spectral mixture modeling a new analysis of rock and soil types at the viking lander 1 site a viking lander 1 image was modeled as mixtures of reflectance spectra of palagonite dust gray andesitelike rock and a coarse rocklike soil the rocks are covered to varying degrees by dust but otherwise appear unweathered rocklike soil occurs as lag deposits in deflation zones around stones and on top of a drift and as a layer in a trench dug by the lander this soil probably is derived from the rocks by wind abrasion and or spallation dust is the major component of the soil and covers most of the surface the dust is unrelated spectrally to the rock but is equivalent to the global scale dust observed telescopically a new method was developed to model a multispectral image as mixtures of end member spectra and to compare image spectra directly with laboratory reference spectra the method for the first time uses shade and secondary illumination effects as spectral end members thus the effects of topography and illumination on all scales can be isolated or removed the image was calibrated absolutely from the laboratory spectra in close agreement with direct calibrations the method has broad applications to interpreting multispectral images including satellite images

optical scattering properties of terrestrial varnished basalts compared with rocks and soils at the viking lander sites basalt flows at the pisgah volcanic field california are mantled by aeolian silt sized deposits the bright mantle is overlain by a dense pavement of basalt cobbles smoothed by aeolian abrasion and coated with glossy dark gray and red desert varnishes in contrast the two viking landing sites on mars lack desert pavements and rocks have glossy surfaces that in some cases are brighter than soils to pursue further the scattering characteristics of varnished basalt cobbles for comparison to mars rocks laboratory measurements of bidirectional reflectance 0 69 m center wavelength were made as a function of incidence and emission angle along the principal plane for varnished and fresh basalt surfaces the reflectance data fit with a scattering model that includes specular reflections from rough surfaces and volume penetration and reflection show that the red varnished surfaces have higher single scattering albedoes and higher surface roughness values than the dark gray varnished surfaces 0 56 and 0 42 21 and 17 respectively fresh cut surfaces have lowest values 0 40 and 6 results are consistent with observations made from thin sections for these surfaces and with field observations that show dark gray varnished surfaces are smoothed by exposure to wind abrasion dark red varnished surfaces tend to be rougher because they are embedded in the aeolian mantle and develop in a protected environment application of the model to atmospherically corrected radiometrically calibrated viking lander images 0 60 to 0 74 m shows that many rocks are smoother and have single scattering albedoes higher than soils 9 versus 27 0 71 versus 0 63 respectively results are consistent with a model in which rocks at the surface of mars become smoothed by aeolian abrasion and coated with atmospheric dust lack of desert pavement on mars is probably associated with a scarcity of cobbles and a lack of soil forming processes similar bright smooth coatings are expected at other locations on mars including the pathfinder ares vallis site

morphological effects of damming on lower zambezi river the zambezi river is the fourth largest river in africa after the congo nile and niger and it is the largest african river flowing into the indian ocean the lower zambezi in mozambique is influenced by the presence of two very large reservoirs kariba dam and cahora bassa dam that have modified the natural seasonal flows as well as the sediment balance and morphology of the river in particular downstream of the cahora bassa reservoir down to the delta no negligible effects are reported to take place such as local scour bank collapse and shoreline progressive erosion davies et al 2000 beilfuss and dos santos 2001 in order to quantify and possibly mitigate these effects a simplified numerical model of the sediment transport and erosion sedimentation phenomena along the lower zambezi has been developed capable to deal with the scanty and uncertain data available indeed besides the systematic flow records at the dam sites and few occasional measurements of turbidity and bottom granulometry only the digital elevation model dem of the river will be used for the model the objective of this paper is to predict the present and future effects of the presence of the kariba and cahora bassa dams on the downstream morphology integrating the few coarse and nonsimultaneous data somehow improving their overall quality the model reproduces the time and space propagation of the disturbances that confirm with more generality the qualitative response of the river to the constructions of dams anticipated by various geomorphologists in fact the reduction of waterflow seems to have an immediate effect downstream by initially fostering the sediment deposition subsequently the total interception of sediment by the dam slowly takes over and inverts this tendency a slightly smaller aggradation or slightly larger degradation rate with respect to the natural conditions no dams seems to represent the dominant effect of damming in the long term evolution of the lower zambezi

