searching at the right time of day evidence for aqueous minerals in columbus crater with tes and themis data the primary objective of the thermal emission imaging system themis experiment which has been in orbit at mars since early 2002 is to identify minerals associated with hydrothermal and subaqueous environments data from themis have supported the presence of clays silica rich deposits and chlorides but has not before provided definitive evidence for the presence of sulfates this is an especially puzzling result given that sulfates have been extensively identified with other instruments at mars if present sufficiently exposed and in high enough abundances such minerals should be detectable in orbital thermal infrared spectra at the resolution of themis the extended mission proposal for themis on mars odyssey suggests that the detection of all minerals may be enhanced by observing at an earlier time of day and thus at warmer temperatures therefore in 2009 odyssey moved to an earlier orbit time here we examine themis data collected when the earlier orbit time coincided with the martian local southern late summer ls 270 for columbus crater where compact reconnaissance imaging spectrometer for mars crism data have detected a number of aqueous minerals some of the warmest themis images show evidence for aqueous minerals although not in the same locations where crism finds the highest concentrations several factors contribute to this result including differences in the diurnal temperature curve and levels of induration and particle size for themis earlier time of day and proper seasonal observations combine to provide warm surface temperatures and ideal low atmospheric opacity that significantly increases the ability to definitively identify low spectral contrast aqueous minerals at the surface of mars

the stokes drift and wave induced mass flux in the north pacific 1 stokes drift and wave induced mass flux in realistic wavefields and ocean currents in the north pacific ocean are studied using a third generation wave model with ambient geostrophic currents estimated from satellite altimetry data to directly estimate the stokes drift for random directional waves comparison with in situ buoy data shows that the model performed well in representing the stokes drift field and total wave momentum in the north pacific the annual mean surface stokes drift ranges from 2 to 10 cm s and the mean stokes e folding depth is 1 to 2 m the stokes drift fields estimated using bulk wave parameters compare poorly against buoy data and are shown to overestimate underestimate the stokes e folding depth the surface stokes drift computed directly from wave spectra by as much as 5 20 times larger 2 10 times smaller the spatial distributions of mean wave height and mass transport approximately follow the synoptic scale associated with atmospheric forcing and the divergence of wave induced mass flux is significantly modified by local fetch the coast and ocean currents due to strong wave refraction along the kuroshio extension surface vertical velocity induced by stokes divergence is comparable to the ekman velocity and may alter the meso scale dynamics of the front

a global view of martian surface compositions from mgs tes thermal emission spectrometer tes data from the mars global surveyor mgs are used to determine compositions and distributions of martian low albedo regions two surface spectral signatures are identified from low albedo regions comparisons with spectra of terrestrial rock samples and deconvolution results indicate that the two compositions are a basaltic composition dominated by plagioclase feldspar and clinopyroxene and an andesitic composition dominated by plagioclase feldspar and volcanic glass the distribution of the two compositions is split roughly along the planetary dichotomy the basaltic composition is confined to older surfaces and the more silicic composition is concentrated in the younger northern plains

compositional heterogeneity of the ancient martian crust analysis of ares vallis bedrock with themis and tes data 1 themis multispectral and thermophysical information combined with tes hyperspectral and albedo data is used as a powerful high spectral spatial resolution tool to investigate the mineralogic heterogeneity of ancient martian crust exposed in ares vallis bedrock three major spectral units are present in the upper ares vallis region 1 a regional unit that is composed primarily of a high silica si o 0 35 component with lesser amounts of plagioclase and pyroxene and is associated with channel wall rock and surrounding plains 2 a pyroxene and olivine rich rock unit exposed as a 250 m thick contiguous layer in the wall rock of ares vallis as well as in isolated exposures in the plains outside of the channel and 3 a unit composed of plagioclase pyroxene and lesser high silica component s si o 0 35 that primarily occurs as low albedo sand the spatial and stratigraphic distribution of these units suggests that the pyroxene and olivine enriched unit may be extrusive and or intrusive in origin indicating that this region experienced either a single stage or repeated episodes of olivine enriched magmatism during the first 1 5 gyr of crust formation this olivine enrichment may have been caused by a larger degree of mantle partial melting facilitated by higher mantle temperature melting from a more depleted mantle source and or less olivine fractionation relative to regional rock parent magmas the olivine rich unit is similar in thermophysical character to previously published olivine bearing terrains on mars but the derived modal mineralogy consists of 20 more pyroxene and less plagioclase than those terrains

rock spectral classes observed by the spirit rover s pancam on the gusev crater plains and in the columbia hills 1 this paper examines the ferrous and ferric iron mineralogy of rocks inferred from 246 visible near infrared 430 1010 nm multispectral observations made by the mars exploration rover spirit s pancam on its traverse from its landing site to its second winter haven location principal component correspondence analyses and a sequential maximum angle convex cone technique were used to identify 14 candidate classes spectra from the west spur of husband hill and the watchtower area had the highest 535 and 601 nm band depths indicating that these areas were more oxidized differences in the depth and band center of a near infrared nir absorption feature were observed using 904 nm band depth and 803 904 nm ratio and parameters gauging the 754 864 and 754 1009 nm slopes spectra of rocks from the southern flank of husband hill had negative 754 1009 nm slopes and a broad nir absorption consistent with high olivine abundances rocks observed on the lower west spur at the cumberland ridge locale at the husband hill summit and at the haskin ridge locale had deep 904 nm band depths and steep 754 864 nm slopes consistent with greater pyroxene abundances these observations are consistent with results on iron bearing mineralogy from spirit s mossbauer spectrometer comparisons of these rock spectral classes with a set of terrestrial analog samples found similarities between the west spur and watchtower classes and red hematite bearing impact melts fewer similarities were found in comparisons of the columbia hills classes with basaltic hydrovolcanic tephras

characterization of hydrated silicate bearing outcrops in tyrrhena terra mars implications to the alteration history of mars abstract the tyrrhena terra region of mars is studied with the imaging spectrometers omega observatoire pour la mineralogie l eau les glaces et l activite onboard mars express and crism compact reconnaissance infrared spectrometer for mars onboard mars reconnaissance orbiter through the observation of tens of craters that impacted into this part of the martian highlands the 175 detections of hydrated silicates are reported mainly associated with ejecta blankets crater walls and rims and central up lifts sizes of craters where hydrated silicates are detected are highly variable diameters range from less than 1 km to 42 km we report the presence of zeolites and phyllosilicates like prehnite mg chlorite mg rich smectites and mixed layer chlorites smectites and chlorite vermiculite from comparison of hyperspectral infrared observations with laboratory spectra these minerals are associated with fresh craters post dating any aqueous activity they likely represent ancient hydrated terrains excavated by the crater forming impacts and hence reveal the composition of the altered noachian crust although crater related hydrothermal activity may have played a minor role for the largest craters 20 km in diameter most detected minerals formed over relatively high temperatures 100 300 c likely due to aqueous alteration of the noachian crust by regional low grade metamorphism from the noachian thermal gradient and or by extended hydrothermal systems associated with noachian volcanism and ancient large impact craters this is in contrast with some other phyllosilicate bearing regions like mawrth vallis where smectites kaolinites and hydrated silica were mainly identified pointing to a predominance of surface shallow sub surface alteration and where excavation by impacts played only a minor role smooth plains containing hydrated silicates are observed at the boundary between the noachian altered crust dissected by fluvial valleys and the hesperian unaltered volcanic plains these plains may correspond to alluvial deposition of eroded material the highlands of tyrrhena terra are therefore particularly well suited for investigating the diversity of hydrated minerals in ancient martian terrains

