ventifacts at the pathfinder landing site about half of the rocks at the mars pathfinder ares vallis landing site appear to be ventifacts rocks abraded by windborne particles comparable resolution images taken by the imager for mars pathfinder imp camera and the viking landers show that ventifacts are more abundant at the pathfinder site the ventifacts occur in several forms including rocks with faceted edges finger like projections elongated pits flutes grooves and possible rills the trends of elongated pits flutes grooves and rills cluster at 280 330 clockwise from north and generally dip 10 30 away from their trend direction these orientations are indicative of southeast to northwest winds and differ from the trend of wind tails at the landing site the direction of local wind streaks and predictions of the global circulation model all of which indicate northeast to southwest winds the disparity between these data sets strongly suggests that local circulation patterns have changed since the abrasion of the ventifacted rocks the greater number of ventifacts at the pathfinder site compared to either of the viking sites is most easily explained as being due to a larger supply of abrading particles composed of either sand sized grains or indurated dust aggregates and higher surface roughness which should increase the momentum of saltating grains the pathfinder ventifacts may have formed shortly after the deposition of outflow channel sediments nearly 2 gry ago when a large local supply of abrading particles should have been abundant and atmospheric conditions may have been more conducive to rock abrasion from saltating grains based on how ventifacts form on earth the several ventifact forms seen at the pathfinder site and their presence on some rocks but not on others are probably due to local airflow conditions original rock shape exposure duration rock movement and to a lesser extent rock lithology the abundance of ventifacts at the pathfinder site together with other evidence of weathering indicates that unaltered rock surfaces are rare on mars

practical application of the sequential balancing technique an example from the irish variscides the process of sequential restoration presented by cooper trayner 1986 is applied to a n s cross section through the irish variscides to demonstrate that this approach improves the accuracy of thin skinned structural modelling and allows the progressive deformation of a marginal belt to be examined the principles and methods of sequential restoration are illustrated the cross section is restored in four steps and gives a bulk shortening of 52 in this model the fold belt evolved as the basal decollement migrated northwards and considerable ductile shortening by folding and cleavage formation preceded faulting although faulting gradually became more important towards the north the section is divided into four structural domains based upon different deformation histories each is restored independently by removing the ductile strain before restoring the faulting from this example it is clear that many models derived from single step balancing especially those through ductile deformed areas should be re examined

polar margin dunes and winds on mars the approximately concentric arrangement of layered deposits and dune fields at the two martian poles may reflect a nearly steady state dispersal of material from the polar deposits data on effective surface winds from high resolution viking images combined with theory of local winds suggest that the northern dunes are in part confined to a latitude band by winds generated by their own low albedo dispersal of the dark sand from the southern polar region is not subject to this kind of feedback because the irregular topography prevents areal accumulations sufficiently extensive to produce winds

microcraters on mars evidence for past climate variations mars climate models predict hundredfold or greater variations in the mass of the martian atmosphere due to large amplitude variations in mars obliquity through time the production rates of impact craters on the martian surface should be greatly affected by these atmospheric mass variations we have constructed a simulation of the meteor bombardment of mars which shows that during periods of the lowest theoretical atmospheric mass the production rates of centimeter sized hypervelocity impact craters are increased significantly these results imply that limited in situ observations of microcraters visible on martian rock faces could validate major aspects of the astronomical theory for climate change on mars

phoenix robotic arm camera 1 the phoenix robotic arm camera rac is a variable focus color camera mounted to the robotic arm ra of the phoenix mars lander it is designed to acquire both close up images of the martian surface and microscopic images down to a scale of 23 m pixel of material collected in the ra scoop the mounting position at the end of the robotic arm allows the rac to be actively positioned for imaging of targets not easily seen by the stereo surface imager ssi such as excavated trench walls and targets under the lander structure color information is acquired by illuminating the target with red green and blue light emitting diodes digital terrain models dtm can be generated from rac images acquired from different view points this can provide high resolution stereo information about fine details of the trench walls the large stereo baseline possible with the arm can also provide a far field dtm the primary science objectives of the rac are the search for subsurface soil ice layering at the landing site and the characterization of scoop samples prior to delivery to other instruments on board phoenix the rac shall also provide low resolution panoramas in support of ssi activities and acquire images of the lander deck for instrument and lander check out the camera design was inherited from the unsuccessful mars polar lander mission 1999 and further developed for the canceled mars surveyor 2001 lander msl01 extensive testing and partial recalibration qualified the msl01 rac flight model for integration into the phoenix science payload

hubble space telescope observations of the martian aphelion cloud belt prior to the pathfinder mission seasonal and interannual variations the presence of a globally extant equatorial belt of water ice clouds on mars is quantitatively investigated using data from three seasons of our hubble space telescope synoptic monitoring program 1993 1997 a subset of the 1996 1997 images covers the landing site of the mars pathfinder including a set of images taken after touchdown using multicolor imaging from the wide field planetary camera and the wide field planetary camera 2 we characterize both water ice cloud and dust optical depths as a function of latitude at several local times for each observing epoch the analysis technique models calibrated data using a multiple scattering radiative transfer code our results support the initial results of clancy et al 1996a regarding changes between the aphelion and perihelion climate of mars and provide a more detailed look at the development and decay of the cloud belt comparing our dust optical depths to those of the viking landers for the same seasons we note a trend toward lower dust loading in late northern winter and in spring our observations of the pathfinder site in july 1997 reveal a dust opacity in good agreement with that reported by pathfinder smith et al 1997b in addition the serendipitous occurrence of a dust storm in valles marineris in late june 1997 allows us to derive a set of dust single scattering albedos for use in more accurately modeling the dust s radiative properties and effects

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

mars pathfinder landing site evidence for a change in wind regime from lander and orbiter data surface features related to the wind are observed in the vicinity of the mars pathfinder mpf landing site data from the lander and in data from orbit by the viking orbiter and mars global surveyor missions features seen from the surface include wind tails associated with small rocks barchanoid duneforms ripplelike patterns and ventifact flutes cut into some rocks features seen from orbit include wind tails associated with impact craters ridges inferred to be duneforms and modified crater rims interpreted to have been eroded and mantled by windblown material the orientations of these features show two prevailing directions one is inferred to represent winds from the northeast which is consistent with strongest winds predicted by a general circulation model to occur during the martian northern winter under current conditions a second wind blowing from the ese was responsible for modifying the crater rims and cutting some of the ventifacts the two wind regimes could reflect a change in climate related to mars obliquity or some other unknown factor regardless of the cause the mpf area has been subjected to a complex pattern of winds and supply of small particles and the original surface formed by sedimentary processes from tiu and ares vallis flooding events has been modified by repeated burial and exhumation

viking landing sites remote sensing observations and physical properties of martian surface materials abstract important problems that confront future scientific exploration of mars include the physical properties of martian surface materials and the geologic processes that formed the materials the design of landing spacecraft roving vehicles and sampling devices and the selection of landing sites vehicle traverses and sample sites will be in part guided by the physical properties of the materials four materials occur in the sample fields of the viking landers 1 drift 2 crusty to cloddy 3 blocky and 4 rock the first three are soillike drift materials is weak loose and porous we estimate that it has a dielectric constant near 2 4 and a thermal inertia near 1 10 3 to 3 10 3 cal cm 2 sec 1 2 k 1 because of its low bulk density fine grain size and small cohesion crusty to cloddy material is expected to have a dielectric constant near 2 8 and a thermal inertia near 4 10 3 to 7 10 3 because of its moderate bulk density and cementation of grains blocky material should have a dielectric constant near 3 3 and a thermal inertia near 7 10 3 to 9 10 3 because of its moderate bulk density and cementation common basaltic rocks have dielectric constans near 8 and thermal inertias near 30 10 3 to 60 10 3 comparisons of estimated dielectric constants and thermal inertias of the materials at the landing sites with those obtained remotely by earth based radars and viking orbiter thermal sensors suggest that the materials at the landing sites are good analogs for materials elsewhere on mars correlation of remotely estimated dielectric constant and thermal inertias indicates two modal values for paired values of dielectric constants and thermal inertias near a 2 and 2 10 3 and b 3 and 6 10 3 respectively these two modes are comparable to the dielectric constants and thermal inertias for drift and crusty to cloddy material respectively dielectric constants and thermal inertias for blocky material are larger but conistent with values in the northern plains our interprertations are compatible with an aeolian origin for drift and similar materials elsewhere on mars the postulate that moderate dielectric constants and thermal inertias larger than 3 or 4 10 3 are produced by cementation of soillike materials is partly consistent with the data the average dielectric constant and thermal inertia and their correlation with one another suggest that most of the surface of mars should present few difficulties to future surface exploration but some surfaces may present difficulties for spacecraft that are not suitably designed