the martian surface as imaged sampled and analyzed by the viking landers the two viking landers touched down on the surface of mars in july and september of 1976 viking lander 1 renamed the mutch memorial station mms continued to operate for 3 martian years in chryse planitia the landing site is a rolling sparsely cratered plain impact crater size frequency distributions demonstrate that only meters of vertical erosion have occurred over the lifetime of the surface the site exhibits bedrock exposures numerous rocks excavated during cratering events indurated fine grained sediment blocky material mixed with dust and lithic fragments and aeolian drifts that overlie the blocky material and which probably accumulated during global dust storms lander 2 operated for approximately 2 martian years in utopia planitia a region subjected to volcanic impact aeolian and periglacial phenomena lander 2 is located west of the 100 km diameter crater mie on or near the distal end of the continuous ejecta deposits polygonal ground suggests that desiccation or freeze thaw processes have occurred the lander 2 site exhibits numerous rocks excavated from craters and exposed by erosion set in a matrix of crusty to cloddy sediment rare aeolian drifts overlie the crusty to cloddy material lander multispectral imaging of sediment exposures at both sites is best matched with iron rich claylike weathering products called palagonites the spectral characteristics are probably governed by thin deposits of dust from global and local dust storms darkest rocks have reflectance values that match iron rich igneous rocks although most rocks are covered with indurated coatings of the palagonitelike products chemical compositions of sediments at the two landing sites are strikingly similar suggesting an aeolian origin the compositions suggest an iron rich igneous source rock and are matched by an assemblage of clays and salts samples of blocky materials were found to have about 50 more cl and so3 than other samples implying cementation by salts the magnetic component in the sediment is silt sized or finer and may be maghemite or ultrafine grained hematite no indigenous organic compounds were found the materials were found to be highly reactive releasing o2 when h2o was added oxidizing organic nutrients on board the landers and fixing atmospheric co2 clay to silt sized particles were inferred for drift and crusty to cloddy materials no terrestrial samples have been found that replicate all the attributes of the viking samples approximately 10 m of h2o ice accumulated during both winters at lander 2 and each time evaporated over approximately 200 martian days thin layers of bright red dust from global and local dust storms accumulated at both sites during the first 2 martian years during the third winter strong winds generally scoured the mms site leaving behind a darker aeolian lag deposit bedrock at both sites formed billions of years ago and rocks have been generated and weathered slowly over geologic time but aeolian sediments accumulate become cemented and are subsequently eroded over time spans of millions of years or less the lifetime of the sedimentary deposits at the landing sites may be governed by the 105 to 106 year variations in climate due to quasi periodic changes in obliquity eccentricity and spin axis orientation

near infrared imaging of mars from hst surface reflectance photometric properties and implications for mola data abstract we report initial results from hubble space telescope hst images of mars obtained at a near ir wavelength of 1042 nm between february 1995 and june 1997 the images provide the highest spatial resolution global near ir measurements of mars obtained to date the data have been calibrated to radiance factor i f to an absolute accuracy of 2 to 5 including new refinements to several hst calibration parameters and now exist as a set of coregistered map projected images spanning a range of phase angles between 10 and 41 the relatively high spatial resolution 20 30 km pixel global maps when compared with viking era global albedo maps reveal that substantial variations in mars surface albedo patterns have occurred in the past 20 years the most obvious changes include several classical dark regions that have become substantially brighter and a few formerly bright regions that have darkened the normal albedo of typical surface regions in the near ir is derived from the multiple phase angle observations and is found to be bimodal with typical bright and dark values of 0 36 and 0 18 respectively the surface near ir phase coefficient ranges from 0 0 to 0 013 mag deg and there is no systematic correlation between phase coefficient and normal albedo this observation is consistent with the diffusely scattering nature of the martian atmosphere even during times of low dust opacity the data presented here may facilitate the planning and optimization of measurements to be obtained by the mars global surveyor mgs mars orbiter laser altimeter mola which will begin mapping the planet in 1999 these hst data also provide a basis for comparison with future mola and mars orbiter camera moc data in searches for seasonal and interannual variations in surface and polar cap albedo

the chemical composition of martian soil and rocks returned by the mobile alpha proton x ray spectrometer preliminary results from the x ray mode the alpha proton x ray spectrometer apxs on board the rover of the mars pathfinder mission measured the chemical composition of six soils and five rocks at the ares vallis landing site the soil analyses show similarity to those determined by the viking missions the analyzed rocks were partially covered by dust but otherwise compositionally similar to each other they are unexpectedly high in silica and potassium but low in magnesium compared to martian soils and martian meteorites the analyzed rocks are similar in composition to terrestrial andesites and close to the mean composition of earth s crust addition of a mafic component and reaction products of volcanic gases to the local rock material is necessary to explain the soil composition