evidence for noachian flood volcanism in noachis terra mars and the possible role of hellas impact basin tectonics 1 spectral and imaging data sets from mars reconnaissance orbiter and mars odyssey as well as spectral and topographic data from mars global surveyor are used to understand the origin of in place rock units found in the intercrater plains and hellas circumferential graben floors of noachis terra mars the rocky units are interpreted as effusive volcanic plains on the basis of broad areal extent structural competence association with topographic lows distinct mineralogy from regolith and lack of sedimentary textures or minerals associated with aqueous processes some rocky expanses contain at least two compositionally distinct units the relatively light toned unit exhibits a higher plagioclase pyroxene ratio than the lower dark toned unit both units exhibit 10 olivine enrichment compared to surrounding regolith these units are heavily degraded and exhibit crater model ages between 3 80 and 4 0 ga making these some of the oldest preserved volcanic plains accessible by remote sensing they are found in association with hellas ring structures where the westward extent of these rocky units is limited to the outermost ring structure fracturing associated with the hellas impact may have enabled magmas to ascend from the base of the crust in the circum hellas region identification of these units as volcanic materials extends previous estimates for volume of outgassed volatiles though the estimated volcanic volume increase is minor the local effects could have been significant the role of multi ring impact basins in providing a spatial control on martian highlands volcanism and subsurface mineralization may have been underestimated in the past

regional scale stratigraphy of surface units in tyrrhena and iapygia terrae mars insights into highland crustal evolution and alteration history 1 the compositional thermophysical and geologic characteristics of surface units in iapygia and tyrrhena terra 60 e 100 e 0 30 s provide new insights into the compositional stratigraphy of the region intercrater plains are dominated by two surface units the older unit unit 1 is deficient in olivine and more degraded and likely consists of a mixture of impact volcanic and sedimentary materials the younger unit unit 2 is enriched in olivine exhibits a resistant morphology and higher thermal inertia and likely represents volcanic infilling of plains units 1 and 2 bear a strong resemblance to those previously mapped in mare serpentis a section of highlands crust located northwest of hellas basin thus the two major intercrater plains units are even more widespread than previously thought and therefore likely constitute important components of mars highland stratigraphy many craters in the region contain high thermal inertia deposits unit 3 that are compositionally identical to unit 2 these may have formed via volcanic infilling or may represent sedimentary materials that have been eroded from crater walls and lithified less common units include olivine and or pyroxene rich massifs and crater central peaks these are primarily found within hellas basin rim units and may represent mantle materials brought toward the surface during the hellas impact putative chloride deposits are primarily associated with olivine deficient surfaces unit 1 that may be heavily degraded occurrences of unit 2 the observations raise a variety of questions related to martian crustal evolution and alteration that may have more widespread implications outside the study region

identification of quartzofeldspathic materials on mars 1 a unique spectral component has been identified near and on the central peaks of two 30 km diameter craters in northern syrtis major these exposures are clearly visible in thermal emission imaging system themis color radiance images as well as themis and thermal emission spectrometer tes surface emissivity data both tes and themis data indicate the presence of increased 1050 1250 cm 1 8 9 5 m absorption compared to the surrounding basaltic plains and tes data also display other absorptions at 400 470 and 800 cm 1 25 20 and 12 m consistent with the presence of quartz ratio and isolated central peak spectral unit spectra match laboratory emissivity spectra of granitoid rocks composed primarily of quartz and plagioclase feldspar deconvolution results also indicate that the surface contains quartz and feldspar in addition to a high si glass and or sheet silicate component because central peak materials are brought up from depth during the cratering event the association of the quartzofeldspathic mineralogy with the central peaks of the craters indicates that the quartz bearing material was excavated from depth the occurrence in the two adjacent craters may imply a granitoid pluton of considerable extent a plausible formation mechanism for this relatively silicic material may be similar to that of terrestrial trondhjemites which do not require plate tectonics the rarity of the exposures implies that the process that formed the granitoid composition was probably not widespread the presence of quartz bearing material on mars indicates that mechanisms that produce highly differentiated magmas have been present and extends the diversity of surface compositions identified

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

variations in martian surface composition and cloud occurrence determined from thermal infrared spectroscopy analysis of viking and mariner 9 data viking infrared thermal mapper irtm and mariner 9 infrared interferometer spectrometer iris data were examined for evidence of spatial variations in the composition of surface materials and the abundance of atmospheric condensates the irtm instrument collected broadband spectral radiance in bands centered at 7 9 11 and 20 m these measurements were converted to emissivities at 9 11 and 20 m and used to construct multispectral images at five seasons ls 90 180 180 360 0 90 90 180 and 180 360 and at local times of 6 8 8 10 10 12 12 14 and 14 16 h 24 h equals one martian day during dusty periods ls 180 360 these images clearly revealed the presence of suspended dust during clear periods ls 0 180 the seasonal and diurnal variations in water ice cloud occurrence could be mapped using the 11 m irtm band clouds tended to occur over the tharsis region and the region between 0 and 60 w near the equator and to evolve from dispersed hazes to more localized hazes during the day as northern summer progressed during the viking period the northern clouds transitioned from a diffuse haze to a more concentrated zone of clouds in the equatorial region with a well defined northern boundary during clear periods the irtm multispectral data reveal significant absorptions at 9 11 and 20 m that are strongly correlated with surface albedo these absorptions are produced by surface materials and individual four point spectra show compositional variations within both dark and bright material types the iris instrument collected high spectral resolution 2 4 cm 1 data from 6 to 50 m unfortunately only 85 daytime spectra out of the 21 000 total collected were acquired after the intense global dust storm of 1971 subsided after ls 330 the close agreement of these spectra convolved to irtm resolution with the irtm surface spectra confirms that they also represent surface rather than atmospheric materials the irtm four point spectra show similarities with plagioclase feldspar minerals clays and pyroxenes although the low spectral resolution of irtm prevents definitive mineral identification carbonates do not compose a significant fraction of the dark region materials the iris surface spectra show similarities with feldspars clays and pyroxenes in the 8 12 m region but do not match any of these minerals well in the 18 25 m region overall the irtm and iris data are consistent with previous suggestions of mafic to ultramafic compositions but data provide stronger evidence that unweathered plagioclase feldspars may be significant components of the present surface together the irtm and iris reveal the presence of absorption features associated with surface materials which should permit detailed surface compositional mapping using future thermal ir spectral measurements

volcanism on mars more than 15 years of planetary exploration of mars have given insight into the geologic processes that have shaped its surface the newly acquired viking data have shown that volcanism is one of the most important geologic processes operating on mars throughout its history in situ chemical analyses of martian soil by the viking lander spacecraft indicate mafic to ultramafic source rocks this is consistent both with available remote sensing data which indicate the presence of mafic minerals such as pyroxene and olivine and with petrologic modeling based on available geophysical data which suggest that martian lavas are probably iron rich and ultramafic these data strongly suggest that basaltic volcanism is widespread on mars and much of the photogeological data may be studied in this context photogeological analysis of the martian surface has shown two main types of volcanic morphologies the first type is central volcanoes which are volcanic landforms developed by continued and prolonged eruption from a point source vent this category includes 1 shields the classic low profile volcanic mountains of which olympus mons is the most spectacular example 2 domes steep sided constructs such as tharsis tholus that may represent lower rates of eruption than the shields or possibly more silicic lava compositions 3 highland patera radially textured low profile volcanoes that occur in the cratered terrain and are interpreted as ash shields 4 alba patera an apparently unique volcanic landform consisting of a vast volcanic center over 1500 km across with flank slopes of less than a tenth of a degree and 5 various small features such as cinder cones the second major category is volcanic plains which are units recognized by several criteria of which the presence of mare ridges and flow lobes are the most useful volcanic plains are subdivided into four main groups 1 simple flows broad smooth to rolling plains that contain numerous mare type ridges but no flow lobes interpreted as being composed of thick single cooling units 2 complex flows displaying multiple overlapping flow lobes interpreted to be indicative of thin multiple cooling units 3 undifierentiated flows plains that typically lack any morphologic identifying feature but are considered to be volcanic partly on the basis of their association with large volcanic centers and 4 questionable plains volcanic units heavily modified by other processes erosion tectonism etc so that their origins are uncertain when these categories of volcanic morphologies are combined with relative age data provided by crater statistics a volcanic history for mars can be derived as follows early heavy bombardment of mars was accompanied and followed by small scale fluvial channeling extensive flood volcanism the plateau plains and ash shield volcanism in the cratered terrain shortly after this time less extensive flood volcanism continued to resurface the planet during formation of the northern southern hemisphere dichotomy central volcanism became more prominent with the development of the alba patera center as well as the older shields and domes of the northern hemisphere early tharsis and elysium regions the development of the tharsis and elysium uplifts may have triggered the release of large scale catastrophic floods producing large channels continued uplift and lithospheric thinning concentrated volcanic activity in the tharsis region producing large shield volcanoes and extensive lava plains both central vent and plains volcanism have been active throughout martian history but the volumes of extrusion have gradually decreased with time this is consistent with a moonlike thermal history involving a lithosphere of increasing thickness with time gradually turning off the volcanism although many questions remain regarding martian volcanism the viking data have provided a remarkable detailed overview of the probable nature of the volcanic history of mars