terrestrial analogs to wind related features at the viking and pathfinder landing sites on mars 1 features in the mojave desert and iceland provide insight into the characteristics and origin of martian wind related landforms seen by the viking and pathfinder landers the terrestrial sites were chosen because they exhibit diverse wind features that are generally well understood these features have morphologies comparable to those on mars and include origins by deposition and erosion with erosional processes modifying both soils and rocks duneforms and drifts are the most common depositional features seen at the martian landing sites and indicate supplies of sand sized particles blown by generally unidirectional winds erosional features include lag deposits moat like depressions around some rocks and exhumed soil horizons they indicate that wind can deflate at least some sediments and that this process is particularly effective where the wind interacts with rocks the formation of ripples and wind tails involves a combination of depositional and erosional processes rock erosional features or ventifacts are recognized by their overall shapes erosional flutes and characteristic surface textures resulting from abrasion by windblown particles the physics of saltation requires that particles in ripples and duneforms are predominantly sand sized 60 2000 m the orientations of duneforms wind tails moats and ventifacts are correlated with surface winds above particle threshold such winds are influenced by local topography and are correlated with winds at higher altitudes predicted by atmospheric models

the search for life on mars the role of rovers the search for evidence of life on mars will require highly capable rovers the strategy for the search for life divides into four major objectives understanding the history of the martian climate finding evidence of chemical evolution searching for evidence of past life and searching for evidence of living organisms to achieve these objectives rovers will need to traverse distances of the order of 10 km to study a variety of relevant features e g fluvial channels shorelines eskers hydrothermal deposits in sufficient detail to diagnose their formation processes requirements for rovers include color imaging at a range of spatial scales wide angle for geologic context high resolution for resolving millimeter to centimeter scale textures submillimeter resolution of selected areas in situ capabilities to perform chemical mineralogical and organic analysis and the ability to collect samples of rocks soils and subsurface samples for return to earth for detailed laboratory analysis simulations of rover missions to mars and the moon were performed for 3 days each in february 1995 using the marsokhod rover deployed on kilauea volcano hawaii and operated via satellite communications from moffett field california during the simulations science teams analyzed images taken by the marsokhod and deduced the geologic setting and history of the field site imaging for the mars mission simulation used mast mounted monochrome stereo cameras with 30 field of view 1 4 mrad pixel resolution 1 7 m height 1 m horizontal spacing and fixed pointing a camera mounted on a manipulator arm was capable of resolving 1 mm features during 18 hours of operation the rover traversed 800 m of terrain made observations at eight science targets and obtained 52 stereo images and 18 arm camera images for the lunar mission simulation stereo cameras were mounted on a mast with a pointable platform at 1 5 m height and 10 cm horizontal spacing stereo color video was transmitted to mission operations command cycles with 1 5 s time delay allowed live teleoperation in 15 hours of operation the rover traversed 1 2 km and nine science targets were studied in detail these experiments show that rovers can be used to successfully perform field geology on other planets

irish carboniferous conodonts record maturation levels and the influence of tectonism igneous activity and mineralization organic maturation patterns in the lower carboniferous of ireland have been determined from conodont colour alteration indices cai for some 750 localities onshore ireland conodonts record increasing maturation in the carboniferous rocks from the oil window rocks of the north east southwards to the greenschist meta argillite regime of the munster basin in detail the caledonoid trend has a marked influence in the midlands whilst in the south sharp variations in cai are interpreted as being caused by thrusting of the variscan orogeny in the south east low maturities in the wexford half graben indicate that the region was shielded from orogenic stresses probably by the leinster massif igneous centres such as the carlingford complex and croghan hill produce local sites of increased palaeotemperature significant cai variations have also been noted in proximity to major base metal orebodies the cai results highlight north east ireland and the wexford half graben as areas with hydrocarbon potential

origins of marslike spectral and magnetic properties of a hawaiian palagonitic soil a palagonitic soil hwmk1 from mauna kea hawaii has marslike spectral and magnetic properties reflectivity spectra of 20 m size separates resemble spectra for martian bright regions and reflectivity spectra of coarser size separates have some spectral characteristics in common with spectra for martian dark regions the bulk soil is magnetic with a saturation magnetization of 0 98 a m2 kg of sample 10 a m2 kg of fe at 296 k petrographic observations show that the soil contains separate populations of black and orange tephra particles which are relatively unaltered fragments of tachylite merocrystalline basalt and extensively weathered palagonitized fragments of sideromelane clear brown basalt glass respectively although both types of particles contain plagioclase and olivine microphenocrysts their iron oxide mineralogies are substantially different as documented by mossbauer and static magnetic measurements a strongly magnetic opaque iron oxide titanomagnetite is associated with black particles and is responsible for the magnetic nature of the soil a relatively weakly magnetic superparamagnetic ferric oxide and minor hematite are associated with orange particles and are responsible for the color the more highly weathered state higher state of oxidation of orange particles is a consequence of the faster weathering palagonitization rate for their sideromelane precursors than for tachylite increasing state of oxidation decreasing saturation magnetization and increasing near ir reflectivity with decreasing particle diameter of bulk soil are manifestations of the increasing proportions of palagonitic material as particle diameter decreases

low abundance materials at the mars pathfinder landing site an investigation using spectral mixture analysis and related techniques abstract recalibrated and geometrically registered multispectral images from the imager for mars pathfinder imp were analyzed using spectral mixture analysis sma and related techniques sma models a multispectral image scene as a linear combination of endmember spectra and anomalous materials which do not fit the model are detected as model residuals while most of the imp data studied here are modeled generally well using bright dust gray rock and shade image endmembers additional anomalous materials were detected through careful analysis of root mean square rms error images resulting from sma for example analysis of sma fraction and rms images indicates spectral differences within a previously monolithologic dark soil class a type of dark soil that has high fractional abundances in rock fraction images gray rock soil was identified other anomalous materials identified included a previously noted black rock lithology a class of possibly indurated compacted or partially cemented soils intermediate soil and a unit referred to as anomalous patches on at least one rock the black rock lithology has a strong 900 1000 nm absorption and modeling of the derived image endmembers using a laboratory reference endmember modeling rem approach produced best fit model spectra that are most consistent with the presence of high ca pyroxenes and or olivine crystalline ferric oxide minerals or mixtures of these materials as important components of the black rock endmember more unique mineralogic identifications could not be obtained using our initial rem analyses both intermediate soil and anomalous patches units exhibit a relatively narrow 860 950 nm absorption that is consistent with the presence of either low ca pyroxenes or a cementing crystalline ferric oxide mineral

determination of the chemical composition of martian soil and rocks the alpha proton x ray spectrometer the alpha proton x ray spectrometer apxs for the mars pathfinder mission is designed to provide a complete and detailed analysis of chemical elements in martian soil and rocks near the landing site the apxs instrument is carried on the pathfinder microrover which will provide transportation to places of interest on the martian surface it consists of a complex sensor head mounted on a simple but sophisticated apxs deployment mechanism adm outside the warm electronics box web of the microrover and the instrument electronics mounted inside the web the adm permits the instrument sensor head to be placed against soil and rock samples in arbitrary positions ranging from horizontal to vertical in order to perform in situ analysis the possibility to transport the apxs to an arbitrary location preselected on earth and to perform in situ analysis there constitutes one of the most exciting aspects of the pathfinder mission the principle of the apxs technique is based on three interactions of alpha particles from a radioisotope source with matter simple rutherford backscattering production of protons from p reactions on light elements and generation of characteristic x rays upon recombination of atomic shell vacancies created by a bombardment measurement of the intensities and energy distributions of these three components yields information on the abundance of chemical elements in the sample in terms of sensitivity and selectivity data are partly redundant and partly complementary alpha backscattering is superior for light elements c o while proton emission is mainly sensitive to na mg al si s and x ray emission is more sensitive to heavier elements na to fe and beyond a combination of all three measurements enables determination of all elements with the exception of h and he present at concentration levels above typically a fraction of 1

the state and future of mars polar science and exploration as the planet s principal cold traps the martian polar regions have accumulated extensive mantles of ice and dust that cover individual areas of 10 6 km 2 and total as much as 3 4 km thick from the scarcity of superposed craters on their surface these layered deposits are thought to be comparatively young preserving a record of the seasonal and climatic cycling of atmospheric co 2 h 2o and dust over the past 10 5 10 8 years for this reason the martian polar deposits may serve as a rosetta stone for understanding the geologic and climatic history of the planet documenting variations in insolation due to quasiperiodic oscillations in the planet s obliquity and orbital elements volatile mass balance atmospheric composition dust storm activity volcanic eruptions large impacts catastrophic floods solar luminosity supernovae and perhaps even a record of microbial life beyond their scientific value the polar regions may soon prove important for another reason providing a valuable and accessible reservoir of water to support the long term human exploration of mars in this paper we assess the current state of mars polar research identify the key questions that motivate the exploration of the polar regions discuss the extent to which current missions will address these questions and speculate about what additional capabilities and investigations may be required to address the issues that remain outstanding