on the spectral reflectance properties of materials exposed at the viking landing sites bidirectional reflectances calibrated to within 10 uncertainties for blue 0 40 0 52 m green 0 50 0 59 m and red 0 60 0 74 m channels were determined for 31 block and soil exposures imaged by the viking lander cameras reflectances were corrected for atmospheric attenuation by using optical depth measurements obtained by the lander cameras and for skylight illumination by subtracting the brightness values of adjacent shadowed areas reflectances for two facets on each of two large blocks were computed for a common geometry by determining facet orientations from high resolution lander stereo images and by fitting the hapke irvine photometric function to reflectances estimated for several geometries results indicate that individual facets on the same block have different optical properties the darkest grayest block facets have properties similar to laboratory reflectance spectra of mafic rocks that are thinly coated with ferric iron rich palagonite most block surfaces have reflectances consistent with thin to optically thick covers of palagonitic material limited exposures of soil have spectra that are also similar to palagonitic material the majority of the soils sampled and a few block surfaces have spectra with steeper slopes and greater spectral curvatures than the palagonite analog consistent with greater degree of ferric iron crystallinity the soils could be an intimate mixture of palagonitic material and other materials not seen in end member form but if so these other materials would need an even greater slope and curvature than observed soils the differences in reflectance properties for common block surfaces compared to common soils imply that local weathering of blocks has not contributed significantly to the soil exposed at the landing sites

preliminary results on photometric properties of materials at the sagan memorial station mars reflectance measurements of selected rocks and soils over a wide range of illumination geometries obtained by the imager for mars pathfinder imp camera provide constraints on interpretations of the physical and mineralogical nature of geologic materials at the landing site the data sets consist of 1 three small photometric spot subframed scenes covering phase angles from 20 to 150 2 two image strips composed of three subframed images each located along the antisunrise and antisunset lines photometric equator covering phase angles from 0 to 155 and 3 full image scenes of the rock yogi covering phase angles from 48 to 100 phase functions extracted from calibrated data exhibit a dominantly backscattering photometric function consistent with the results from the viking lander cameras however forward scattering behavior does appear at phase angles 140 particularly for the darker gray rock surfaces preliminary efforts using a hapke scattering model are useful in comparing surface properties of different rock and soil types but are not well constrained possibly due to the incomplete phase angle availability uncertainties related to the photometric function of the calibration targets and or the competing effects of diffuse and direct lighting preliminary interpretations of the derived hapke parameters suggest that 1 red rocks can be modeled as a mixture of gray rocks with a coating of bright and dark soil or dust and 2 gray rocks have macroscopically smoother surfaces composed of microscopically homogeneous clear materials with little internal scattering which may imply a glass like or varnished surface

overview of the mars pathfinder mission and assessment of landing site predictions chemical analyses returned by mars pathfinder indicate that some rocks may be high in silica implying differentiated parent materials rounded pebbles and cobbles and a possible conglomerate suggest fluvial processes that imply liquid water in equilibrium with the atmosphere and thus a warmer and wetter past the moment of inertia indicates a central metallic core of 1300 to 2000 kilometers in radius composite airborne dust particles appear magnetized by freeze dried maghemite stain or cement that may have been leached from crustal materials by an active hydrologic cycle remote sensing data at a scale of generally greater than 1 kilometer and an earth analog correctly predicted a rocky plain safe for landing and roving with a variety of rocks deposited by catastrophic floods that are relatively dust free

the imager for mars pathfinder experiment the imager for mars pathfinder imp a stereoscopic multispectral camera is described in terms of its capabilities for studying the martian environment the camera s two eyes separated by 15 0 cm provide the camera with range finding ability each eye illuminates half of a single ccd detector with a field of view of 14 4 14 0 and has 12 selectable filters the 18 optics have a large depth of field and no focussing mechanism is required a mechanical shutter is avoided by using the frame transfer capability of the 512 512 ccd the resolving power of the camera 0 98 mrad pixel is approximately the same as the viking lander cameras however the signal to noise ratio for imp greatly exceeds viking approaching 350 this feature along with the stable calibration of the filters between 440 and 1000 nm distinguishes imp from viking specially designed targets are positioned on the lander they provide information on the magnetic properties of wind blown dust measure the wind vectors and provide radiometric standard reflectors for calibration also eight low transmission filters are included for imaging the sun directly at multiple wavelengths giving imp the ability to measure dust opacity and potentially the water vapor content several experiments beyond the requisite color panorama are described in detail contour mapping of the local terrain multispectral imaging of the surrounding rock and soil to study local mineralogy viewing of three wind socks measuring atmospheric opacity and water vapor content and estimating the magnetic properties of wind blown dust this paper is intended to serve as a guide to understanding the scientific integrity of the imp data that will be returned from mars starting on july 4 1997

the scattering properties of natural terrestrial snows versus icy satellite surfaces abstract a j verbiscer and j veverka 1990 icarus 88 418 428 demonstrated that the single scattering properties of terrestrial snows are highly forward scattering in contrast to the single scattering properties of icy satellite surfaces which all have a backscattering component to their single scattering functions as modeled with b hapke s equations 1981 j geophys res 86 3039 3054 1984 icarus 59 41 59 1986 icarus 67 264 280 this study demonstrates to first order that the differences between the scattering properties of icy satellite regoliths and their terrestrial counterparts are due to differences in particle structure and textures we find that the particles of the regoliths of the icy satellites are composed of a complex mixture of grain textures and structures