comparison of the mineral composition of the sediment found in two mars dunefields ogygis undae and gale crater three distinct endmembers identified abstract the composition of two dune fields ogygis undae and the ne sw trending dune field in gale crater the bagnold dune field and western dune field were analyzed using thermal emission spectra from the mars global surveyor mgs thermal emission spectrometer tes and the mars odyssey thermal emission imaging system themis the gale crater dune field was used as a baseline as other orbital compositional analyses have been conducted and in situ sampling results will soon be available results from unmixing thermal emission spectra showed a spatial variation between feldspar mineral abundances and pyroxene mineral abundances in ogygis undae other datasets including nighttime thermal inertia values also showed variation throughout the dune field one explanation proposed for this variation is a bimodal distribution of two sand populations this distribution is seen in some terrestrial dune fields the two dune fields varied in both mineral types present and in uniformity of composition these differences point to different source lithologies and different distances travelled from source material examining these differences further will allow for a greater understanding of aeolian processes on mars

morphology and composition of the surface of mars mars odyssey themis results the thermal emission imaging system themis on mars odyssey has produced infrared to visible wavelength images of the martian surface that show lithologically distinct layers with variable thickness implying temporal changes in the processes or environments during or after their formation kilometer scale exposures of bedrock are observed elsewhere airfall dust completely mantles the surface over thousands of square kilometers mars has compositional variations at 100 meter scales for example an exposure of olivine rich basalt in the walls of ganges chasma thermally distinct ejecta facies occur around some craters with variations associated with crater age polar observations have identified temporal patches of water frost in the north polar cap no thermal signatures associated with endogenic heat sources have been identified

determination of the drainage structure of a watershed using a digital elevation model and a digital river and lake network abstract distributed hydrological models require a detailed definition of a watershed s internal drainage structure the conventional approach to obtain this drainage structure is to use an eight flow direction matrix d8 which is derived from a raster digital elevation model dem however this approach leads to a rather coarse drainage structure when monitoring or gauging stations need to be accurately located within a watershed this is largely due to limitations of the d8 approach and the lack of information over flat areas and pits the d8 approach alone is also unable to differentiate lakes from plain areas to avoid these problems a new approach using a digital river and lake network drln as input in addition to the dem has been developed this new approach allows for an accurate fit between the drln and the modelled drainage structure which is represented by a flow direction matrix and a modelled watercourse network more importantly the identification of lakes within the modelled network is now possible the proposed approach which is largely rooted in the d8 approach uses the drln to correct modelled flow directions and network calculations for dem cells overlapped by the drln flow directions are determined using drln connections only the flow directions of the other dem cells are evaluated with the d8 approach which uses a dem that has been modified as a function of distance to the drln the proposed approach has been tested on the chaudiere river watershed in southern quebec canada the modelled watershed drainage structure showed a high level of coherence with the drln a comparison between the results obtained with the d8 approach and those obtained by the proposed approach clearly demonstrated an improvement over the conventionally modelled drainage structure the proposed approach will benefit hydrological models which require data such as a flow direction matrix a river and lake network and sub watersheds for drainage structure information

searching for the source regions of martian meteorites using mgs tes integrating martian meteorites into the global distribution of igneous materials on mars the objective of this study was to identify and map possible source regions for all 5 known martian meteorite lithologies basalt lherzolite clinopyroxenite orthopyroxenite and dunite using data from the mars global surveyor thermal emission spectrometer mgs tes we deconvolved the tes data set using laboratory spectra of 6 martian meteorites los angeles zagami alh a77005 nakhla alh 84001 and chassigny as end members along with atmospheric and surface spectra previously derived from tes data global maps 16 pixels degree of the distribution of each meteorite end member show that meteorite like compositions are not present at or above tes detectability limits over most of the planet s dust free regions however we have confidently identified local scale 100s1000s km2 concentrations of olivine and orthopyroxene bearing materials similar to alh a77005 chassigny and alh 84001 in nili fossae in and near ganges chasma in the argyre and hellas basin rims and in eos chasma nakhla like materials are identified near the detection limit throughout the eastern valles marineris region and portions of syrtis major basaltic shergottites were not detected in any spatially coherent areas at the scale of this study martian meteorite like lithologies represent only a minor portion of the dust free surface and thus are not representative of the bulk composition of the ancient crust meteorite like spectral signatures identified above tes detectability limits in more spatially restricted areas tens of km are targets of ongoing analysis

high resolution thermal inertia derived from the thermal emission imaging system themis thermal model and applications 1 thermal inertia values at 100 m per pixel are determined using nighttime temperature data from the thermal emission imaging system themis on the mars odyssey spacecraft producing the highest resolution thermal inertia data set to date themis thermal inertia values have an overall accuracy of 20 a precision of 10 15 and are consistent with both thermal emission spectrometer orbital and miniature thermal emission spectrometer surface thermal inertia values this data set enables the improved quantification of fine scale surface details observed in high resolution visible images in the tharsis region surface textures and crater rims observed in visible images have no corresponding variation in the themis thermal inertia images indicating that the dust mantle is pervasive at themis scales and is a minimum of a few centimeters and up to 1 2 m thick the thermal inertia of bed form material indicates particle diameters expected for aeolian sediments and these materials are likely currently saltating variations in the thermal inertia within interior layered deposits in hebes chasma can be distinguished and the thermal inertia is too low to be consistent with bedrock or a lava flow thus a secondary emplacement of volcanic material or a volcanic ash deposit is a more likely method of formation higher resolution themis thermal inertia enables the identification of exposed bedrock on the martian surface in nili patera and ares vallis bedrock material corresponds to distinct compositional and morphologic surfaces indicating that a specific unit is exposed and is likely currently being kept free of unconsolidated material by aeolian processes

the hydrology of lake bosumtwi a climate sensitive lake in ghana west africa abstract lake bosumtwi lying in a million year old meteor crater is hydrologically closed in spite of the wet humid climate in this part of ghana to understand this geographical enigma a water balance model that describes both the historical lake level record and the full range of lake levels observed in terrace deposits around the lake was developed the water balance model shows that the reception of rainfall by and evaporation from the lake surface are the dominant constituents of the water balance prior to 1969 the average rainfall of 1550 mm year 1 was generally equal to lake evaporation and the average annual rise of 30 cm year 1 was produced mostly by runoff from the small watershed around the lake since 1969 with a decreased rainfall of 1380 mm year 1 the combination of rainfall and runoff has nearly equaled lake evaporation resulting in a nearly steady lake level long term simulations show that stochastic climatic variations very similar to those observed in this century could produce the full range of lake levels observed in terrace deposits the low salinity of about 1 suggests that dissolved solutes were removed by lake overflow in the recent geological past

olivine and pyroxene diversity in the crust of mars datafromthe observatoire pour la mineralogie l9eau les glaces et l9activite omega on the mars express spacecraft identify the distinct mafic rock forming minerals olivine low calcium pyroxene lcp and high calcium pyroxene hcp on the surface of mars olivine and hcp rich regions are found in deposits that span the age range of geologic units however lcp rich regions are found only in the ancient noachian aged units which suggests that melts for these deposits were derived from a mantle depleted in aluminum and calcium extended dark regions in the northern plains exhibit no evidence of strong mafic absorptions or absorptions due to hydrated materials

