a range of compositions wider than inferred from martian meteorites small less than hundreds of square kilometers occurrences of the fo91 spectral end member are present in the rims of the argyre and hellas impact basins and may represent martian mantle materials the fo68 spectral end member is common throughout the highlands chasmata outflow channels and nili fossae region the fo53 spectral end member occurs in eastern syrtis major the nili fossae region and smooth floored craters of the highlands although less abundant than fo68 and fo53 the distribution of the fo39 spectral end member suggests that some olivine on mars is more fe rich than olivine in martian meteorites global maps of olivine show that 1 materials containing 10 20 of olivine are common in the southern highlands of mars 2 olivine is most common near the topographic dichotomy boundary and 3 olivine becomes uncommon near the poles suggesting that it may be influenced by topography and or latitude climate olivine is found in early noachian to amazonian terrains some of which may be coeval with phyllosilicate and sulfate deposits detected by omega implying that any early noachian wet period of mars climate history may have been globally inhomogeneous or insufficient to weather the olivine that remains today

mineralogical and spectroscopic investigation of enstatite chondrites by x ray diffraction and infrared reflectance spectroscopy 1 the mineralogy and infrared reflectance spectra of 13 enstatite e chondrite meteorite finds spanning the full range of textural alteration grades in both el and eh classes have been investigated rietveld refinement of high resolution powder x ray diffraction xrd data was used to determine quantitative major mineral abundances sample correlated mid infrared 2 0 to 25 0 m 4500 cm 1 to 400 cm 1 reflectance infrared spectra were collected for each meteorite spectral features due to the fundamental lattice vibrations of the silicates primarily enstatite dominate the spectra of these meteorites over most of the spectral range investigated the spectral features related to primary i e pre terrestrial mineralogy include fundamental stretching and bending lattice modes 8 3 25 0 m 1200 400 cm 1 overtones and combinations of the fundamental modes 4 5 6 1 m 2200 1650 cm 1 and the principle christensen feature 8 3 m 1200 cm 1 terrestrial weathering products including fe oxyhydroxides gypsum and carbonates occur in most of these meteorites and contribute to some spectral features particularly an asymmetric feature near 2 6 to 3 8 m 3800 to 2600 cm 1 attributed to adsorbed hydrogen bonded and or structural oh and h 2 o and a feature near 6 2 m 1625 cm 1 attributed to adsorbed hydrogen bonded and or structural h 2 o modal mineral abundances determined by rietveld refinement have been used to calculate model grain densities for each meteorite bulk magnetic susceptibility measurements combined with modal mineralogy and grain densities reveal a trend toward lower grain density and lower bulk susceptibility with increased terrestrial weathering

thermal infrared emissivity of felsic rich to mafic rich analogues of hot planetary regoliths abstract inner solar system bodies with absent or extremely tenuous atmospheres such as mercury and several high eccentricity near earth objects neos are subject to a wide range of surface temperatures here we show how the thermal expansion induced by strong diurnal insolation variations affects the thermal infrared spectra of felsic rich to mafic rich regoliths 1400 700 cm 1 spectra of granular plagioclase pyroxene mixtures were measured in the laboratory at four temperatures between 425 k and 725 k simulating different daily surface temperatures within the solar system at the same time we describe for the first time how two minerals with different thermal expansion coefficients combined in the same granular sample appear in a non ambient i e non 298 k thermal infrared spectrum the spectra of plagioclase rich analogues appear to be dominated by felsic features regardless of the daily surface temperature and do not exhibit any of the short wavelength absorptions of pyroxenes when detectable on the other hand the 870 cm 1 pyroxene absorption which is not affected by thermal variations functions instead as a proxy for the solid solution composition i e the mg fe relative contents in contrast indications of the plagioclase solid solution occurring at ambient temperatures i e ca na relative contents disappear at temperatures over 525 k christiansen feature position and spectral contrast which show a clear dependency on composition even at high temperatures require an accurate reproduction of the shallow thermal gradient in order to be used as indices in general in order to decipher planetary hyperspectral data surface temperature acquisition seems to be a prerequisite as well as a comparison with analogue spectra obtained under realistic environmental conditions