results from the mars pathfinder camera images of the martian surface returned by the imager for mars pathfinder imp show a complex surface of ridges and troughs covered by rocks that have been transported and modified by fluvial aeolian and impact processes analysis of the spectral signatures in the scene at 440 to 1000 nanometer wavelength reveal three types of rock and four classes of soil upward looking imp images of the predawn sky show thin bluish clouds that probably represent water ice forming on local atmospheric haze opacity 0 5 haze particles are about 1 micrometer in radius and the water vapor column abundance is about 10 precipitable micrometers

nature and distribution of surficial deposits in chryse planitia and vicinity mars color images of bright red dust deposits at the mutch memorial station were acquired at variable incidence angles during sol 611 subsolar longitude 70 northern spring season after removing effects due to atmospheric scattering and absorption the data were used to estimate the independent variables in the hapke 1986 photometric function in blue green and red coordinates the vector representing the space radiance factor of the landing site extracted from viking orbiter images acquired on sol 609 is separated by a euclidean distance of only 0 022 units and an angle of only 1 5 from the vector estimated from the station data for the orbiter lighting and viewing geometries this result implies that light reflected from dust exposures dominates the orbiter signal multiplicative and additive atmospheric terms cancel one another and surface roughness is a second order effect in the orbiter data dust radiance factors computed from station data are most like laboratory spectra for fine grained hawaiian palagonite and are indistinguishable from earth based spectra of classical bright areas color composites of orbiter images show that the dust is found immediately south of acidalia planitia and in association with topographic barriers such as craters and cliffs examination of viking infrared thermal mapper data shows that the dust deposits typically do not have distinctive thermal inertia signatures implying that the deposits are optically thick hundreds of micrometers but thinner than the diurnal thermal skin depth centimeters dark gray material with thermal inertia values 8 12 10 3 cal cm 2 s 1 2 k 1 indicative of sand grain sizes 0 5 1 5 mm dominates the acidalia planitia lowlands and parts of kasei vallis this material also occurs as dark streaks extending from craters in xanthe terra and oxia palus space radiance factors of dark gray material are similar to spectra of mafic rock mixed with a minor amount of palagonitelike material material that is darker than but just as red as the dust deposits occurs in lunae planum xanthe terra and oxia palus areas of intermediate elevation multiple phase angle orbiter images suggest that the dark red exposures are a mixture of bright red and dark gray materials with the dark red exposures being relatively rough at a subpixel scale as compared to exposures of the other two materials thus only two types of materials can be detected in the data covering the study area palagonitelike dust and mafic rock fragments thermal inertia values 4 8 10 3 cal cm 2 s 1 2 k 1 for the dark red material are consistent with the presence of fine to medium sand size particles 0 10 0 5 mm such material should be easily moved by winds the lack of aeolian features implies that the dark red deposits are not composed of loose material rather they are probably more eroded versions of blocky soil or duricrust cemented dust and rock fragments exposed at the station both bright red dust aeolian suspension load and dark gray materials saltation traction loads migrate over the dark red substrate the overall distribution of the surficial units is controlled by topography at a variety of length scales lower wind threshold friction velocities associated with higher atmospheric densities in lowlands keep dust from accumulating and duricrust from forming while higher threshold velocities in highlands lead to net accumulation of dust local topographic obstacles craters walls ridges perturb wind flow and lead to local accumulation or erosion at a variety of elevations in addition the bright red dust ubiquitously found between exposures of dark gray and dark red materials may accumulate as the wind velocity gradient decreases at the transition from smoother dark gray exposures to rougher dark red exposures the distribution of the materials must also be modulated by climatic variations induced by quasi periodic oscillations in obliquity eccentricity and spin axis direction constraining these surficial deposits to be 1 ma

observational evidence of crystalline iron oxides on mars visible to near ir 0 4 1 0 mu m spectral reflectance observations of mars during the 1988 opposition were performed at mauna kea observatory using a circular variable filter spectrometer at a spectral resolution r lambda delta lambda approx 80 on august 13 and 14 1988 ut 41 regions 500 600 km in diameter were observed on mars the data have been reduced both to reflectance relative to solar analog mars 16 cyg b and to relative reflectance spot spot the spectra show the strong near uv reflectance dropoff characteristic of mars as well as absorptions at 0 62 0 72 mu m and 0 81 0 94 mu m both seen here clearly for the first time these absorption features are interpreted as fe sup 3 electronic transition bands that indicate the presence of crystalline ferric oxide or hydroxide minerals on the martian surface comparison of these data with laboratory spectra obtained by other workers supports the conclusion that a single iron oxide phase most likely hematite could account for all of the observed spectral behavior of the martian surface soils and airborne dust in the 0 4 1 0 mu m region this possibility must be reconciled with data from other possible spectral analogs and other wavelength regions as well as geochemical and mineral stability considerations to arrive at amore more complete understanding of the role of ferric minerals in martian surface mineralogy and weathering less