grain size evolution and fractionation trends in an experimental regolith the comminution of blocky planetary surfaces into fine grained regoliths was simulated by impacting a fragmental gabbro target 200 times with stainless steel projectiles diameter 6 35 mm mass 1 2g vi 1 35 km s initially the target fragments were 2 32 mm in size with a mean diameter of 15 2 mm which was reduced to 0 4 mm after 200 shots for the first 60 shots comminution was linear with cumulative kinetic energy and thus essentially linear with time the comminution efficiency however decreased at later stages this could be due to a change in fracture mechanism from predominantly intergranular to predominantly intragranular and or due to a change in partitioning of the projectile s kinetic energy from collisional fragmentation or large fragments at early times to cratering in a progressively finer grained medium at later stages mineral specific preferential comminution is abundantly observed in the modal make up of various grain size fractions plagioclase comminutes more readily than pyroxenes plagioclase initially present at 54 vol comprises typically 65 70 of the 125 250 m fraction pyroxenes initially at 33 are depleted to 20 25 this fractionation occurs in the earliest samples analyzed and is not a time dependent phenomenon bulk chemical analyses reveal a corresponding increase in al2o3 cao and na2o and a decrease in feo and mgo the finest grain sizes are generally the most severely affected by differential comminution similar if not exactly identical trends are abundantly documented for lunar soil samples these experimental findings illustrate that differential comminution is capable of producing fractionation in the finest grain sizes they diminish the need for prominent lateral and vertical transport of components otherwise foreign to a lunar soil sampling site as postulated by some workers on the basis of multivariate chemical mixing models

thermal emission spectroscopy of the silica polymorphs and considerations for remote sensing of mars 1 the possible existence of silica rich rocks on mars requires consideration of all of the candidate forms of silica that might exist there we synthesized coesite and cristobalite and obtained natural samples of tridymite opal a and opal ct the thermal emission spectra of these silica phases were analyzed and related to their crystal structure and crystallinity structural differences between the polymorphs result in unique spectral character and the degree and type of crystal ordering in opal ct results in cristobalite or tridymite like spectral features these spectra will be useful for analysis of thermal emission spectrometer tes data from mars while silica polymorphs are not modeled in deconvolution of the two main tes surface type spectra this does not preclude the possible detection of local abundances of these minerals on mars spectral detection of silica phases on mars would have implications for the volcanic and alteration history of the planet

global mineral distributions on mars 1 determining the mineralogy of mars is an essential part of revealing the conditions of the surface and subsurface a deconvolution method was used to remove atmospheric components and determine surface mineralogy from thermal emission spectrometer data at 1 pixel per degree ppd minerals are grouped into categories on the basis of compositional and spectral similarity and global concentration maps are produced all binned pixels are fit well with rms errors of 0 005 in emissivity higher rms errors are attributed to short wavelength particle size effects on dust covered surfaces significant concentrations 0 10 of plagioclase high ca pyroxene sheet silicates high si glass and hematite are detected and display distributions consistent with previous studies elevated concentrations of plagioclase and high ca pyroxene are consistent with basaltic surfaces and are located in low albedo highlands regions north of 45 s significant concentrations of plagioclase and sheet silicates high si glass and low concentrations of high ca pyroxenes are consistent with andesitic surfaces and are concentrated in both southern and northern high latitude low albedo regions andesitic surfaces in the southern hemisphere have a lower spectral contrast than northern surfaces an isolated surface located in solis planum is spectrally distinct but compositionally similar to other surfaces interpreted to be andesitic in composition concentrations of olivine below the detection limit correctly identify its presence in two of three locations potassium feldspar low ca pyroxene basaltic glass olivine sulfate carbonate quartz and amphibole are not detected with confidence at 1 ppd the results presented here indicate a predominance of volcanic compositions within martian dust free surfaces

the huygens hellas giant dike system on mars implications for late noachian early hesperian volcanic resurfacing and climatic evolution two narrow broadly arcuate low ridges extend for 600 700 km in western terra tyrrhena mars crosscut ancient noachian terrain and are associated with early hesperian plains which cover 30 of mars geological relationships suggest that the ridges represent near surface erosional remnants of subsurface dikes solidified magma filled cracks that were responsible for the volcanic emplacement of the plains ridge width and geometry are consistent with very high effusion rate flood basalt eruptions emplacement events that would form smooth featureless plains and input significant volcanic gas into the atmosphere geological relationships suggest that the ridges were exposed by erosion fluvial sublimation eolian and partial removal of a regional volatile rich dust layer

geologic context of in situ rocky exposures in mare serpentis mars implications for crust and regolith evolution in the cratered highlands abstract global acquisition of infrared spectra and high resolution visible and infrared imagery has enabled the placement of compositional information within stratigraphic and geologic context mare serpentis a low albedo region located northwest of hellas basin is rich in spectral and thermophysical diversity and host to numerous isolated exposures of in situ rocky material most martian surfaces are dominated by fine grained particulate materials that bear an uncertain compositional and spatial relationship to their source thus location and characterization of in situ rock exposures is important for understanding the origin of highland materials and the processes which have modified those materials using spectral thermophysical and morphologic information we assess the local and regional stratigraphy of the mare serpentis surface in an effort to reconstruct the geologic history of the region the martian highlands in mare serpentis are dominated by two interspersed surface units which have distinct compositional and thermophysical properties 1 rock dominated surfaces relatively enriched in olivine and pyroxene and depleted in high silica phases and 2 sediment or indurated material depleted in olivine and pyroxene with relatively higher abundance of high silica phases this is a major previously unrecognized trend which appears to be pervasive in the mare serpentis region and possibly in other highland areas the detailed observations have led us to form two hypotheses for the relationship between these two units either 1 they are related through a widespread mechanical and or chemical alteration process where less mafic plains materials are derived from the mafic bedrock but have been compositionally altered in the process of regolith formation or 2 they are stratigraphically distinct units representing separate episodes of upper crust formation existing observations suggest that the second scenario is more likely in this scenario plains materials represent older degraded and possibly altered basement rock whereas the rocky exposures represent later additions to the crust and are probably volcanic in origin these hypotheses should be further testable with decimeter resolution imagery and meter resolution short wavelength infrared spectra

comparing trends in the southern annular mode and surface westerly jet abstractthis paper examines trends in the southern annular mode sam and the strength position and width of the southern hemisphere surface westerly wind jet in observations reanalyses and models from phase 5 of the coupled model intercomparison project cmip5 first the period over 1951 2011 is considered and it is shown that there are differences in the sam and jet trends between the cmip5 models the hadley centre gridded slp hadslp2r dataset and the twentieth century reanalysis the relationships between these trends demonstrate that the sam index cannot be used to directly infer changes in any one kinematic property of the jet the spatial structure of the observed trends in slp and zonal winds is shown to be largest but also most uncertain in the southeastern pacific to constrain this uncertainty six reanalyses are included and compared with station based observations of slp the cmip5 mean slp trends generally agree well with the direct observations despite some climatological biases

a sedimentary origin for intercrater plains north of the hellas basin implications for climate conditions and erosion rates on early mars understanding the origin volcanic or sedimentary and timing of intercrater plains is crucial for deciphering the geological evolution of mars we have produced a detailed geological map of the intercrater plains north of the hellas basin based on images from the mars express high resolution stereo camera the mars reconnaissance high resolution imaging science experiment and context erosional windows and fresh impact craters provide a way of studying the lithology of intercrater plain units they are composed predominantly of light toned sedimentary rocks with subhorizontal bedding over a broad extent greater than tens of kilometers showing cross bedding stratifications locally the broad extent geometry and flat topography of these sediments favor a formation by aqueous processes alluvial and lacustrine rather than airfall eolian and volcaniclastic the late noachian 3 7 ga sedimentary plains are locally covered by dark toned rough textured lava flows of late hesperian age 3 3 ga fe mg phyllosilicates were detected within sedimentary rocks whereas volcanic rocks contain pyroxene and lack signatures of alteration in agreement with interpretations made from texture and morphology in erosional windows the superimposition of sedimentary rocks by younger volcanic flows enables the estimation of an erosion rate of 1000 nm yr 1 during the hesperian period 3 3 3 7 ga thus our study shows that an intense sedimentary cycle occurred on the northern rim of the hellas basin before and during the late noachian leading to the formation of widespread sedimentary plains which were then eroded in agreement with a gradual change in the climatic conditions in this period and later covered by volcanic flows