three dimensional langmuir circulation instability in a stratified layer some reports of langmuir circulations describe windrows at systematic angles to the local wind direction other observers find windrows in close alignment to the wind direction but with a systematic drift sideways to the wind these effects probably result from more than one physical cause here it is shown by an analysis of the linear stability of the surface layer averaged to remove surface wave fluctuations that persistent small windrow angles can result from weak stable density stratification in these cases the linearly most unstable modes are found to be weakly three dimensional for the range of parameters considered possible surface windrow patterns include rolls mostly parallel to the wind but of finite length with branching and merging as well as parallel rolls inclined to the wind and drifting laterally with respect to the wind direction for unstratified flow steady two dimensional rolls are preferred

the breakup of langmuir circulation and the instability of an array of vortices abstract the presence and pattern of langmuir circulation can be detected using side scan sonar the circulation creates bands of subsurface bubbles scatterers of high frequency sound in the downwelling region beneath the surface convergence the bands are clearly visible in sonographs a common process of development is for them to join in pairs the stability of the circulation pattern is examined making a number of simplifying assumptions in particular we represent the langmuir cells as linear vortices these are subjected to small disturbances when these are restricted to two dimensional motions normal to the axes of the vortices stable modes are found in part of the parameter range in which the windrow separation is large in comparison to an appropriate depth scale such as the depth of the vortex core in a very deep mixed layer or the depth of the thermocline or lake when this is finite these modes are destabilized to collective instabilities when three dimensional motions are permitted the

experimental petrology of the mars pathfinder rock composition constraints on the interpretation of martian reflectance spectra 1 experiments to determine the crystallization sequence of the mars pathfinder mpf rock composition have been carried out to explore the range of possible mineral assemblages in this sio2 rich 57 4 wt martian igneous rock recent mars global surveyor thermal emission spectrometer observations have suggested the presence of large volumes of andesitic lava covering the northern hemisphere of mars but this interpretation has been called into question experimentally produced mineral assemblages can be used to infer spectral characteristics that would exist in andesitic lavas similar in composition to the mpf rock the inferred spectra could then be used with remotely sensed data to further constrain the identity of surface rock types on mars we performed a series of experiments at 0 1 mpa at the quartz fayalite magnetite and iron quartz fayalite oxygen buffers and 100 mpa at the ni nio oxygen buffer using the calculated soil free mpf composition potential mineralogies for a lava with the mpf composition would be sio2 57 wt feo 18 wt rich glass plagioclase quartz augite and fe ti oxides a contoured pyroxene quadrilateral with band i and ii minima was used to predict pyroxene composition on the basis of reflectance spectra using the quadrilateral in reverse the augite produced in the experimental series should have band i and ii minima at 0 97 m and 2 15 m respectively the absence of the 1 m minima in the imager for mars pathfinder imp spectra could be due to masking phases possibly the fe ti oxides produced in our experiments at 1000 c

evidence for magma carbonate interaction beneath syrtis major mars 1 we used three methods spectral index mapping linear spectral mixture analysis and factor analysis and target transformation to determine if carbonate decomposition products including lime cao periclase mgo portlandite ca oh 2 and brucite mg oh 2 are present on the surface of mars using an expanded spectral library that includes decomposition products of calcite and magnesite we deconvolved a binned emissivity data set from the mars global surveyor thermal emission spectrometer mgs tes the deconvolution model indicates that anhydrous carbonates are not present at kilometer scales above the tes detection limit however carbonate decomposition products may be present at or above the tes detection limit in northeast syrtis major and several other small regions on mars the model results are supported by spectral index mapping and factor analysis and target transformation of tes data in this region the volcanic setting of the detections may indicate the interaction of syrtis major lavas with subsurface carbonates or alternatively the eruption of carbonate bearing lavas that were subsequently devolatilized by impacts or later lava flows