a chronology of foreland deformation ultra violet laser 40ar 39ar dating of syn late orogenic intrusions from the variscides of southwest ireland abstract the upper palaeozoic sedimentary rocks of the munster and south munster basins southern ireland lie within the rhenohercynian zone of the european variscan orogeny this foreland region accommodated shortening during the asturian phase of variscan deformation at the end of the carboniferous by the development of kilometre scale and lower order folding high angle reverse faulting and regional fabric development at the southwestern extremity of the belt lies the black ball white ball heads area of the beara peninsula where high level igneous intrusions locally exhibit a close relationship with both the ductile and late brittle phases of variscan deformation 40 ar 39 ar ultra violet laser analysis of phlogopite crystals from these intrusions principally trachytic dykes has yielded ages that when combined with structural field relationships help to constrain the timing of variscan deformation in southern ireland these ages include 314 44 1 00 ma for a penetratively deformed lamprophric pipe on black ball head 301 98 1 47 298 08 0 61 ma for dyke material associated with later stage brittle deformation and a date of 296 88 0 60 ma for an undeformed post orogenic dyke on white ball head

mars pathfinder spectral measurements of phobos and deimos comparison with previous data the imager for mars pathfinder imp acquired four spectra of parts of the sub mars hemispheres of phobos and deimos the measured region of phobos is expected to be a mixture of the two spectral units identified on that satellite from phobos 2 data and the imp spectra of phobos are intermediate to the two units as expected the derived geometric albedo is consistent with the value for that part of phobos determined from viking imagery the imp spectrum of deimos is generally consistent with previous measurements acquired from the ground and from the hubble space telescope hst but the signal to noise ratio is lower than that of the phobos data the spectral contrast between the two moons is similar to that seen in hst and phobos 2 data mars pathfinder measurements therefore substantiate recent results which indicate that phobos and deimos are not as previously believed analogous to c type asteroids they also provide some indications for an absorption near 700 nm perhaps like that seen in other low albedo asteroids both martian moons are redder than most asteroids and most closely resemble two analog materials believed to have undergone very dissimilar histories primitive d like asteroids and highly space weathered mafic rich assemblages such as are present in lunar mare soils

techniques for identifying dust devils in mars pathfinder images image processing methods used to identify and enhance dust devil features imaged by imp imager for mars pathfinder are reviewed spectral differences visible red minus visible blue were used for initial dust devil searches driven by the observation that martian dust has high red and low blue reflectance the martian sky proved to be more heavily dust laden than pre pathfinder predictions based on analysis of images from the hubble space telescope as a result these initial spectral difference methods failed to contrast dust devils with background dust haze imager artifacts dust motes on the camera lens flat field effects caused by imperfections in the ccd and projection onto a flat sensor plane by a convex lens further impeded the ability to resolve subtle dust devil features consequently reference images containing sky with a minimal horizon were first subtracted from each spectral filter image to remove camera artifacts and reduce the background dust haze signal once the sky flat preprocessing step was completed the red minus blue spectral difference scheme was attempted again dust devils then were successfully identified as bright plumes false color ratios using calibrated imp images were found useful for visualizing dust plumes verifying initial discoveries as vortex like features enhancement of monochromatic especially blue filter images revealed dust devils as silhouettes against brighter background sky experiments with principal components transformation identified dust devils in raw uncalibrated imp images and further showed relative movement of dust devils across the martian surface

athena microscopic imager investigation 1 the athena science payload on the mars exploration rovers mer includes the microscopic imager mi the mi is a fixed focus camera mounted on the end of an extendable instrument arm the instrument deployment device idd the mi was designed to acquire images at a spatial resolution of 30 microns pixel over a broad spectral range 400 700 nm the mi uses the same electronics design as the other mer cameras but has optics that yield a field of view of 31 31 mm across a 1024 1024 pixel ccd image the mi acquires images using only solar or skylight illumination of the target surface a contact sensor is used to place the mi slightly closer to the target surface than its best focus distance about 66 mm allowing concave surfaces to be imaged in good focus coarse focusing 2 mm precision is achieved by moving the idd away from a rock target after the contact sensor has been activated the mi optics are protected from the martian environment by a retractable dust cover the dust cover includes a kapton window that is tinted orange to restrict the spectral bandpass to 500 700 nm allowing color information to be obtained by taking images with the dust cover open and closed mi data will be used to place other mer instrument data in context and to aid in petrologic and geologic interpretations of rocks and soils on mars

low temperature reflectivity spectra of red hematite and the color of mars reflectivity spectra visible and near ir were measured near 141 210 and 300 k for four red and well crystalline powders of hematite red hematite used as commercial pigments two samples of volcanic tephra from mauna kea volcano that contain red hematite as their dominant pigment three samples of palagonitic tephra from the same location that contain nanophase ferric oxide as their dominant pigment and two mixtures of the two types of pigmenting phases relative proportions of red hematite and nanophase ferric oxide were determined by mossbauer spectroscopy for samples containing red hematite as the dominant pigment the positions of the ferric electronic transitions near 430 500 630 and 860 nm are essentially independent of temperature but their widths decrease with decreasing temperature this decrease results in a well defined minimum for the band at 630 nm at low temperatures and in significant increases in reflectivity in spectral regions near 1050 and 600 nm for example the reflectivity ratios r 600 r 530 and r 600 r 860 both increase by a factor as large as l 4 between 300 and 140 k the spectral features from nanophase ferric oxide in samples of palagonitic tephra are nearly independent of temperature spectral data of martian bright regions that are characterized by a shallow band minimum near 860 nm a reflectivity maximum near 740 nm a distinct bend near 600 nm and a shallow absorption edge from 400 to 740 nm are attributed to the presence of nanophase ferric oxide plus subordinate amounts of red hematite the 600 740 and 860 nm features are associated with red hematite because the reflectivity of red hematite at 600 nm is strongly dependent on temperature and because this wavelength is in the red part of the visible spectrum the color of the martian surface may vary as a function of its temperature a conservative upper limit for the red hematite content of the optical surface of mars is 5

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

slope morphology of hills at the mars pathfinder landing site abstract the study of hillslopes is a primary element of geomorphology and has successfully been used in many terrestrial arenas in this study we take advantage of high resolution imaging science experiment hirise imagery as well as mars orbiter camera moc derived dems of the pathfinder landing site to study regional hillslopes at resolutions many times greater than previously available and compare them with mars pathfinder lander images this site was thought to be modified by massive flooding 1 8 3 5 byr ago and although evidence of flood activity was not obvious at the finer scale of this study possible lee deposits and terracing were seen in some of the features evidence of post flood processes of ice related creep aeolian and dry mass wasting were observed at the site and have likely obscured flood related morphology present in these features regional slopes were found to vary with aspect and suggest processes intensities operating at different orientations possibly related to the prevailing wind direction as well as the origin of the ancient flood event

precise dating of low temperature deformation strain fringe analysis by 40ar 39ar laser microprobe pyritized graptolites from the welsh basin united kingdom slate belt acted as rigid bodies during cleavage formation and epizonal white micas formed within the resulting strain shadows orthogonal to the principal stress orientation although the quantities of mica are small they are a pure synkinematic mineral and have been dated by ar 40 ar 39 infrared laser microprobe as a means to dating cleavage four samples of strain fringe mica from different hand samples yielded ages ranging from 394 4 3 1 to 397 8 1 8 ma 2sigma with a mean age of 396 1 1 4 ma 2sigma by focusing on minerals that are unequivocally synkinematic this technique provides a novel solution to the problems of isotopically dating slaty cleavage previous studies have predominantly relied on dating whole rock slate samples or separated illite grains by ar 40 ar 39 techniques problems encountered included 1 separating the effects of isotopic contamination by detrital phases 2 ar 39 loss during the irradiation of illite mineral separates and 3 thermally induced ar 40 loss in nature from fine grained minerals by circumventing these problems this new method provides the first unequivocal and high precision age data for acadian deformation in the well characterized welsh basin slate belt with such precision the method may afford geologists the opportunity to track tectonic fronts across orogens and assess the rates of accretion processes in areas that are peripheral to sites of continent continent collision