improved global maps and 54 year history of wind work on ocean inertial motions 1 the global distribution and 54 year time dependence of the energy flux from the wind to near inertial motions is computed by driving a slab mixed layer model with ncep ncar reanalysis winds improving upon previous estimates alford 2001 watanabe and hibiya 2002 the slab model is solved spectrally with frequency dependent damping the resulting solutions are more physically sensible than the previous and more skillful at high latitudes where the inertial frequency approaches the 4 daily sampling of the reanalysis winds this enables alford s calculation whose domain was limited to 50 to be extended to the poles the high latitude reliability is demonstrated by direct comparison with a high resolution regional model remo in the ne atlantic the total power input 0 47 tw has increased by 25 since 1948 paralleling observed increases in extratropical cyclone frequency and intensity if believable the trend may have important consequences for modulation of the meridional overturning circulation

effect of precursor mineralogy on the thermal infrared emission spectra of hematite application to martian hematite mineralization 1 observations from the thermal emission spectrometer tes instrument aboard the mars global surveyor mgs spacecraft led to the discovery of two isolated deposits of gray crystalline hematite located in meridiani planum and aram chaos and several smaller deposits in valles marineris several pathways for formation of these hematite deposits have been proposed involving both aqueous and nonaqueous processes this work uses the precise shape and position of spectral features in the martian hematite thermal emission spectrum to constrain hematite formation pathways thermal infrared emission spectra x ray powder diffraction patterns mossbauer spectra and transmission electron microscope tem photomicrographs were obtained for synthetic and natural hematite samples derived by 1 dehydroxylation of fine grained goethite and 2 oxidation of magnetite collectively the instrumental analyses show that the mineralogical composition and crystal morphology of precursor samples and the time and temperature conditions under which decomposition to hematite occur determine the crystallinity and crystal morphology of the hematite product comparison of laboratory and mgs tes spectra shows that the martian hematite spectra correspond closely with a synthetic hematite sample derived by pseudomorphic and topotactic dehydroxylation of goethite at 300 c spectra of goethite precursor samples dehydroxylated at higher temperatures provide increasingly poor fits spectra of hematite samples derived by high temperature thermal oxidation of magnetite are also poorer fits to the martian hematite spectrum thermal emission spectra of goethites heated at lower temperatures are characterized by the spectral signatures of both hematite and goethite and are not consistent with the martian spectra the characteristic that distinguishes the synthetic hematite sample with the mars like spectral signature from the other synthetic hematite samples is the high proportion of crystal surfaces that are crystallographic 001 faces c faces for the former but not the latter the high proportion of 001 face area results because the largest surface of the lath shaped hematite particles is the 001 face as determined by tem thus a possible formation pathway for hematite in meridiani planum aram chaos and valles marineris is precipitation of goethite from aqueous solutions as lath shaped crystals possibly as a stain cement and or massive deposit followed by pseudomorphic and topotactic dehydroxylation to hematite at temperatures below 300 c

visible and near infrared multispectral analysis of rocks at meridiani planum mars by the mars exploration rover opportunity multispectral measurements in the visible and near infrared of rocks at meridiani planum by the mars exploration rover opportunity s pancam are described the pancam multispectral data show that the outcrops of the burns formation consist of two main spectral units which in stretched 673 535 432 nm color composites appear buff and purple colored these units are referred to as the hfs and lfs spectral units based on higher and lower values of 482 to 535 nm slope spectral characteristics are consistent with the lfs outcrop consisting of less oxidized and the hfs outcrop consisting of more oxidized iron bearing minerals the lfs surfaces are not as common and appear primarily at the distal ends of outcrop layers and on steep more massive surfaces locations that are subject to greater eolian erosion consequently the hfs surfaces are interpreted as a weathering rind further inherent spectral differences between layers and between different outcrop map units both untouched and patches abraded by the rover s rock abrasion tool are also described comparisons of the spectral parameters of the meridiani outcrop with a set of laboratory reflectance measurements of fe 3 bearing minerals show that the field of outcrop measurements plots near the fields of hematite ferrihydrite poorly crystalline goethite and schwertmannite rind and fracture fill materials observed intermittently at outcrop exposures are intermediate in their spectral character between both the hfs and lfs spectral classes and other less oxidized surface materials basaltic sands spherules and cobbles

a new method for the semiquantitative determination of major rock forming minerals with thermal infrared multispectral data application to themis infrared data 1 we have developed a new method least residual iterative spectral mixture analysis lrisma to semiquantitatively determine major rock forming minerals feldspar pyroxene olivine high silica phases and quartz with multispectral thermal infrared data sublibraries of minerals are generated from a master library of minerals based on prior knowledge to produce a suite of realistic mineral end member combinations to fit the target spectra mineral abundances that correspond to the least root mean square errors best fit generally agree best with previous petrographic studies of laboratory measured rock samples and thermal infrared hyperspectral analysis of materials on the surface of mars given the greatly reduced spectral range and resolution of thermal emission imaging system themis spectra the accuracy and reproducibility of lrisma is 4 16 and 5 20 respectively while the accuracy of petrographic and previous hyperspectral studies is 5 15 lrisma can be applied to semiquantitatively refine the bulk surface mineralogy of small scale 1 km2 geologic features with high quality themis spectral data high surface temperature 260 k low atmospheric opacity total ice 0 04 and total dust 0 15 with the ultimate goal of better understanding regional geologic processes

a distributed surface flow model for watersheds with large water bodies and channel loops summary large water bodies 25 and 172 km 2 and channel loops exist in the study watershed the tone river basin japan in order to overcome the difficulties in routing the two dimensional surface flows in the water bodies and channel loops the large scale unified and optimization model has been developed in the model the ordering scheme based on the freely seriate tree structure is adopted to order the stream network with channel loops the diffusive wave approximation of the two dimensional free surface flow equations are employed as the governing equations for the surface flows including both overland and channel flows both overland and channel flows are placed in the same physical domain in which a channel grid cell exchanges mass and momentum with the eight adjacent grid cells of overland channels and water bodies and consequently it is simple and easy to incorporate water bodies and channel loops into the model the finite difference method based on the staggered grid scheme is utilized to discretize the governing equations and the optimization numerical scheme simple is employed to solve the finite difference equations using a tri diagonal matrix this paper focuses primarily on the formulation of the model limited model calibration and validation using point streamflow data in the tone river basin are presented and more complete evaluation of the distributed outputs is left for future work

acid sulfate weathering of synthetic martian basalt the acid fog model revisited the acid fog model has received considerable attention as a model of soil formation on mars previous evaluations of this model have focused on experimental weathering of terrestrial basalt samples however these samples differ significantly from what now is thought to be typical of martian basalt the acid fog model is tested here using synthetic basaltic analogs derived from mars pathfinder soil and rock compositions reaction of synthetic basalt with various acidic solutions and subsequent evaporation has led to the formation of several putative secondary mineral phases many of these phases were not produced in prior experimental studies aimed at aqueous interactions on mars of these alteration phases mg fe ca and al sulfates were identified in addition secondary ferric oxide phases formed via rapid fe oxidation under relatively high ph levels buffered by basalt dissolution amorphous silica is a ubiquitous product in these experiments and has formed by precipitation from solution and by the dissolution of minerals and glasses leaving behind leached surface layers composed of residual silica the secondary products formed in these experiments demonstrate the importance of primary mineralogy when testing models of aqueous interactions on mars new constraints are placed on both the reactivity of primary basalt and the secondary mineralogy present at the martian surface copyright 2004 by the american geophysical union