martian phase function modeling the visible to near infrared surface photometric function using hst wfpc2 data abstract images of mars in the visible to near infrared acquired from 1996 to 2005 using the hubble space telescope wfpc2 have been used to model the martian surface photometric function at 502 673 953 and 1042 nm these data range in spatial resolution from 12 to 70 km pixel at the sub earth point and in phase angle coverage from 0 34 to 40 5 the wfpc2 images have been calibrated to radiance factor or i f and projected to a cylindrical map for coregistration and comparison to similarly mapped spacecraft data sets of albedo topography thermal inertia composition and geology we modeled the observed i f as a function of phase angle using minnaert lambert lunar lambert and hapke photometric functions for numerous regions of interest binned into albedo units defined by viking and tes albedo maps and thermal inertia units defined by tes thermal inertia maps visibly opaque water ice clouds and data acquired under high dust opacity conditions were excluded from the analysis our modeling suggests that under average to low atmospheric dust opacity conditions and over this range of phase angles the photometric properties of the martian surface at 502 673 953 and 1042 nm are best modeled by lunar lambert functions with parameters derived for three surface units defined by low moderate and high tes bolometric albedos

photometric properties of phobos surface materials from viking images abstract clear filter viking images and an accurate numerical model of the shape of phobos have been used to determine this satellite s photometric properties a global average hapke function derived from disk resolved data confirms previous indications that phobos has a strong opposition surge photometrically corrected images were mosaicked into an albedo map most of the resulting normal reflectances are in the range 0 06 0 10 and the brightest region on phobos is the northeast rim of the crater stickney the portion of that rim with the highest concentration of grooves globally there are three albedo classes reasonably separated geographically 1 bright material is to the east and south of stickney corresponding approximately to the locations on phobos having the highest bluest visible near ir ratio murchie et al 1991 2 the darkest material is to stickney s west correlating with material having an intermediate visible nir ratio murchie et al s bluish gray unit 3 intermediate albedo material dominates the anti stickney hemisphere corresponding to material with a lower visible nir ratio murchie et al s reddish gray unit a search for variations in phase behavior across phobos surface shows few such effects overall limited to isolated areas 1 stickney s floor darkens with increasing phase faster than average phobos this crater floor is both slightly more backscattering and significantly rougher than the global average the latter effect may be related to the slumping hinted at in low resolution images of stickney 2 we confirm that in many cases the contrast between the bright rims of small craters and grooves and their surroundings drops noticeably with increasing phase phase angles in use 10 50 however these bright rims overall display a diversity of photometric behavior and are the most heterogeneous areas on phobos in terms of regolith properties 3 we confirm that dark deposits in the floors of smaller craters darken faster with increasing phase than their surroundings cf goguen et al 1978 and find that these deposits are more backscattering than average phobos isolated regions with unusual phase behavior occur on phobos but not on deimos thomas et al 1996 the variable photometric properties of phobos isolated craters and grooves and the association of global albedo features with stickney reinforce interpretations that phobos regolith is emplaced and modified by discrete cratering events and is not mixed horizontally by extensive downslope creep as is apparently the case on deimos

a comparison of mercurian reflectance and spectral quantities with those of the moon we have examined previously published earth based telescopic spectra of mercury with the goal of obtaining clues to the planet s surface composition the study has three parts first because of suggestions that mercury s crust may be anorthositic we compare near infrared spectra of mercury with spectra of lunar anorthosites the spectral slopes and lack of strong mineralogic absorption features make the mercurian spectra similar to spectra of lunar anorthosites second we compare albedo quantities for mercury and the moon computed from telescopically derived photometric parameters with the laboratory albedos of returned lunar samples the albedos calculated from the photometric parameters are much lower than those of lunar samples measured in the laboratory third the mercurian spectra are interpreted in terms of the current model for the reflectance of an iron bearing silicate regolith on an airless body recent steps toward quantifying this model permit estimates of the feo content and opaque mineral abundance of the surface to be made we find that the mercurian spectra least affected by telluric absorptions imply feo tio2 4

characterization of the martian surface deposits by the mars pathfinder rover sojourner sojourner the mars pathfinder rover discovered pebbles on the surface and in rocks that may be sedimentary not volcanic in origin surface pebbles may have been rounded by ares flood waters or liberated by weathering of sedimentary rocks called conglomerates conglomerates imply that water existed elsewhere and earlier than the ares flood most soil like deposits are similar to moderately dense soils on earth small amounts of dust are currently settling from the atmosphere