the mars pathfinder mission mars pathfinder one of the first discovery class missions quick low cost projects with focused science objectives will land a single spacecraft with a microrover and several instruments on the surface of mars in 1997 pathfinder will be the first mission to use a rover carrying a chemical analysis instrument to characterize the rocks and soils in a landing area over hundreds of square meters on mars which will provide a calibration point or ground truth for orbital remote sensing observations in addition to the rover which also performs a number of technology experiments pathfinder carries three science instruments a stereoscopic imager with spectral filters on an extendable mast an alpha proton x ray spectrometer and an atmospheric structure instrument meteorology package the instruments the rover technology experiments and the telemetry system will allow investigations of the surface morphology and geology at submeter to a hundred meters scale the petrology and geochemistry of rocks and soils the magnetic properties of dust soil mechanics and properties a variety of atmospheric investigations and the rotational and orbital dynamics of mars landing downstream from the mouth of a giant catastrophic outflow channel ares vallis at 19 5 n 32 8 w offers the potential of identifying and analyzing a wide variety of crustal materials from the ancient heavily cratered terrain intermediate aged ridged plains and reworked channel deposits thus allowing first order scientific investigations of the early differentiation and evolution of the crust the development of weathering products and the early environments and conditions on mars

rocks and aeolian features in the mars pathfinder landing site region viking infrared thermal mapper observations albedo rock abundance and thermal inertia derived from viking infrared thermal mapper observations provide information about the surface materials within the mars pathfinder landing ellipse in ares vallis relative to the rest of mars the site has an intermediate albedo 0 19 0 23 intermediate to high bulk thermal inertia 410 540 j m 2 s 0 5 k 1 and high rock abundance 18 25 at local scales the actual surface distribution of rocks might be heterogeneous as on terrestrial catastrophic flood surfaces where rocks tend to be concentrated on fluvially armored surfaces and or bars albedo increases and thermal inertia decreases from the northeast to the southwest in the ellipse owing to interpreted windblown dark sand from acidalia planitia if mars pathfinder lands at the southwest end of the landing ellipse the scene is likely to be the most similar to that of the viking 1 lander while a landing at the northeast end of the ellipse is most likely to provide a view that is different from the viking sites because of low albedo material a landing at the center of the ellipse might put the spacecraft near one of two crater clusters that are interpreted to have dark sandy material in or on their ejecta aeolian activity during the 30 day primary mission might be limited because it is mid northern summer a time in which no historic dust storms have been seen in the region and a season when regional winds should be weak relative to other times during the year

general geology and geomorphology of the mars pathfinder landing site the mars pathfinder mpf spacecraft landed on relatively young late hesperian early amazonian 3 1 0 7 ga plains in chryse planitia near the mouth of ares vallis images returned from the spacecraft reveal a complex landscape of ridges and troughs large hills and crater rims rocks and boulders of various sizes and shapes and surficial deposits indicating a complex multistage geologic history of the landing site after the deposition of one or more bedrock units depositional and erosional fluvial processes shaped much of the present landscape multiple erosional events are inferred on the basis of observations of numerous channels different orientations of many streamlined tails from their associated knobs and hills and superposition of lineations and streamlines medium and small scale features interpreted to be related to late stage drainage of floodwaters are recognized in several areas at the landing site streamlined knobs and hills seen in viking orbiter images support this inference as they seem to be complex forms partly erosional and partly depositional and may also indicate a series of scouring and depositional events that in some cases further eroded or partially buried these landforms although features such as these are cited as evidence for catastrophic flooding at ares vallis some of these features may also be ascribed to alternative primary or secondary depositional processes such as glacial or mass wasting processes close inspection of the landing site reveals rocks that are interpreted to be volcanic in origin and others that may be conglomeratic if such sedimentary rocks are confirmed fluvial processes have had a greater significance on mars than previously thought for the last several hundred million to few billion years eolian processes have been dominant dunes and dune like features ventifacts and deflation and exhumation features around several rocks probably are the most recent landforms the relatively pristine nature of the overall landscape at the mpf site suggests weathering and erosion processes on mars are exceptionally slow

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

a new structural model for the sw irish variscides the variscan front of the nw european rhenohercynian abstract the variscan front of nw europe has been drawn in the past from belgium across southern england and southern wales towards southern ireland but the term variscan front is not well defined and means different things to different people a tectonic front should represent the outcrop of a frontal thrust or the tip line of the basal detachment in fact such a tectonic front cannot be traced along the so called variscan front in ireland field based studies of the western part of the irish variscides show that the fold and thrust belt continues north of the so called variscan front but deformation decreases gradually therefore we suggest supported by seismic data a detachment which ends as a blind thrust far to the north the tip line of this basal detachment represents the true tectonic front of the variscides in sw ireland shear indicators show locally a dextral shear component near major faults and 3d microstructural strain analyses show varying x axes and oblate deformation indicating transpression during the tectonic evolution of the western irish variscides therefore a thin skinned model associated with dextral shearing and transpression in the hanging wall of the basal detachment is suggested the evolution of the variscan fold and thrust belt in nw europe is related to the west european indentation model but also to pre variscan basement structures as the leinster wales and london brabant massifs finally an attempt is made to outline the variscan front along the entire nw european rhenohercynian fold and thrust belt ftb

measurements of the atmospheric water vapor on mars by the imager for mars pathfinder the imager for mars pathfinder imp was the first instrument to measure the atmospheric water on mars from its surface it took the images of the sun through the martian atmosphere in five narrowband filters two in the 0 94 m h2o band and three in the continuum around it the observations were carried out in the mornings and in the evenings when the sun was between 3 and 8 above the horizon the absorption due to the atmospheric water vapor did not exceed 2 an average column density of 6 4 precipitated microns pr m was derived from the imp data the dependence of the observed h2o transmittance on sun elevation tentatively implies that the water vapor is not uniformly mixed in the atmosphere but is rather confined to a layer 1 3 km thick near the surface imp observations also indicate a horizontal inhomogeneity of the layer but show no significant morning to evening variations of the water vapor amount

soil like deposits observed by sojourner the pathfinder rover most of the soil like materials at the pathfinder landing site behave like moderately dense soils on earth with friction angles near 34 39 and are called cloddy deposits cloddy deposits appear to be poorly sorted with dust sized to granule sized mineral or rock grains they may contain pebbles small rock fragments and clods thin deposits of porous compressible drifts with friction angles near 26 28 are also present drifts are fine grained cohesions of both types of deposits are small there may be indurated soil like deposits and or coated or crusted rocks cloddy deposits may be fluvial sediments of the ares tiu floods but other origins such as ejecta from nearby impact craters should be considered drifts are probably dusts that settled from the martian atmosphere remote sensing signatures of the deposits inferred from rover observations are consistent with those observed from orbit and earth

structural evolution of the irish variscides the effects of the variscan orogeny on the upper palaeozoic succession are recognizable throughout central and southern ireland the deformation can be zoned using structural styles and trends which illustrate a northward decrease in deformation intensity coupled with increasing control by pre variscan structures in the basement the most intense deformation occurs to the south of the dingle dungarvan line where shortening approaches 50 as a result of layer parallel shortening followed by buckling and finally thrusting the deformation is considered to have developed above a shallow dipping sole thrust which has been located offshore by the swat seismic reflection profiles cross faults which are common throughout the orogen resulted from n s shear couples this is consistent with their origin as accommodation structures due to differential shortening along strike the original shape of the munster basin has exerted a control on the distribution and overall facing of the major structures the sole thrust extends to the north of the dingle dungarvan line and the structural zonation of the orogen is due to variations in the stratigraphic level of this thrust the leinster massif is considered to be essentially autochthonous slip on the sole thrust decays towards the massif which acted as a rigid passive block and was partially responsible for the arcuate trend of the orogen

overview of the mars pathfinder mission launch through landing surface operations data sets and science results mars pathfinder successfully landed at ares vallis on july 4 1997 deployed and navigated a small rover about 100 m clockwise around the lander and collected data from three science instruments and ten technology experiments the mission operated for three months and returned 2 3 gbits of data including over 16 500 lander and 550 rover images 16 chemical analyses of rocks and soil and 8 5 million individual temperature pressure and wind measurements path finder is the best known location on mars having been clearly identified with respect to other features on the surface by correlating five prominent horizon features and two small craters in lander images with those in high resolution orbiter images and in inertial space from two way ranging and doppler tracking tracking of the lander has fixed the spin pole of mars determined the precession rate since viking 20 years ago and indicates a polar moment of inertia which constrains a central metallic core to be between 1300 and 2000 km in radius dark rocks appear to be high in silica and geochemically similar to anorogenic andesites lighter rocks are richer in sulfur and lower in silica consistent with being coated with various amounts of dust rover and lander images show rocks with a variety of morphologies fabrics and textures suggesting a variety of rock types are present rounded pebbles and cobbles on the surface as well as rounded bumps and pits on some rocks indicate these rocks may be conglomerates although other explanations are also possible which almost definitely require liquid water to form and a warmer and wetter past air borne dust is composed of composite silicate particles with a small fraction of a highly magnetic mineral interpreted to be most likely maghemite explanations suggest iron was dissolved from crustal materials during an active hydrologic cycle with maghemite freeze dried onto silicate dust grains remote sensing data at a scale of a kilometer or greater and an earth analog correctly predicted a rocky plain safe for landing and roving with a variety of rocks deposited by catstrophic floods which are relatively dust free the surface appears to have changed little since it formed billions of years ago with the exception that eolian activity may have deflated the surface by 3 7 cm sculpted wind tails collected sand into dunes and eroded ventifacts fluted and grooved rocks pathfinder found a dusty lower atmosphere early morning water ice clouds and morning near surface air temperatures that changed abruptly with time and height small scale vortices interpreted to be dust devils were observed repeatedly in the afternoon by the meteorology instruments and have been imaged