olivine dissolution by acidic fluids in argyre planitia mars evidence for a widespread process compositional and morphological analyses of basin rim units in argyre planitia are con sistent with local olivine rich materials that become relatively olivine poor in the process of being transformed from rocky materials to fi particulate regolith where high thermal inertia rocky surfaces are observed the composition is more mafi c than the surrounding fi nes this relationship between rocks and soils appears to be common on mars as a similar pattern is observed in other locations such as gusev crater isidis planitia and nili fossae despite the lack of local detectable alteration products these trends may be an indication that most martian dark regions are not similar in composition to the primary igneous composition from which they are derived the martian crust may be signifi cantly more mafi c and alteration of these surfaces may be more pervasive than has been inferred from the bulk surface mineral ogy derived from orbital observations

stratified ekman layers under fair weather conditions the time averaged wind driven current forms a spiral in which the current vector decays and turns clockwise with increasing depth these spirals resemble classical ekman spirals they differ in that their rotation depth scale exceeds the e folding depth of the speed by a factor of 2 to 4 and they are compressed in the downwind direction a related property is that the time averaged stress is evidently not parallel to the time averaged vertical shear we develop the hypothesis that the flat spiral structure may be a consequence of the temporal variability of stratification within the upper 10 20 m of the water column this variability is associated primarily with the diurnal cycle and can be treated by a time dependent diffusion model or a mixed layer model the latter can be simplified to yield a closed solution that gives an explicit account of stratified spirals and reasonable hindcasts of midlatitude cases at middle and higher latitudes the wind driven transport is found to be trapped mainly within the upper part of the ekman layer the diurnal warm layer at tropical latitudes the effects of diurnal cycling are in some ways less important and ekman layer currents are likely to be significant to much greater depths in that event the lower part of the ekman layer is likely to be affected by stratification variability that may be nonlocal

mars surface diversity as revealed by the omega mars express observations the observatoire pour la mineralogie l eau les glaces et l activite omega investigation on board the european space agency mars express mission is mapping the surface composition of mars at a 0 3 to 5 kilometer resolution by means of visible near infrared hyperspectral reflectance imagery the data acquired during the first 9 months of the mission already reveal a diverse and complex surface mineralogy offering key insights into the evolution of mars omega has identified and mapped mafic iron bearing silicates of both the northern and southern crust localized concentrations of hydrated phyllosilicates and sulfates but no carbonates and ices and frosts with a water ice composition of the north polar perennial cap as for the south cap covered by a thin carbon dioxide ice veneer

the rocks of gusev crater as viewed by the mini tes instrument 1 the miniature thermal emission spectrometer mini tes on board the mars exploration rover spirit is part of a payload designed to investigate whether a lake once existed in gusev crater mini tes has observed hundreds of rocks along the rover s traverse into the columbia hills yielding information on their distribution bulk mineralogy and the potential role of water at the site although dust in various forms produces contributions to the spectra we have established techniques for dealing with it all of the rocks encountered on the plains traverse from the lander to the base of the columbia hills share common spectral features consistent with an olivine rich basaltic rock known as adirondack class beginning at the base of the west spur of the columbia hills and across its length the rocks are spectrally distinct from the plains but can be grouped into a common type called clovis class these rocks some of which appear as in place outcrop are dominated by a component whose spectral character is consistent with unaltered basaltic glass despite evidence from other rover instruments for significant alteration the northwest flank of husband hill is covered in float rocks known as wishstone class with spectral features that can be attributed uniquely to plagioclase feldspar a phase that represents more than half of the bulk mineralogy rare exceptions are three classes of basaltic exotics found scattered across husband hill that may represent impact ejecta and or float derived from local intrusions within the hills the rare outcrops observed on husband hill display distinctive spectral characteristics the outcrop called peace shows a feature attributable to molecular bound water and the outcrop that hosts the rock called watchtower displays a dominant basaltic glass component despite evidence from the rover s payload for significant alteration of some of the rocks no unambiguous detection of crystalline phyllosilicates or other secondary silicates has been observed by mini tes the mineralogical results supplied by mini tes provide no clear evidence that a lake once existed in gusev crater

areally extensive surface bedrock exposures on mars many are clastic rocks not lavas areally extensive exposures of intact olivine pyroxene enriched rock as well as feldspar enriched rock are found in isolated locations throughout the martian highlands the petrogenetic origin s of these rock units are not well understood but some previous studies favored an effusive volcanic origin partly on the basis of distinctive composition and relatively high thermal inertia here we show that the regolith development crater retention and morphological characteristics for many of these bedrock plains are not consistent with competent lavas and reinterpret the high thermal inertia orbital signatures to represent friable materials that are more easily kept free of comminution products through eolian activity candidate origins include pyroclastic rocks impact generated materials or detrital sedimentary rocks olivine pyroxene enrichments in bedrock plains relative to surrounding materials could have potentially formed through deflation and preferential removal of plagioclase

a preliminary estimate of the stokes dissipation of wave energy in the global ocean 1 the turbulent reynolds stresses in the upper layers of the ocean interact with the vertical shear of the stokes drift velocity of the wave field to extract energy from the surface waves the resulting rate of dissipation of wind waves in the global ocean is about 2 5 tw on the average but can reach values as high as 3 7 tw making it as important as the dissipation of wave energy in the surf zones around the ocean margins more importantly the effect of stokes dissipation is felt throughout the mixed layer it also contributes to langmuir circulations unfortunately this wave dissipation mechanism has hitherto been largely ignored in this note we present a preliminary estimate of the stokes dissipation rate in the global oceans based on the results of the wavewatch iii model for the year 2007 to point out its potential importance seasonal and regional variations are also described

the formation of infilled craters on mars evidence for widespread impact induced decompression of the early martian mantle flat floored craters have long been recognized on mars with early work hypothesizing a sedimentary origin more recently high resolution thermal inertia measurements show that these craters contain some of the rockiest materials on the planet inconsistent with poorly consolidated sedimentary materials in this study the distribution physical properties morphology and thermal inertia and composition of these craters are thoroughly investigated over the entire planet the majority of the 2800 rocky crater floors identified are concentrated in the low albedo 0 1 0 17 cratered southern highlands these craters were infilled at 3 5 ga and are associated with the highest thermal inertia values and some of the most mafic materials identified on the planet although several processes may have led to the formation of the crater floors the most likely scenario is volcanic infilling through fractures created by the impact event the primitive magma source directly results from decompression melting of the martian mantle by the removal of the crustal material excavated by the impactor volcanic infilling of craters by decompression melting appears to only have occurred in early martian history when the lithosphere was still relatively thin and the thermal gradient was high this process was widespread and responsible for the eruption of significant volumes of primitive material inside and likely outside of craters impact induced decompression melting of the martian mantle accounts for the unusual infilling of martian craters and is a widespread planetary process that has gone previously undocumented

global distribution of bedrock exposures on mars using themis high resolution thermal inertia 1 we investigate high thermal inertia surfaces using the mars odyssey thermal emission imaging system themis nighttime temperature images 100 m pixel spatial sampling for this study we interpret any pixel in a themis image with a thermal inertia over 1200 j m 2 k 1 s 1 2 as bedrock which represents either in situ rock exposures or rock dominated surfaces three distinct morphologies ranked from most to least common are associated with these high thermal inertia surfaces 1 valley and crater walls associated with mass wasting and high surface slope angles 2 floors of craters with diameters 25 km and containing melt or volcanics associated with larger high energy impacts and 3 intercrater surfaces with compositions significantly more mafic than the surrounding regolith in general bedrock instances on mars occur as small exposures less than several square kilometers situated in lower albedo 350 j m 2 k 1 s 1 2 and relatively dust free dust cover index 0 95 regions however there are instances that do not follow these generalizations most instances are concentrated in the southern highlands with very few located at high latitudes poleward of 45 n and 58 s suggesting enhanced mechanical breakdown probably associated with permafrost overall mars has very little exposed bedrock with only 960 instances identified from 75 s to 75 n with likely 3500 km 2 exposed representing 1 ofthe total surface area these data indicate that mars has likely undergone large scale surface processing and reworking both chemically and mechanically either destroying or masking a majority of the bedrock exposures on the planet