evidence for locally derived ultramafic intracrater materials in amazonis planitia mars 1 we studied a dark intracrater feature in amazonis planitia using visible thermal and spectral data from the mars global surveyor mgs thermal emission spectrometer tes mgs mars orbiter camera moc and 2001 mars odyssey thermal emission imaging system ody themis instruments visible and thermal data indicate that there are heterogeneities within the dark feature at meter to kilometer scales and suggest that it represents eroded terrain containing inactive ripple like bed forms possibly armored or indurated as well as loose possibly actively saltating sediment in addition part of the dark intracrater material may be covered with dust either as an optically thin few microns thick layer or as thicker discontinuous patches the thermal properties of the dark material are consistent with a mixture of sand rock and bedrock whereas the rest of the crater floor has thermal characteristics of fine 35 m particulates spectral data indicate that the crater floor is covered by a layer of dust that is spectrally and compositionally similar to the globally homogenized surface dust in other high albedo regions on mars the mineralogy of the dark materials is mafic dominated modally by pyroxene and olivine however unlike other lithologies common in low albedo regions i e surface types i and ii its derived bulk chemistry indicates that it is an ultramafic lithology with the lowest silica content detected on mars to date sheet silicates and glasses are not identified above detection limits and as such the materials do not display evidence for significant chemical weathering the geomorphology and visible distribution of the dark intracrater materials combined with the lack of an obvious source in the region outside the crater suggest they are the product of erosion of a local source

organic sedimentary deposits in titan s dry lakebeds probable evaporite we report the discovery of organic sedimentary deposits at the bottom of dry lakebeds near titan s north pole in observations from the cassini visual and infrared mapping spectrometer vims we show evidence that the deposits are evaporitic making titan just the third known planetary body with evaporitic processes after earth and mars and is the first that uses a solvent other than water

titan s inventory of organic surface materials 1 cassini radar observations now permit an initial assessment of the inventory of two classes presumed to be organic of titan surface materials polar lake liquids and equatorial dune sands several hundred lakes or seas have been observed of which dozens are each estimated to contain more hydrocarbon liquid than the entire known oil and gas reserves on earth dark dunes cover some 20 of titan s surface and comprise a volume of material several hundred times larger than earth s coal reserves overall however the identified surface inventories 3 104 km3 of liquid and 2 105 km3 of dune sands are small compared with estimated photochemical production on titan over the age of the solar system the sand volume is too large to be accounted for simply by erosion in observed river channels or ejecta from observed impact craters the lakes are adequate in extent to buffer atmospheric methane against photolysis in the short term but do not contain enough methane to sustain the atmosphere over geologic time unless frequent resupply from the interior buffers this greenhouse gas at exactly the right rate dramatic climate change on titan is likely in its past present and future

role of langmuir circulation in the deepening of the ocean surface mixed layer helical motions known as langmuir circulation are a key physical process in the upper ocean but have not yet been incorporated into ocean models here surface mixed layer deepening by langmuir circulation was added to that due to convection or velocity shear langmuir circulation is more important than shear if the velocity difference across the mixed layer base is less than about 1 percent of the wind speed in an upper ocean data set evidence was found for the deepening of the mixed layer by both mechanisms thus langmuir circulation influences upper ocean diurnal and seasonal changes in stratification

rapid and extensive surface changes near titan s equator evidence of april showers although there is evidence that liquids have flowed on the surface at titan s equator in the past to date liquids have only been confirmed on the surface at polar latitudes and the vast expanses of dunes that dominate titan s equatorial regions require a predominantly arid climate we report the detection by cassini s imaging science subsystem of a large low latitude cloud system early in titan s northern spring and extensive surface changes spanning more than 500 000 square kilometers in the wake of this storm the changes are most consistent with widespread methane rainfall reaching the surface which suggests that the dry channels observed at titan s low latitudes are carved by seasonal precipitation