morphologies of rocks within and near the rock garden at the mars pathfinder landing site this paper considers the morphology of several rocks and rock fragments within and near the rock garden at the mars pathfinder landing site we have analyzed stereo images taken both by the lander imp camera and by the rover forward cameras the rocks were found to differ in their roundness angularity and in their densities of millimeter to centimter sized pits and flute like features on the rock facets no correlation between rock roundness and the degree of rock pitting was found indicating that rounding and pitting formed by different processes pits are either gas bubbles implying the rocks are volcanic or resulted from eolian abrasion deflation putting no constraints on the nature of the rocks or both if pits are of eolian origin variations in the density of pits on different rocks imply that either the rock surfaces have been exposed for different times or the susceptibility of different rocks to pitting varies significantly from rock to rock implying differences in composition and or lithology the densities of pits and flutes on the rocks show anti correlation this may be connected to their formation but probably is mostly related to issues of observation and definition of what is a pit and what is a flute flute like features may be a result of eolian abrasion but in this case the spatial closeness of fluted rocks and those having delicately pitted textures requires explanation other mechanisms producing flute like features such as collisions in the deposit forming flows and the breaking of rock in impact cratering should not be ignored our observations agree with the conclusion of golombek et al this issue that deflational exhumation in this area was minor the observed relatively large rocks typically do not show a concentration of small rock fragments at their feet this implies diurnal thermal cycles are very ineffective at destructing rocks the rock half dome may be a conglomerate as suggested by smith et al 1997a for this and several other rocks but this hypothesis remains to be proven impact craters of a few meters to a few tens meters in diameter may have played a role in the local geology

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

vertical and horizontal heterogeneity of atmospheric dust loading in northern gale crater mars abstract this paper updates the record of atmospheric dust loading within northern gale crater mars by providing line of sight extinction los ext measurements of the intervening dust between the rover and the crater rim these measurements are derived from images taken with the navigation cameras navcam onboard the mars science laboratory msl rover curiosity the observations span 2 44 mars years from mars year my 31 at a solar longitude ls of 208 to t ls 7 of my34 sols 100 1701 of the msl surface mission this work examines the dataset for seasonal trends of the los ext in addition to horizontal variations and the vertical structure of los ext the los ext has a repetitive pattern with a single peak in the latter half of the mars year the atmosphere in the crater is well mixed horizontally but not vertically as larger los ext is seen nearer the crater floor than at higher altitudes within the crater the results allow a discussion on whether or not gale crater is a sink for atmospheric dust or a source of atmospheric dust in the current era

geology and genesis of manganese oolite chiatura georgia u s s r the oligocene stratiform manganese deposits in the chiatura region georgia soviet union were deposited on stable crystalline basement in a restricted arm of the paratethys during a transgressive regressive cycle transgression was characterized by in the early stages the development of a fining upward gravel and sand sequence and with increasing water depth deposition of organic rich fine grained sediments in waters increasingly depleted in oxygen manganese derived from weathering of recks surrounding the basin was probably concentrated in these reduced waters to levels well above those of normal sea water manganese carbonates were formed in offshore areas subject to reducing conditions in well aerated nearshore parts manganese oxides were formed landward migration of the oxidation reduction interface during transgression led to further concentration of manganese in nearshore regions and eventually to extensive precipitation and accumulation of manganese oxide ooliths and pisoliths occasionally in graded units during peak transgression and early regression when basin waters were reoxygenated late regression was characterized by the deposition of sands and spongiolite petrographic studies of manganese oxide ooliths and pisoliths indicate a concentrically laminated structure in which constituent pyrolusite microcrystals show a characteristic radial and less frequently random orientation with respect to the grain center ooliths and pisoliths which also exhibit micro unconformities and entrapped detrital material are considered to be analogous to some present day calcite and aragonite ooliths and were probably formed in a low energy shallow marine environment graded bedding in oolite and pisolite is comparable to similar beds documented in the cretaceous stratiform manganese deposit at groote eylandt in northern australia grading was probably formed as a result of changes in energy and or oxygen levels during small scale fluctuations in sea level

characteristics of the pathfinder apxs sites implications for the composition of martian rocks and soils an integrated study of spectral elemental abundance and image data from the pathfinder alpha proton x ray spectrometer apxs measurement sites has led to a better understanding of the nature of martian surface materials this rigorous analysis provides a new level of detail that forms the basis for the results reported here and that can be used by future scientists trying to understand rocks and soils on mars each apxs site has been precisely located by analyzing stereo imager for mars pathfinder imp and rover camera images to determine the position of the apxs during deployment rover and imp images are used to assess local geology namely the presence of pebbles clods and aeolian features in soils and surface textures and dust concentrations on rocks imp spectra using the latest calibrations for radiance and reflectance are analyzed at a number of different illumination geometries for each apxs site the three dimensional orientation of the sites has been determined and then used to compute the true sunlight incidence and viewing emission angles where suitable photometric coverage is available reflectances are fit to the hapke irvine function this is then used to adjust spectral reflectances to a normalized illumination geometry common to all rocks and soils comparing all the data sets shows a positive correlation among red blue reflectance ratio so3 content and dust abundance on rocks indicating that rocks are coated with varying amounts of sulfur rich red dust other elements such as silicon and iron are poor tracers for dust because their abundances within soil are similar to those within rock rock apxs targets that are bluer poorer in sulfur and have minimal dust coverage face toward the northeast the direction in which winds may be capable of efficiently removing loose material under current martian conditions the imp spectral properties of the soils show poor correlations with apxs elemental abundances on the basis of currently released apxs data bulk soils at the pathfinder landing site are richer in silica and sulfur than the viking landing sites suggesting a different composition the apxs soils with the most apparent pebbles are the poorest in sio2 indicating that either the pebbles are more mafic than the apxs rocks or the pebble free soil component is inherently enriched in sio2 compared to viking soils the mixture of materials at the apxs sites is a reflection of the overall complexity of martian surface materials a detailed understanding of which should drive the choice of future instruments and missions

the structural evolution of the western irish variscides an example of obstacle tectonics abstract detailed mesostructural and strain analysis investigations across the killarney mallow fault i e the traditional variscan front in southwest ireland reveal that this structural line separates two distinct tectonic regimes north of the killarney mallow fault bulk shortening orthogonal to orogenic strike is estimated to be 12 all of which is accounted for by late stage buckling microscopic strain analysis reveals that there is only local development of a tectonic fabric south of the front bulk shortening is 40 due to combined layer parallel shortening lps buckling and faulting variscan deformation is presented as being essentially coaxial the regional finite strain pattern outlined above is thought to be primarily controlled by the combined effect of a buried basement obstacle in eastern iveragh and increased sedimentary pile thickness at the western end of the orogen