experimental epithermal alteration of synthetic los angeles meteorite implications for the origin of martian soils and identification of hydrothermal sites on mars 1 the dissolution behavior and secondary minerals generated by experimental alteration of a synthetic los angeles basaltic shergottite la were evaluated at epithermal 75 c conditions starting ph values of 1 1 and 3 6 and water rock ratios ranging from 100 to 2000 were studied using flow through and batch reactor experimental apparatus dissolution of plagioclase dominates effluent solution chemistry under all experimental conditions little mg is released to solution because nearly 100 of the mg in unaltered la is contained in pyroxene m1 sites which are relatively resistant to dissolution secondary minerals generated include siliceous residue amorphous sio2 lepidocrocite and ferrihydrite anhydrite alunogen rhomboclase ferrinatrite halite and unidentified ca and na sulfates the dominance of alteration products of plagioclase suggests that la type basalts have not contributed significantly to the martian soils the search for hydrothermal sites by remote sensing may be hampered by the general similarity of the alteration products found in the near surface epithermal environment to those thought to exist in martian soils sulfates iron oxyhydroxides amorphous silica however the unique chemical composition of secondary products formed by la alteration may make detection of recent hydrothermal alteration of evolved basaltic rocks more straightforward in addition alteration in terrestrial epithermal environments associated with mafic to intermediate volcanic rocks generally produces abundant sulfides and kaolinite two potentially unique mineral phases which might also indicate the presence of active or extinct hydrothermal systems

emission spectroscopy of clay minerals and evidence for poorly crystalline aluminosilicates on mars from thermal emission spectrometer data 1 to understand the aqueous history of mars it is critical to constrain the alteration mineralogy of the martian surface previously published analyses of thermal infrared 6 25 m remote sensing data of mars suggest that dark regions have 15 20 clay minerals however near infrared 1 3 m spectral results generally do not identify widespread clay minerals thermal infrared detections of clays on mars are difficult to interpret owing in part to the relative paucity of published spectral analyses of clay minerals and clay bearing materials using similar spectra thermal infrared emission spectra in this study we present an analysis of the thermal emission spectral features 6 25 m or 400 1650 cm 1 of a suite of clay mineral reference materials and clay bearing rocks linking their spectral features to the crystal chemical properties of the clays on the basis of this context provided by the emission spectral analysis of clay minerals and clay bearing rocks we reconsider the evidence for clay minerals on mars from thermal emission spectrometer tes results we propose that global scale clay abundances determined from tes probably represent a geologically significant surface component though they may actually correspond to poorly crystalline aluminosilicates with similar si o ratios to clay minerals 0 3 0 4 rather than well crystalline clays if clay minerals or clay like materials on mars are poorly crystalline and or dessicated they may be detectable in the thermal infrared but not easily detected with near infrared data sets

evidence for extensive olivine rich bedrock on mars color infrared observations of an area around the nili fossae acquired by the mars odyssey thermal emission imaging system have been used to map the regional distribution and geologic context of olivine rich materials that first were identified from mars global surveyor thermal emission spectrometer data spectral thermal geomorphic and topographic data demonstrate that the majority of olivine rich material is in the form of inplace layered rock covering an area roughly four times larger than previously recognized some high olivine concentrations are associated with spatially small areas dominated by sediments we favor olivine rich basalts as the origin of the observed olivine enrichment although several hypotheses are viable

global investigation of olivine on mars insights into crust and mantle compositions 1 we present the distribution of olivine on mars derived from spectral parameters based on the 1 m olivine absorption band the olivine can be defined with respect to two spectral end members type 1 corresponds to olivine with low iron content and or small grain size and or small abundance and type 2 which corresponds to olivine with higher iron content and or larger grain size and or larger abundance the spatial and statistical analysis of the global olivine distribution points out five major geological settings where olivine is detected 1 early hesperian olivine bearing smooth crater floors and flat intercrater plains throughout the southern highlands 2 olivine deposits around the three main basins argyre hellas and isidis 3 olivine in intercrater dunes crater ejecta or extended deposits in the northern plains 4 olivine associated with outcrops and sand in the floor of valles marineris and 5 olivine bearing butte outcrops in the vicinity of hellas the geological context the age and the composition of the olivine detections associated with these five major geological settings are detailed their origin and the implication of their occurrence on the composition of the martian mantle and crust as well as on the evolution of mars volcanism are discussed

in situ and experimental evidence for acidic weathering of rocks and soils on mars experimental data for alteration of synthetic martian basalts at ph 0 1 indicate that chemical fractionations at low ph are vastly different from those observed during terrestrial weathering rock surface analyses from gusev crater are well described by the relationships apparent from low ph experimental alteration data a model for rock surface alteration is developed which indicates that a leached alteration zone is present on rock surfaces at gusev this zone is not chemically fractionated to a large degree from the underlying rock interior indicating that the rock surface alteration process has occurred at low water to rock ratio the geochemistry of natural rock surfaces analyzed by apxs is consistent with a mixture between adhering soil dust and the leached alteration zone the chemistry of rock surfaces analyzed after brushing with the rat is largely representative of the leached alteration zone the chemistry of rock surfaces analyzed after grinding with the rat is largely representative of the interior of the rock relatively unaffected by the alteration process occurring at the rock surface elemental measurements from the spirit opportunity pathfinder and viking 1 landing sites indicate that soil chemistry from widely separated locations is consistent with the low ph low water to rock ratio alteration relationships developed for gusev rocks soils are affected principally by mobility of fe and mg consistent with alteration of olivine bearing basalt and subsequent precipitation of fe and mg bearing secondary minerals as the primary control on soil geochemistry copyright 2006 by the american geophysical union

mosaicking of global planetary image datasets 1 techniques and data processing for thermal emission imaging system themis multi spectral data 1 the mosaicking of global planetary data sets allows for the examination of local regional and global scale processes on all planetary bodies processing techniques that allow us and other users to crate mosaics of tens of thousands of images are documented along with the associated errors introduced by each image processing algorithm these techniques e g non uniformity correction running contrast stretches line and row correlated noise removal and random noise removal were originally developed for the 2001 mars odyssey thermal emission imaging system themis infrared multispectral imager data but can be adapted and applied to other data sets by the alteration of input parameters the techniques for mosaicking planetary image data sets e g image registration blending and normalization are also presented along with the generation of qualitative and quantitative products these techniques are then applied to generate themis daytime and nighttime infrared viking context imager ctx and mars orbiter camera moc visible mosaics using a variety of input and output types at a variety of scales by creating mosaics of the same area using different data sets such as those that illustrate compositional diversity thermophysical properties or small scale morphology it is possible to view the surface of the planet and geologic problems through many different perspectives in addition to the techniques used to create large scale seamless mosaics we also present the themis daytime and nighttime relative temperature global mosaics which are the highest resolution 100m pixel global scale data sets available for mars to date

feldspathic rocks on mars compositional constraints from infrared spectroscopy and possible formation mechanisms rare feldspar dominated surfaces on mars were previously reported based on near infrared nir spectral data and were interpreted to consist of anorthosite or felsic rocks using thermal infrared tir data over the feldspar detections with the largest areal extent in nili patera and noachis terra we rule out felsic interpretations basaltic or anorthositic compositions are consistent with tir measurements but the geologic contexts for these regions do not support a plutonic origin laboratory nir spectral measurements demonstrate that large plagioclase crystals 840 m can be detected in mixtures with as much as 50 vol mafics which is higher than the previously stated requirement of no more than 15 mafics thus anorthositic or felsic interpretations need not be invoked for all nir based feldspar detections plagioclase enriched basaltic eruptive products can be formed from martian basalts through partial crystallization at the base of a thick crust followed by low pressure crystallization of the residual liquids