surface textural properties of icy satellites a comparison between europa and rhea abstract solar phase curves for rhea are presented using new telescopic opposition data along with voyager imaging observations two viable solutions were found to hapke s model 1986 icarus 67 264 280 which was used to describe this phase curve the porosity derived from the model s opposition parameters show that the optically active portion of rhea s regolith has a porosity between 80 and 95 which is slightly lower than the porosity seen on europa and higher than the porosity measured for the moon using similar methods the macroscopic roughness is comparable to that measured by verbiscer and veverka 1989 icarus 82 336 353 for rhea the single particle scattering functions found in this study are predominantly forward scattering which contradicts the results of verbiscer and veverka 1989

laser raman spectroscopy of varnished basalt and implications for in situ measurements of martian rocks earth based and orbital spectroscopy and viking lander data strongly suggest that rocks on mars are coated with indurated dust deposits rock coatings will influence mineralogical measurements to be acquired in situ from mars rovers and other surface missions in that most techniques will detect the coatings and or coatings plus underlying minerals in this paper we present results of experiments on varnished basalt cobbles from the lunar crater volcanic field nevada using laser raman spectroscopic microprobe measurements obtained with a 514 5 nm ar laser and irradiation spot sizes from 1 to 20 m measurements from thin sections and fresh unprepared rock surfaces clearly allow identification of igneous minerals varnish spectra acquired from thin sections as well as from unprepared exterior rock surfaces typically show broad peaks consistent with the fine grained nature of varnish and the dominance of manganese oxide and clay minerals several areas also show sharp raman peaks due to phosphates and anatase indicative of the heterogeneity of varnish deposits raman spectra taken through varnished rock surfaces reveal the mineralogy of coatings where varnish is 15 m in thickness and a combination of coatings and igneous minerals in areas with thinner varnish given the abundance of rock coatings observed at the viking and pathfinder landing sites results indicate that techniques such as raman spectroscopy and any others with comparable penetration depths will sample some combination of coatings and underlying rock materials the ability to make many in situ measurements across samples coupled with the ability to expose fresh rock surfaces will be needed to unambiguously characterize both the coatings and the rocks on mars from future landers and or rovers

transmission electron microscopy characterization of dislocations and slip systems in k lingunite implications for the seismic anisotropy of subducted crust in order to estimate the seismic anisotropy of subducted crust polycrystalline samples of kalsi3o8 klingunite 25 of the total subducted transformed sediments have been synthesized and deformed under the temperature and pressure conditions of the subducted slabs transmission electron microscopy tem characterizations of the recovered samples reveal that the microstructures are clearly dominated by 0 0 1 glide involving screw dislocations for this reason only 100 could be identified as glide planes the question of 0 0 1 slip on 110 remains open few 1 2 111 dislocations were observed gliding on 110 planes which implies that 1 2 111 110 is a harder slip system than those involving 0 0 1 slip the occurrence of sub grain boundaries suggests that diffusion and climb might be active under these conditions

chemical multispectral and textural constraints on the composition and origin of rocks at the mars pathfinder landing site rocks at the mars pathfinder site are probably locally derived textures on rock surfaces may indicate volcanic sedimentary or impact generated rocks but aeolian abration and dust coatings prevent unambiguous interpretation multispectral imaging has resolved four spectral classes of rocks gray and red which occur on different surfaces of the same rocks pink which is probably soil crusts and maroon which occurs as large boulders mostly in the far field rocks are assigned to two spectral trends based on the position of peak reflectance the primary spectral trend contains gray red and pink rocks maroon rocks constitute the secondary spectral trend the spatial pattern of spectral variations observed is oriented along the prevailing wind direction the primary spectral trend arises from thin ferric coatings of aeolian dust on darker rocks the secondary spectral trend is apparently due to coating by a different mineral probably maghemite or ferrihydrite a chronology based on rock spectra suggests that rounded maroon boulders constitute the oldest petrologic unit a flood deposit succeeded by smaller cobbles possibly deposited by impact and followed by aeolian erosion and deposition nearly linear chemical trends in alpha proton x ray spectrometer rock compositions are interpreted as mixing lines between rock and adhering dust a conclusion supported by a correlation between sulfur abundance and red blue spectral ratio extrapolations of regression lines to zero sulfur give the composition of a presumed igneous rock the chemistry and normative mineralogy of the sulfur free rock resemble common terrestrial volcanic rocks and its classification corresponds to andesite igneous rocks of this composition may occur with clastic sedimentary rocks or impact melts and breccias however the spectral mottling expected on conglomerates or breccias is not observed in any apxs analyzed rocks interpretation of the rocks as andesites is complicated by absence of a 1 m pyroxene absorption band plausible explanations include impact glass band masking by magnetite or presence of calcium and iron rich pyroxenes and olivine which push the absorption band minimum past the imager s spectral range the inferred andesitic composition is most similar to terrestrial anorogenic icelandites formed by fractionation of tholeiitic basaltic magmas early melting of a relatively primitive martian mantle could produce an appropriate parent magma supporting the ancient age of pathfinder rocks inferred from their incorporation in hesperian flood deposits although rocks of andesitic composition at the pathfinder site may represent samples of ancient martian crust inferences drawn about a necessary role for water or plate tectonics in their petrogenesis are probably unwarranted