correlating multispectral imaging and compositional data from the mars exploration rovers and implications for mars science laboratory abstract in an effort to infer compositional information about distant targets based on multispectral imaging data we investigated methods of relating mars exploration rover mer pancam multispectral remote sensing observations to in situ alpha particle x ray spectrometer apxs derived elemental abundances and mossbauer mb derived abundances of fe bearing phases at the mer field sites in gusev crater and meridiani planum the majority of the partial correlation coefficients between these data sets were not statistically significant restricting the targets to those that were abraded by the rock abrasion tool rat led to improved pearson s correlations most notably between the red blue ratio 673 nm 434 nm and fe3 bearing phases but partial correlations were not statistically significant partial least squares pls calculations relating pancam 11 color visible to near ir vnir 400 1000 nm spectra to apxs and mossbauer element or mineral abundances showed generally poor performance although the presence of compositional outliers led to improved pls results for data from meridiani when the meridiani pls model for pyroxene was tested by predicting the pyroxene content of gusev targets the results were poor indicating that the pls models for meridiani are not applicable to data from other sites soft independent modeling of class analogy simca classification of gusev crater data showed mixed results of the 24 gusev test regions of interest rois with known classes 11 had 30 of the pixels in the roi classified correctly while others were mis classified or unclassified k means clustering of apxs and mossbauer data was used to assign meridiani targets to compositional classes the clustering derived classes corresponded to meaningful geologic and or color unit differences and simca classification using these classes was somewhat successful with 30 of pixels correctly classified in 9 of the 11 rois with known classes this work shows that the relationship between swir multispectral imaging data and apxs and mossbauer derived composition mineralogy is often weak a perhaps not entirely unexpected result given the different surface sampling depths of swir imaging uppermost few microns vs apxs tens of m and mb measurements hundreds of m results from the upcoming mars science laboratory msl rover s chemcam laser induced breakdown spectroscopy libs instrument may show a closer relationship to mastcam swir multispectral observations however because the initial laser shots onto a target will analyze only the upper few micrometers of the surface the clustering and classification methods used in this study can be applied to any data set to formalize the definition of classes and identify targets that do not fit in previously defined classes

british columbia flood scars maximum flood stage indicators abstract flood scars abundant along rivers of heavily forested northern british columbia provide records of flood occurrence and magnitude in a region with few and relatively short gaging records log transport during floods is episodic and occurs almost immediately preceding and during peak stage impact wounds form during this transport stage many of these logs are sequestered in bankside vegetation where they form abrasion wounds on trees by rubbing up and down in the turbulent waters from may 30 through june 2 1990 an approximate 9 year nival flood occurred on the skeena river at cedarvale b c this flood damaged many trees within a few tree spacings of the bank margin immediately after the flood the peak stage line along 170 m of shoreline was marked in september 1992 48 flood scarred trees were selected and their locations and flood scar heights surveyed the mean height of the top of the flood scars sampled is 20 3 cm below the peak stage on the adjacent bank flood scar heights range from 9 to 80 cm compared to the peak stage on the adjacent bank a regression line for the floodscar top elevations is roughly parallel to the peak stage elevations along the shoreline and approximately 20 cm below it data from usk the nearest gaging station on the skeena river demonstrate that the stage was high enough to form the flood scars for only 24 to 36 hours most of the flood scars had to form in less than 24 hours field observations suggest that the time of flood scar formation was even more restricted

flexural shear in a periclinal fold from the irish variscides abstract periclinal folds occur in a structural culmination in the centre of the irish variscan fold belt the culmination marks a zone of enhanced shortening which is associated with a locally attenuated stratigraphy and an anomalous deformation sequence with respect to the remainder of the orogen originally vertical burrows have been used along with cleavage fold relations to study both the three dimensional evolution of the periclinal folding and the temporal relationship between folding and cleavage as well as cleavage forming flattening strains the burrows record along strike shear related to the propagation of the periclinal folds a comparison with strain measurements made outside the culmination zone shows that the galley head area suffered higher strains integration of field data with published analyses of plasticine modelling of periclinal folds yields models for the propagation of a pericline and for the geometry of its lateral terminations

the mvacs surface stereo imager on mars polar lander the surface stereo imager ssi a stereoscopic multispectral camera on the mars polar lander is described in terms of its capabilities for studying the martian polar 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 13 8 high by 14 3 wide and has 12 selectable filters between 440 and 1000 nm the 18 optics have a large depth of field and no focusing mechanism is required a mechanical shutter is avoided by using the frame transfer capability of the 528 512 ccd the resolving power of the camera 0 975 mrad pixel is the same as the imager for mars pathfinder camera of which it is nearly an exact copy specially designed targets are positioned on the lander they provide information on the magnetic properties of windblown dust and radiometric standards for calibration several experiments beyond the requisite color panorama are described in detail contour mapping of the local terrain multispectral imaging of interesting features possibly with ice or frost in shaded spots to study local mineralogy and atmospheric imaging to constrain the properties of the haze and clouds eight low transmission filters are included for imaging the sun directly at multiple wavelengths to give ssi the ability to measure dust opacity and potentially the water vapor content this paper is intended to document the functionality and calibration of the ssi as flown on the failed lander

aeolian features and processes at the mars pathfinder landing site the mars pathfinder landing site contains abundant features attributed to aeolian or wind processes these include wind tails drift deposits duneforms of various types ripplelike features and ventifacts the first clearly seen on mars many of these features are consistant with formation involving sand size particles although some features such as dunes could develop from saltating sand size aggregates of finer grains the discovery of ventifact flutes cut in rocks strongly suggests that at least some of the grains are crystalline rather than aggregates excluding the ventifacts the orientations of the wind related features correlate well with the orientations of bright wind steaks seen on viking orbiter images in the general area they also correlate with wind direction predictions from the nasa ames general circulation model gcm which show that the strongest winds in the area occur in the northern hemisphere winter and are directed toward 209

the color of mars spectrophotometric measurements at the pathfinder landing site we calculate the color of the martian sky and surface directly using the absolute calibration of the mars pathfinder mpf lander camera which was observed to be stable during the mission the measured colors of the martian sky and surface at the pathfinder site are identical to the viking sites i e a predominantly yellowish brown color with only subtle variations these colors are distributed continuously and fall into five overlapping groups with distinct average colors and unique spatial characteristics shadowed soil soil soil rock mixtures rock and sky we report that the primary difference between the sky color and the color of the rocks is due to a difference in brightness measurements of the sky color show that the sky reddens away from the sun and toward the horizon and that the sky color varies with time of day and is reddest at local noon we present a true color picture of the martian surface and color enhancement techniques that increase image saturation maximize color discriminability while preserving hue and eliminate brightness variations while preserving the chromaticity of the scene although mars has long been called the red planet quantitative measurements of the surface color from telescopic and surface observations indicate a light to moderate yellowish brown color the pathfinder camera measurements presented here support the claim that the red planet is not red but indeed yellowish brown

examining the sediments and soils of gusev crater with the athena science payload 1 gusev crater has been proposed to contain lacustrine and or fluvial sediments however eolian or volcanic sediments global dust and locally produced soils may also be present this work describes the use of the athena instrument package to evaluate the environment in which sampled materials were deposited in gusev crater sedimentary or soil deposits can be sampled by examining materials that were 1 excavated by impact events 2 revealed by wind deflation or 3 exposed by spinning the rover wheels specific observations can be diagnostic of a depositional environment for instance pancam images of thin e g 5 cm planar layers of phyllosilicates and or evaporites as determined by mini tes would suggest lacustrine sediments layered sediments e g trough cross bed with rounded particles 4 mm would suggest fluvial activity eolian sediments may have planar or cross planar layers of well sorted grains 200 m parallel bed deposits consisting of glass observable by microscopic imager would indicate volcanic ash soil bulk chemistry reported by alpha particle x ray spectrometer that is similar to the viking and mars pathfinder soils would indicate global dust mini tes should only detect primary mineralogies in physically weathered soils whereas chemically weathered soils may contain carbonates sulfates and or phyllosilicates although some characteristics are unique to a sediment or soil deposit different deposit types can have similar characteristics e g planar layering determining the depositional history of material in gusev will require the integration of measurements from several instruments and careful geologic reasoning by the investigators

mars exploration rover engineering cameras 1 nasa s mars exploration rover mer mission will place a total of 20 cameras 10 per rover onto the surface of mars in early 2004 fourteen of the 20 cameras are designated as engineering cameras and will support the operation of the vehicles on the martian surface images returned from the engineering cameras will also be of significant importance to the scientific community for investigative studies of rock and soil morphology the navigation cameras navcams two per rover are a mast mounted stereo pair each with a 45 square field of view fov and an angular resolution of 0 82 milliradians per pixel mrad pixel the hazard avoidance cameras hazcams four per rover are a body mounted front and rear facing set of stereo pairs each with a 124 square fov and an angular resolution of 2 1 mrad pixel the descent camera one per rover mounted to the lander has a 45 square fov and will return images with spatial resolutions of 4 m pixel all of the engineering cameras utilize broadband visible filters and 1024 1024 pixel detectors

overview of the magnetic properties experiments on the mars exploration rovers 1 the mars exploration rovers have accumulated airborne dust on different types of permanent magnets images of these magnets document the dynamics of dust capture and removal over time the strongly magnetic subset of airborne dust appears dark brown to black in panoramic camera pancam images while the weakly magnetic one is bright red images returned by the microscopic imager reveal the formation of magnetic chains diagnostic of magnetite rich grains with substantial magnetization 8 am2 kg 1 on the basis of mossbauer spectra the dust contains magnetite olivine pyroxene and nanophase oxides in varying proportions depending on wind regime and landing site the dust contains a larger amount of ferric iron fe3 fetot 0 6 than rocks in the gusev plains 0 1 0 2 or average gusev soil 0 3 alpha particle x ray spectrometer data of the dust show that some of the iron in magnetite is substituted by titanium and chromium the good correlation of the amount of calcium and sulfur in the dust may be caused by the presence of a calcium sulfate related phase the overall mineralogical composition points to a basaltic origin of the airborne dust although some alteration has taken place as indicated by the large degree of oxidation