a 3 5 ga record of water limited acidic weathering conditions on mars abstract the secondary mineral budget on earth is dominated by clay minerals al hydroxides and fe oxides which are formed under the moderate ph high water to rock ratio conditions typical of earth s near surface environment in contrast geochemical analyses of rocks and soils from landed missions to mars indicate that secondary mineralogy is dominated by mg fe ca sulfates and fe oxides this discrepancy can be explained as resulting from differences in the chemical weathering environment of earth and mars we suggest that chemical weathering processes on mars are dominated by 1 a low ph sulfuric acid rich environment in which the stoichiometric dissolution of labile mineral phases such as olivine and apatite fe ti oxides is promoted and 2 relatively low water to rock ratio such that other silicate phases with slower dissolution rates e g plagioclase pyroxene do not contribute substantially to the secondary mineral budget at the martian surface under these conditions al mobilization is limited and the formation of significant al bearing secondary phases e g clays al hydroxides al sulfates is inhibited the antiquity of rock samples analyzed in situ on mars suggest that water limited acidic weathering conditions have more than likely been the defining characteristic of the martian aqueous environment for billions of years

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

extended surface exposures of granitoid compositions in syrtis major mars 1 the number of quartz and feldspar rich surfaces identified in northwestern syrtis major has been extended beyond previously reported results to a region of about 230 by 125 km thermal emission imaging system infrared data were used to locate surfaces spectrally identical to previously reported central peak units in syrtis major these surfaces are indicative of the production of highly differentiated magmas though it is possible that the granitoid exposures add to the variety of igneous compositions associated with the syrtis major volcanic construct the geologic context of these exposures suggests a formation that predates syrtis major

discovery of olivine in the nili fossae region of mars we have detected a 30 000 square kilometer area rich in olivine in the nili fossae region of mars nili fossae has been interpreted as a complex of grabens and fractures related to the formation of the isidis impact basin we propose that post impact faulting of this area has exposed subsurface layers rich in olivine linear mixture analysis of thermal emission spectrometer spectra shows surface exposures of 30 olivine where the composition of the olivine ranges from fo30 to fo70

martian dunite nwa 2737 integrated spectroscopic analyses of brown olivine received 5 october 2007 revised 13 december 2007 accepted 6 march 2008 published 18 june 2008 1 a second martian meteorite has been identified that is composed primarily of heavily shocked dunite northwest africa nwa 2737 this meteorite has several similarities to the chassigny dunite cumulate but the olivine is more mg rich and most notably is very dark and visually brown carefully coordinated analyses of nwa 2737 whole rock and olivine separates were undertaken using visible and near infrared reflectance

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

the role of aqueous alteration in the formation of martian soils abstract martian equatorial dark regions are dominated by unweathered materials and it has often been assumed that they have not been significantly altered from their source lithology the suite of minerals present is consistent with a basaltic composition and there has been no need to invoke additional processes to explain the origin of these compositions we have begun to question this result based on detailed observations using a variety of datasets locally derived dark soils have a mineralogy distinct from that of adjacent rocky surfaces most notably a lower olivine content this pattern is common for many surfaces across the planet previous work using detailed measurements acquired within the gusev plains has shown that olivine dissolution via acidic weathering may explain chemical trends observed between rock rinds and interiors mineralogical trends obtained from rocks and soils within the gusev plains are more prominent than the elemental trends and support previous results that indicate that dissolution of olivine has occurred however clear differences are also present in elemental abundances that indicate a variety of inputs and processes are likely responsible for the formation of martian dark soils despite the potential complexity of source materials and processes it appears that most martian dark regions have likely experienced aqueous alteration and chemical weathering appears to be closely linked to the mechanical breakdown of materials regardless of the responsible mechanism there appears to be a general though not perfect correlation between elevated olivine abundance and high thermal inertia surfaces on mars

analysis of terrestrial and martian volcanic compositions using thermal emission spectroscopy 1 determination of mineralogy chemistry and classification strategies we have examined and applied existing classification schemes for volcanic rocks and developed new schemes using thermal emission spectra of terrestrial volcanic rocks laboratory thermal infrared spectra 5 25 m at 2 cm 1 spectral sampling deconvolved modal mineralogies and derived mineral and bulk rock chemistries were used to distinguish basalt basaltic andesite andesite and dacite modal mineralogies derived from linear deconvolution of terrestrial volcanic rocks were compared to modes measured by an electron microprobe phase mapping technique to determine the accuracy of linear deconvolution in modeling specific mineral abundances one standard deviations of the absolute differences between modeled and measured mineral abundances range from 2 4 to 12 2 vol with an average standard deviation of 4 8 vol being in agreement with average uncertainties calculated in previous studies weighted average compositions of feldspars in the deconvolution generally overlap the measured ranges of plagioclase compositions and the presence of low calcium and high calcium pyroxenes was correctly identified bulk chemistries of volcanic rocks were derived with a relatively high degree of accuracy 1 standard deviations ranging from 0 4 to 2 6 vol by combining the compositions of spectrally modeled phases in proportion to their relative abundances in a particular sample these data were collectively used to examine existing and develop new volcanic rock classification schemes however no single classification scheme was effective in accurately classifying all samples multiple steps of classification were required to distinguish volcanic rocks reflecting the mineralogic diversity and continuum of compositions that exists in volcanic rock types in a companion paper hamilton et al this issue these schemes are applied to the classification of martian surface compositions

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

mineralogy of volcanic rocks in gusev crater mars reconciling mossbauer alpha particle x ray spectrometer and miniature thermal emission spectrometer spectra 1 complete sets of mineral abundances for relatively unaltered volcanic or volcaniclastic rocks in gusev crater have been determined by modeling mossbauer subspectral areas as mineral weight percentages and combining those percentages with the proportions of iron free minerals not detected by mossbauer normative plagioclase apatite and chromite as calculated from alpha particle x ray spectrometer apxs chemical analyses comparisons of synthetic thermal emission spectra calculated for these mineral modes with measured miniature thermal emission spectrometer mini tes spectra for the same rock classes show either good agreements or discrepancies that we attribute to sodic plagioclase compositions or unmodeled sulfate glass or pigeonite the normative compositions of olivine pyroxene and feldspar calculated from apxs data are consistent with spectroscopic constraints on mineral compositions systematic variations between olivine abundances in apxs norms which sample tens of micrometers depth and olivine proportions measured by mossbauer which sample hundreds of micrometers depth support the hypothesis that dissolution of olivine by acidic fluids has occurred on weathered rock surfaces

a study of low albedo deposits within amazonis planitia craters evidence for locally derived ultramafic to mafic materials 1 we studied low albedo deposits in the floors of craters within the amazonis planitia region using infrared data from mars global surveyor thermal emission spectrometer tes and mars odyssey thermal emission imaging system themis high resolution visible images from the mars orbiter camera and themis and topographic data from the mars orbiter laser altimeter these deposits are found within subdued to sharp rimmed craters that impacted into thick basaltic lava flows from olympus mons these lava flows flooded the region and were subsequently eroded by aeolian processes tes spectral modeling of the low albedo deposits reveals a mineralogy that is dominated by mafic minerals olivine pyroxene with a derived bulk chemistry that ranges from ultramafic to mafic 40 52 wt sio2 in composition these bulk compositions are comparable to some martian lithologies but represent some of the lowest silica contents identified on mars the compositional range could be produced by either primary igneous processes or subsequent alteration by aeolian processes the spatial distribution of the compositions reveals weak to absent groupings and does not distinguish between the igneous or aeolian scenarios in some craters possible local sources have been identified within the crater walls floors and interiors local sources may be present in additional craters but obscured by dust no regional sources were identified within a reasonable distance in terms of sand transport but may also be obscured by dust therefore the low albedo deposits probably resulted from aeolian erosion of local intracrater basaltic materials that were subsequently redistributed within the floors of these craters