near opposition martian limb darkening quantification and implication for visible near infrared bidirectional reflectance studies a nearly global coverage of the martian eastern hemisphere acquired under small phase angles and varying observational geometries conditions has been produced from 1988 opposition by spectral 0 5 1 m imaging data obtained at the pic du midi observatory in france from this data set the methodology presented here permits a systematic analysis of martian photometric behavior at a regional scale of 100 300 km in the visible and near infrared the quantification of limb darkening as a function of wavelength and surface albedo gives access in martian regional properties as a function of wavelength and surface albedo and results in the production of visible and near infrared geometric albedo maps a linear relation between the limb darkening parameter k and geometric albedo exists in the near infrared based on laboratory studies it suggests a spectral response of particulate type for the martian soil conversely in the visible the value of k parameter is 0 6 independent of albedo and is consistent with a single scattering photometric behavior in the surface layer however the observed change in the martian photometry from single to multiple scattering may be partially due to a large contribution of atmospheric scattering above 0 7 m in the absence of a multitemporal dataset analysis it must be emphasized that the present results are a priori only pertinent to the atmospheric and surface conditions existing on mars at the time of observation however this analysis may contribute to characterize some physical properties such as surface roughness in the near infrared for bright terrains k tends to 0 8 and agrees with the presence of very fine particulate materials photometry of dark areas is more irregular 0 48 k 0 64 and might result from surface roughness heterogeneities however a few dark areas reveal that k anomalous values in the range 0 7 0 8 may be caused by the presence of a coating of very fine materials or duricrust finally we evaluate the influence of reflectance geometrical effects on the multispectral and spectroscopic data of the martian surface

the lunar opposition surge observations by clementine abstract the clementine mission to the moon in 1994 provided the first multispectral observations of the lunar opposition surge below a few degrees the brightness of the moon increases more than 40 between solar phase angles of 4 and 0 the opposition effect exhibits a small wavelength dependence the surge is 3 4 larger at 0 41 m than at 1 00 m this result suggests that the principal cause of the lunar opposition surge is shadow hiding while coherent backscatter if present makes only a minor contribution the amplitude of the effect depends significantly on terrain the surge is about 10 greater in the lunar highlands this difference is attributed to textural variations between the two terrains the clementine measurements provide a new basis for deriving spectral geometric albedos phase integrals and bond albedos a value of 0 11 0 01 was found for the lunar bolometric bond albedo this value is at the low end of the historical published values but not as low as the recent result of 0 080 0 002

seasonal ice cycle at the mars phoenix landing site 2 postlanding crism and ground observations 1 the combination of ground observations from the mars phoenix lander and orbital data from the compact reconnaissance imaging spectrometer for mars crism provided a detailed view of the formation of late summer surface water ice at the landing site and surrounding regions crism observations of the landing site during and immediately after phoenix operations were analyzed to track the seasonal and diurnal ice cycles during the late spring to late summer and a nonlinear mixing model was used to estimate grain sizes and relative abundances of water ice and dust the surface around the phoenix landing site was ice free from late spring through midsummer although transient patches of mobile ices were observed in an 85 m diameter crater to the northeast of the landing site at the 10 km diameter heimdal crater located 10 km east of the landing site permanent patches of water ice were observed to brighten during the late spring and darken during the summer possibly as fine grained water ice that was cold trapped onto the ice during late spring sintered into larger grains or finally sublimated exposing larger grained ice crism spectra first show evidence of widespread ice during the night at solar longitude ls 109 9 sols before phoenix s surface stereo imager detected it crism spectra first show evidence of afternoon surface ice and water ice clouds after ls 155 after phoenix operations ended