quantitative morphology of rocks at the mars pathfinder landing site 1 we adapt and test a standard terrestrial technique of assessing morphology quantitatively for use with sites on mars based on two dimensional equations and particle outlines whereby images of particles obtained remotely may yield dimensionless numerical shape and roundness values consistent with previous knowledge of the lithology and sedimentary transport history our test site was the particle rich rock garden at the mars pathfinder landing site a location where the primary geologic processes and lithology have been determined by other means a total of 575 particles were assessed in terms of size sphericity elongation and roundness qualitative roundness was determined for 460 particles particles are mostly pebble to cobble sized and have an average sphericity of 0 75 elongation of 0 63 and relative roundness of 0 083 69 of particles are subangular or subrounded particle sphericity is unimodal with a size sphericity profile matching trends for terrestrial populations of similar lithology and elongations nearly identical to those for particles at vikings 1 and 2 this matches the predictions for a site with the single overall lithology implied from other analyses roundness data indicate one or possibly two particle populations representing the primary processes that likely affected particle roundness most strongly impact and catastrophic flooding finally we tested a hypothesis suggesting that darker smaller more angular particles comprise a population transported through impact cratering while larger less dark more rounded particles are associated with catastrophic flood transport the opposite result is seen larger particles throughout the rock garden are more angular than smaller ones

results of the imager for mars pathfinder windsock experiment the imager for mars pathfinder imp windsock experiment measured wind speeds at three heights within 1 2 m of the martian surface during pathfinder landed operations these wind data allowed direct measurement of near surface wind profiles on mars for the first time including determination of aerodynamic roughness length and wind friction speeds winds were light during periods of windsock imaging but data from the strongest breezes indicate aerodynamic roughness length of 3 cm at the landing site with wind friction speeds reaching 1 m s maximum wind friction speeds were about half of the threshold of motion friction speeds predicted for loose fine grained materials on smooth martian terrain and about one third of the threshold of motion friction speeds predicted for the same size particles over terrain with aerodynamic roughness of 3 cm consistent with this and suggesting that low wind speeds prevailed when the windsock array was not imaged and or no particles were available for aeolian transport no wind related changes to the surface during mission operations have been recognized the aerodynamic roughness length reported here implies that proposed deflation of fine particles around the landing site or activation of duneforms seen by imp and sojourner would require wind speeds 28 m s at the pathfinder top windsock height or 31 m s at the equivalent viking wind sensor height of 1 6 m and wind speeds 45 m s above 10 m these wind speeds would cause rock abrasion if a supply of durable particles were available for saltation previous analyses indicate that the pathfinder landing site probably is rockier and rougher than many other plains units on mars so aerodynamic roughness length elsewhere probably is less than the 3 cm value reported for the pathfinder site

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

diachronous and independent histories of plutonism and mineralization in the cornubian batholith southwest england concordant u pb dates of magmatic monazites in the dominant coarse grained biotite muscovite granites of the late variscan cornubian batholith demonstrate that the emplacement of the six main plutons was diachronous ranging from 293 1 1 3 ma carnmenellis to 274 5 1 4 ma land9s end southern lobe 40 ar 39 ar age spectra for magmatic muscovites confirm that cooling to about 320 c at the present level of exposure was accomplished within 4 to 5 ma in each intrusion moreover age spectra for hydrothermal muscovites show that development of the major sn cu lodes of the south crofty mine commenced before 286 ma only 2 to 3 ma after cooling of the hosting cam brea granite a satellite of the carnmenellis pluton the older plutons had therefore approached ambient temperatures and had even experienced intense hydrothermal activity before emplacement of the youngest

mars exploration rover athena panoramic camera pancam investigation 1 the panoramic camera pancam investigation is part of the athena science payload launched to mars in 2003 on nasa s twin mars exploration rover mer missions the scientific goals of the pancam investigation are to assess the high resolution morphology topography and geologic context of each mer landing site to obtain color images to constrain the mineralogic photometric and physical properties of surface materials and to determine dust and aerosol opacity and physical properties from direct imaging of the sun and sky pancam also provides mission support measurements for the rovers including sun finding for rover navigation hazard identification and digital terrain modeling to help guide long term rover traverse decisions high resolution imaging to help guide the selection of in situ sampling targets and acquisition of education and public outreach products the pancam optical mechanical and electronics design were optimized to achieve these science and mission support goals pancam is a multispectral stereoscopic panoramic imaging system consisting of two digital cameras mounted on a mast 1 5 m above the martian surface the mast allows pancam to image the full 360 in azimuth and 90 in elevation each pancam camera utilizes a 1024 1024 active imaging area frame transfer ccd detector array the pancam optics have an effective focal length of 43 mm and a focal ratio of f 20 yielding an instantaneous field of view of 0 27 mrad pixel and a field of view of 16 16 each rover s two pancam eyes are separated by 30 cm and have a 1 toe in to provide adequate stereo parallax each eye also includes a small eight position filter wheel to allow surface mineralogic studies multispectral sky imaging and direct sun imaging in the 400 1100 nm wavelength region pancam was designed and calibrated to operate within specifications on mars at temperatures from 55 to 5 c an onboard calibration target and fiducial marks provide the capability to validate the radiometric and geometric calibration on mars

the nanophase iron mineral s in mars soil a series of surface modified clays containing nanophase np iron oxide oxyhydroxides of extremely small particle sizes with total iron contents as high as found in mars soil were prepared by iron deposition on the clay surface from ferrous chloride solution comprehensive studies of the iron mineralogy in these mars soil analogs were conducted using chemical extractions solubility analyses ph and redox x ray and electron diffractometry electron microscopic imaging specific surface area and particle size determinations differential thermal analyses magnetic properties characterization spectral reflectance and viking biology simulation experiments the clay matrix and the procedure used for synthesis produced nanophase iron oxides containing a certain proportion of divalent iron which slowly converts to more stable fully oxidized iron minerals the clay acted as an effective matrix both chemically and sterically preventing the major part of the synthesized iron oxides from ripening i e growing and developing larger crystals the precipitated iron oxides appear as isodiametric or slightly elongated particles in the size range 1 10 nm having large specific surface area the noncrystalline nature of the iron compounds precipitated on the surface of the clay was verified by their complete extractability in oxalate lepidocrocite gamma feooh was detected by selected area electron diffraction it is formed from a double iron fe ii fe iii hydroxy mineral such as green rust or ferrosic hydroxide magnetic measurements suggested that lepidocrocite converted to the more stable maghemite gamma fe2o3 by mild heat treatment and then to nanophase hematite alpha fe2o3 by extensive heat treatment after mild heating the iron enriched clay became slightly magnetic to the extent that it adheres to a hand held magnet as was observed with mars soil the chemical reactivity of the iron enriched clays strongly resembles and offers a plausible mechanism for the somewhat puzzling observations of the viking biology experiments their unique chemical reactivities are attributed to the combined catalytic effects of the iron oxide oxyhydroxides and silicate phase surfaces the reflectance spectrum of the clay iron preparations in the visible range is generally similar to the reflectance curves of bright regions on mars this strengthens the evidence for the predominance of nanophase iron oxides oxyhydroxides in mars soil the mode of formation of these nanophase iron oxides on mars is still unknown it is puzzling that despite the long period of time since aqueous weathering took place on mars they have not developed from their transitory stage to well crystallized end members the possibility is suggested that these phases represent a continuously on going extremely slow weathering process