effects of temperature on remotely sensed mineral absorption features laboratory spectral reflectance of mafic silicates has been measured over a temperature range characteristic of solar system objects to study the variation of diagnostic mineral absorption bands this information has become increasingly important with recent improvements in the quality of remotely sensed planetary data and the concurrent increase in sophistication of quantitative and qualitative spectrum analysis techniques in this study visible and near ir reflectance spectra 0 4 2 5 m of pyroxenes and olivine were obtained over a sample temperature range of 80 448 k these are the first published reflectance data for these minerals at temperatures significantly below ambient 300 k additionally thermal radiation emitted from the samples at elevated temperatures was effectively removed disclosing for the first time the high temperature reflectance behavior of pyroxenes in the diagnostic 2 m spectral region as expected from basic physical considerations fe2 crystal field absorptions in all samples become narrower with decreasing temperature the three components of the composite olivine band centered near 1 m become better resolved with decreased temperature and show changes in relative absorption strength there is not however any significant wavelength shift of the olivine reflectance minimum both orthopyroxene and clinopyroxene spectra show dramatic changes in band symmetry with temperature with the greatest change in the longer wavelength edge despite these significant changes in shape little if any change is observed in the wavelength position of reflectance minima of pyroxene absorptions near 1 m the 2 m pyroxene absorptions in contrast demonstrate major shifts of reflectance minima but in different directions in orthopyroxene spectra the band shifts to longer wavelengths with increased temperature while for the clinopyroxene spectra the band shifts to shorter wavelengths this behavior results in greatly improved spectral differentiation of orthopyroxene and clinopyroxene components in a mixture such as a basalt at reduced temperatures application of the results presented here to remote sensing mineral characterization techniques currently in use for determination of pyroxene composition can provide a moderate improvement to quantitative interpretations from 5 to 20 wt feo for orthopyroxenes and 5 wt cao for clinopyroxenes depending on planetary surface temperature

determining the modal mineralogy of mafic and ultramafic igneous rocks using thermal emission spectroscopy the modal mineralogies of 20 mafic and ultramafic igneous rocks were determined from their thermal infrared emission spectra using a linear deconvolution approach which uses a library of end member mineral spectra to model a bulk rock spectrum over 90 of the modes obtained from thermal emission spectra agree with modes obtained by traditional optical analyses to within the stated error of the optical analyses 5 15 vol library spectra of several compositions within a solid solution series e g plagioclase feldspars labradorite and bytownite were commonly used in each best fit model and are assumed to represent in combination a composition in the rock for which an identical mineral spectrum was unavailable in the library the accuracy of this assumption was evaluated by calculating a weighted average solid solution composition for plagioclase and or pyroxenes from the library minerals used in the model best fit of 14 rocks and comparing these compositions to the actual chemistries measured by electron microprobe or the optically estimated an the derived solid solution compositions are generally within 10 15 an or mg of the measured composition modal data derived from the spectra via the deconvolution were summed and converted to weight percent wt oxides for comparison to standard bulk chemistry data sio2 al2o3 and na2o k2o were generally slightly overestimated and feo and mgo were typically slightly underestimated modes and wt oxides were plotted on standard rock type classification diagrams and provide broadly accurate classifications demonstrating that the linear deconvolution technique is successful at deriving useful mineralogical information from thermal infrared emission spectra of bulk rock samples furthermore convolution of the laboratory data to spectral resolutions comparable to remote sensing instruments specifically the mars global surveyor thermal emission spectrometer demonstrates only a 5 vol increase in modal uncertainty for minerals present in abundances 10 vol this study thus provides a strong foundation for the application of this technique to mafic igneous sample spectra from both laboratory and remote sensing instruments

patterns of bubble clouds organized by langmuir circulation abstract a commonly observed property of near surface bubble distributions is their collective organization into long rows aligned with the wind under the influence of langmuir circulation time series observations with sonars having fixed orientation reveal the temporal evolution of bubble distributions as they drift through the sonar measurement path here this concept is extended to provide a time sequence at 37 s intervals of two dimensional images generated by horizontally rotating sonars observations obtained during a storm in the strait of georgia show individual langmuir convergence zones as they evolve above the freely drifting sonar the resulting images are processed to generate a binary representation of the convergence zone patterns from which their orientation length spacing and other properties can be extracted although there is some angular spreading most convergence lines are aligned within 20 of the wind the spacing between convergence lines reveals a wide range of scales but