thermally altered palagonitic tephra a spectral and process analog to the soil and dust of mars we studied six palagonitic soil samples ph 1 through ph 6 which were collected at 30 cm intervals from a lava slab on mauna kea hawaii the samples represent an alteration sequence caused by heating during emplacement of molten lava over a preexisting tephra cone they are both spectral and weathering alteration process analogs to the martian surface techniques employed included visible and near ir spectroscopy mossbauer spectroscopy and magnetic analysis the two samples collected from beyond 90 cm from the slab ph 5 and ph 6 did not see the transient heating event and are composed of coarse grained glassy basaltic hawaiitic particles some of which have been moderately palagonitized since formation of the cone in the late pleistocene the four samples closest to the slab ph 1 through ph 4 have been strongly altered in response to heating during its emplacement their iron oxide mineralogy is dominated by nanophase ferric oxide the sample adjacent to the slab ph 1 which would have seen the highest temperatures has a factor of 3 less h2o and contains crystalline hematite and magnetite in addition to nanophase ferric oxide lesser amounts of magnetite but not hematite are present in samples 30 cm ph 2 and 60 cm ph 3 from the slab the reflectivity spectra of samples ph 2 through ph 4 are similar to spectra of palagonites reported by other workers to be good mars visible to near ir spectral analogs the reflectivity spectrum of ph 1 is an even better spectral analog to mars in that it exhibits absorption features indicative of both nanophase and crystalline ferric oxides similar to several new martian telescopic data sets our sampling site may also be a process analog for mars in that heating episodes by volcanism and or impact cratering could produce crystalline ferric oxides from poorly crystalline palagonitic material thus localized thermal alteration events may provide a volumetrically important mechanism for the palagonitization of basaltic glass and the production of crystalline ferric oxides on mars

characterization and mapping of surface physical properties of mars from crism multi angular data application to gusev crater and meridiani planum the analysis of particle physical properties grain size shape and internal structure and its organization surface porosity roughness and grain size distribution provides information about the geological processes which formed and modified planetary surfaces crism compact reconnaissance imaging spectrometer for mars multi angular observations varied emission angles allow for the characterization of the surface scattering behavior which depends on the composition and on the material physical properties such as the grain size shape internal structure and the surface roughness after an atmospheric correction compensating mineral aerosol effects by the multi angle approach for retrieval of the surface reflectance from crism observations mars reco the surface reflectances at different geometries were analyzed by inverting the hapke photometric model depending on six parameters single scattering albedo 2 phase function terms macroscopic roughness and 2 opposition effects terms in this work surface photometric maps are created to observe the spatial variations of surface scattering properties as a function of geological units information regarding the single scattering albedo the particle phase function and the macroscopic roughness are provided at the crism spatial resolution 200 m pixel this article describes the application of this methodology to the data covering the mars exploration rover mer landing sites located at gusev crater and meridiani planum where orbital and in situ observations are available complementary orbital observations e g crism spectra thermal emission imaging system themis high resolution imaging science experiment hirise images were used for interpreting the modeled hapke photometric parameters in terms of physical properties which can be used to constrain the geological processes available mer in situ observations were used as ground truth to validate the interpretations of the hapke parameters varied scattering properties were observed within a crism observation 5 10 km suggesting that the surfaces are controlled by local geological processes e g volcanic resurfacing aeolian and impact processes rather than regional or global processes results are consistent with the in situ observations thus validating the approach and the use of photometry for the characterization of martian surface physical properties

disk resolved photometric analysis of european terrains abstract using hapke s photometric model we examined the photometric textures of a representative subset of the geologic units on europa defined by lucchitta and soderblom 1982 satellites of jupiter pp 521 555 university of arizona press tucson the individual units studied possess the same small mean photometric slope angle as that found by domingue et al 1991 icarus 90 30 42 for the entire disk with one major exception the particles composing the surfaces of most of the units have similar scattering properties however the single particle scattering functions of the two bright plains regions examined are very different from each other and from the other units if the bright plains units are geologically younger than the other units an aging process that affects the single particle phase functions and albedos is inferred in our previous study we concluded that the disk integrated photometric properties of europa could not be explained adequately by ion bombardment however a new study on the effects of ion irradiation on the optical properties of materials sack et al 1991 j geophys res e 96 2 17535 17539 renders this conclusion invalid

galileo photometry of asteroid 243 ida galileo imaging observations over phase angles 19 5 to 109 8 are combined with near opposition earth based data to derive the photometric properties of ida to first order these properties are uniform over the surface and well modeled at 0 55 m by hapke parameters 0 0 22 h 0 020 b0 1 5 g 0 33 and 18 with corresponding geometric albedop 0 21 0 030 01and bond albedoab 0 081 0 0170 008 ida s photometric properties are more similar to those of average s asteroids p helfenstein and j veverka 1989 asteroids ii univ of arizona press tucson than are those of 951 gaspra two primary color units are identified on ida terrain a exhibits a spectrum with relatively shallower 1 m absorption and a relatively steeper red spectral slope than average ida while terrain b has a deeper 1 m absorption and a less steep red slope the average photometric properties of ida and terrain a are similar while those of terrain b differ mostly in having a slightly higher value of 0 0 22 versus 0 21 suggesting that terrain b consists of slightly brighter more transparent regolith particles galileo observations of ida s satellite dactyl over phase angles 19 5 to 47 6 suggest photometric characteristics similar to those of ida the major difference being dactyl s slightly lower albedo 0 20 compared to 0 21