mineralogy composition and alteration of mars pathfinder rocks and soils evidence from multispectral elemental and magnetic data on terrestrial analogue snc meteorite and pathfinder samples major element multispectral and magnetic properties data were obtained at ares vallis during the mars pathfinder mission to understand the compositional mineralogical and process implications of these data we obtained major element mineralogical and magnetic data for well crystalline and nanophase ferric minerals terrestrial analogue samples with known geologic context and snc meteorites analogue samples include unaltered palagonitic and sulfatetic tephra from mauna kea volcano hydrolytic and acid sulfate alteration steam vent material from kilauea volcano hydrolytic alteration and impactites from meteor crater relithification salient results for mars pathfinder include 1 band depths bd530b and bd600 and the reflectivity ratio r800 r750 are consistent with the dominant ferric mineral being nanophase ferric oxide associated with an unknown amount of h2o and occurring in composite particles along with subordinate amounts of other ferric minerals hematite and hematite plus nanophase goethite are most consistent with the data but maghemite akaganeite schwertmannite and nanophase lepidocrocite are also possible interpretations ferric oxides that are consistently not favored by the data as sole alteration products are jarosites and well crystalline goethite and lepidocrocite 2 the strength of the ferric adsorption edge r750 r445 implies the fe3 fe2 values for pathfinder rock and soil are within the ranges 0 7 3 and 3 20 respectively 3 ferrous silicates are indicated for subsets of pathfinder rocks and soils one subset has a band minimum near 930 nm that can attributed to low ca pyroxene alternatively the band could be a second manifestation of certain ferric oxides including nanophase goethite maghemite akaganeite and schwertmannite another subset has a negative spectral slope from 800 to 1005 nm which could result from the high energy wing of a high ca pyroxene and or olivine band a mixture of bright and dark materials and for rocks thin coatings of bright dust on dark rocks 4 chemical data on pathfinder rocks and soils are consistent with two component mixtures between an andesitic rock with low mgo and so3 concentrations soil free rock and a global basaltic soil with high mgo and so3 concentrations rock free soil pathfinder rock free soil can be modeled as a chemical mixture of snc meteorites and the pathfinder soil free rock 5 pathfinder soil cannot be obtained by chemical alteration of pathfinder rocks by any of the hydrolytic and acid sulfate alteration processes we studied presumably global mixing has obscured and possibly erased the elemental signatures of chemical alteration 6 the strongly magnetic phase in palagonitic and sulfatetic tephra is titanomagnetite and possibly its oxidation product titanomaghemite fe ti spinels the saturation magnetization of the tephra samples 0 5 2 0 am2 kg is at or below the low end of the range inferred for martian dust 4 2 am2 kg implying that lithogenic fe ti spinels are a possible candidate for the martian strongly magnetic phase 7 the predominantly palagonitic spectral signature and magnetic nature of martian soil and dust are consistent with glassy precursors with imbedded fe ti spinel particles comparison with lunar glass production rates suggests that production of sufficient quantities of glassy materials on mars by volcanic and impact processes is sufficient to account for these observations

mineralogic and compositional properties of martian soil and dust results from mars pathfinder mars pathfinder obtained multispectral elemental magnetic and physical measurements of soil and dust at the sagan memorial station during the course of its 83 sol mission we describe initial results from these measurements concentrating on multispectral and elemental data and use these data along with previous viking snc meteorite and telescopic results to help constrain the origin and evolution of martian soil and dust we find that soils and dust can be divided into at least eight distinct spectral units based on parameterization of imager for mars pathfinder imp 400 to 1000 nm multispectral images the most distinctive spectral parameters for soils and dust are the reflectivity in the red the red blue reflectivity ratio the near ir spectral slope and the strength of the 800 to 1000 nm absorption feature most of the pathfinder spectra are consistent with the presence of poorly crystalline or nanophase ferric oxide s sometimes mixed with small but varying degrees of well crystalline ferric and ferrous phases darker soil units appear to be coarser grained compacted and or mixed with a larger amount of dark ferrous materials relative to bright soils nanophase goethite akaganeite schwertmannite and maghemite are leading candidates for the origin of the absorption centered near 900 nm in imp spectra the ferrous component in the soil cannot be well constrained based on imp data alpha proton x ray spectrometer apxs measurements of six soil units show little variability within the landing site and show remarkable overall similarity to the average viking derived soil elemental composition differences exist between viking and pathfinder soils however including significantly higher s and cl abundances and lower si abundances in viking soils and the lack of a correlation between ti and fe in pathfinder soils no significant linear correlations were observed between imp spectral properties and apxs elemental chemistry attempts at constraining the mineralogy of soils and dust using normative calculations involving mixtures of smectites and silicate and oxide minerals did not yield physically acceptable solutions we attempted to use the pathfinder results to constrain a number of putative soil and dust formation scenarios including palagonitization and acid fog weathering while the pathfinder soils cannot be chemically linked to the pathfinder rocks by palagonitization this study and mcsween et al 1999 suggest that palagonitic alteration of a martian basaltic rock plus mixture with a minor component of locally derived andesitic rock fragments could be consistent with the observed soil apxs and imp properties

surface geology from viking landers on mars a second look aside from reddish dust products of martian weathering are not abundantly obvious on viking lander images surface stones appear sound spalls and disintegration fragments are largely lacking pitting of stones is probably not due to differential weathering and reddish stone colors more likely result from adhered dust than from patination judging from wind scoured drifts deflated ground rippled bed forms lee side tails basal scours fretted rocks and ubiquitous dust wind is currently the most effective transportive and erosive agent the dogma that martian eolian material is almost exclusively of 10 100 size is challenged by granule ripples and the possibility that wind drifted deposits consist largely of sand sized particles fretting is more common than faceting on martian ventifacts crusts on martian surface fines are more akin to case hardened rinds than to true duricrust crusting a possibly continuing process may be the product of atmospheric breathing of the regolith pits on surfaces of many martian stones are probably vesicles modified by eolian erosion pits on nonvesicular rocks may be solely the product of wind blasting vesicular lava dense lava and breccias are the most likely rocks among surface stones around the landers the bedrock outcrops near vl 1 may be large boulders embedded in a breccia substrate pyroclastics seem a likely constituent of surface deposits

snc meteorites clues to martian petrologic evolution the shergottites nakhlites and chassigny snc meteorites are apparently cumulate mafic and ultramafic rocks that crystallized at shallow levels in the crust of their parent body the mineralogy and chemistry of these meteorites are remarkably like equivalent terrestrial rocks although their ratios of fe fe mg and certain incompatible elements and their oxygen isotopic compositions are distinctive all have crystallization ages of 1 3 b y or younger and formed from magmas produced by partial melting of previously fractionated source regions isotope systematics suggest that the snc parent body had a complex and protracted thermal history spanning most of geologic time some meteorites have been severely shock metamorphosed and all were ejected from their parent body at relatively recent times possibly in several impact events late crystallization ages complex petrogenesis and possible evidence for a large gravitational field suggest that these meteorites are derived from a large planet trapped gases in shergottite shock melts have compositions similar to the composition measured in the martian atmosphere ejection of martian meteorites may have been accomplished by acceleration of near surface spalls or other mechanisms not fully understood if snc meteorites are of martian origin they provide important information on planetary composition and evolution the bulk composition and redox state of the martian mantle as constrained by shergottite phase equilibria must be more earthlike than most current models planetary thermal models should benefit from data on the abundances of radioactive heat sources the melting behavior of the mantle and the timing of planetary differentiation calculated depletion of chalcophile elements in source regions indicates a core dominated by sulfides and paleomagnetic measurements suggest the presence of a weak magnetic field within the last several hundred thousand years concentrations of volatile elements indicate that the snc parent body was not volatile depleted and trapped atmospheric components measured in shock melts may be useful in understanding planetary degassing by providing comparisons for spectral reflectance data and viking soil analyses these meteorites may also constrain surface mineralogy and weathering mechanisms

evidence for martian electrostatic charging and abrasive wheel wear from the wheel abrasion experiment on the pathfinder sojourner rover the wheel abrasion experiment wae on the mars pathfinder rover was designed to find out how abrasive the martian dust would be on strips of pure metals attached to one of the wheels a specially modified wheel with 15 thin film samples five each of three different metals specularly reflected sunlight to a photovoltaic sensor when the wheel was rotated to present the different sample surfaces to the sensor the resulting signal was interpreted in terms of dust adhesion and abrasive wear many data sequences were obtained ground tests of similar wheels in a simulated martian environment showed that static charging levels of 100 300 v could be expected to prevent the possibility of paschen discharge in the low pressure martian atmosphere charge dissipation points were added to the sojourner rover and were shown in ground tests to keep charging levels at 80 v or less nevertheless significant dust accumulations on sojourner s wheels may be interpreted as evidence for electrostatic charging simple considerations of the expected maximum level of charging and electrostatic dust adhesion lead to an estimate for the size of the adhering dust grains from the wae data it is hypothesized that the photoelectric effect is the most important mechanism for slow discharge in martian daylight sensor signals obtained late in the pathfinder mission show that significant wheel wear was seen on the metal wheel strips with the most wear on the thinnest aluminum samples and the least on the thickest nickel and platinum samples an estimate is made of the reflectance of the adhering martian dust the depth of dig of the wae wheel shows that the dust is in some places very loose and in others tightly packed finally comparison of the wae results with ground test results makes possible a comparison of the martian soil with mineral grain types and sizes found on earth and show that the martian dust is fine grained and of limited hardness