extreme detached dust layers near martian volcanoes evidence for dust transport by mesoscale circulations forced by high topography modeling suggests that thermal circulations over mars s highest volcanoes transport water vapor and dust from the surface into the middle atmosphere forming detached layers in these constituents intense vertical mixing also takes place in regional and global dust storms which can generate detached layers that are extreme in both altitude and magnitude here we employ observations by the mars climate sounder mcs on board mars reconnaissance orbiter taking advantage of improved vertical coverage in mcs s aerosol retrievals to discover a new class of extreme detached dust layers eddls observed during minimal dust storm activity and furthermore distinguished by their potentially large and measurable horizontal extent 1000 km these eddls cluster near olympus mons and the tharsis montes from which they likely originate the existence of these eddls suggests that vertical mixing by topographic circulations can be much stronger than previously modeled and more frequent than previously observed

an aerodynamic roughness length map derived from extended martian rock abundance data many boundary layer processes simulated within a mars general circulation model mgcm including the description of the processes controlling dust rising from the martian surface are highly sensitive to the aerodynamic roughness length z0 on the basis of rock size frequency distributions inferred from different martian landing sites and earth analog sites we have first established that lognormal modeled rock size frequency distributions are able to reproduce correctly the observed martian rock populations we have validated the hypothesis that the rock abundance of a given area could be estimated at a first order from its thermophysical properties namely its thermal inertia i and its albedo we have demonstrated the possibility of using rock abundance to estimate the roughness density on mars and to retrieve subsequently the aerodynamic roughness length by using semi empirical relationships based on terrestrial wind tunnel and field measurements by combining our methodology with remote sensing measurements of the thermal emission spectrometer aboard mars global surveyor we have derived a global map of the aeolian aerodynamic roughness length with a 1 8 1 8 resolution over the entire martian surface contrary to what is often assumed the martian aeolian aerodynamic roughness length is spatially highly heterogeneous at the fullest resolution the martian aerodynamic roughness length varies from 10 3 cm to 2 33 cm about 84 of the martian surface seems to be characterized by an aeolian aerodynamic roughness length value lower than 1 cm the spatially uniform value that most of the mgcms simulations have assumed recently since the aerodynamic roughness length z0 is a key parameter in deriving the erosion threshold wind velocities we anticipate a significant impact of our findings on the efficiencies for lifting dust in future mgcms

possible dust devils vortices on mars this paper presents the results of a study of local vortices and dust devils on mars as observed by viking landers 1 and 2 it is found that these vortices are most common during martian spring and summer as occurs on earth seven of the vortices involve wind speeds that may raise dust from the martian surface there is no indication that these possible dust devils contribute to the planet wide spread of major dust storms however it appears that they may help in maintaining the atmospheric dust content the data indicate that there is no preference in rotation direction at least to core diameters of 300 m corresponding to a region of influence of about 3 km diameter

monitoring mars with the hubble space telescope 1990 1991 observations images of mars obtained using the planetary camera on the hubble space telescope during 1990 and 1991 are described and analyzed multispectral images of mars record the martian season between ls 348 and 60 corresponding to late winter and spring in the northern hemisphere the wavelengths of these observations varied between 230 nm in the ultraviolet and 890 nm in the near infrared we use these images to discuss atmospheric and polar phenomena to constrain the aerosols and ozone in the martian atmosphere and to compare surface albedo features within this data set as well as with previous observations two methods are used to constrain the opacity of the martian atmosphere comparisons of ultraviolet images with atmospheric scattering models and examination of contrast changes of surface features observed at visible wavelengths our observations are consistent with a mars which was quite different from the planet when it was viewed by viking we estimate an upper limit of 0 1 for equatorial dust opacity near vernal equinox compared to values of 0 4 to 0 5 measured in chryse by viking lander 1 later at ls 60 an upper limit of 0 2 was found for dust in the southern hemisphere except for suggestions of local dust activity near the north polar cap in late spring there was no visual evidence of dust storms on the planet the hartley band of ozone is within the f230w filter bandpass and the 230w 336w ratio is therefore sensitive to ozone high latitude ozone is observed at a concentration similar to that observed by mariner 9 a seasonal dependence in ozone concentration was observed with concentration decreasing at northern arctic latitudes and increasing at southern midlatitudes as ls increases from 350 to 60 despite the difference in dust loading the behavior of condensate clouds and the recession of the north polar cap are consistent with those observed during viking years late winter images of the north polar region reveal an active north polar hood with a maximum uv opacity of about 0 25 near 50 latitude the hood seems to have an annular form with the central polar regions having smaller opacity clouds observed in the northern hemisphere to the south of the hood boundary are suggestive of fronts similar to those observed during the mariner 9 mission a diurnal variation in the hood clouds which is anti correlated with the amount of water vapor in the atmosphere is noted spring images show significant clouds in the tharsis elysium and arabia regions the most optically thick components of these clouds are those near elysium alba patera and tithonius in the afternoon although these regions also are bright on the morning limb the cloud associated with elysium had the largest optical depth for a cloud in the uv 0 4 most of the hst monitoring sequences were targeted on the syrtis major region an area which was intensively studied during the viking mission during viking there were major changes in the region which were attributed to the two major 1977 global dust storms on mars our series of images was projected onto map grids and photometrically corrected in order to study changes in the syrtis albedo features to first order syrtis does not change over the time period of these observations as would have been expected if they followed major global dust storms during the preceding season images were deconvolved using the richardson lucy iterative algorithm to remove the defocussing effects of the spherical aberration of the hst primary even when mars subtended less than 5 arcsec in may 1991 the images were scientifically useful and comparable to photographic images obtained at opposition although the data are subject to the solar pointing constraint for hst the relatively slow movement of the allowed observation window which is more than one half martian year with respect to the martian seasons will permit us to address the question of major variations in the martian atmosphere

a survey of martian dust devil activity using mars global surveyor mars orbiter camera images 1 a survey of dust devils using the mars global surveyor mgs mars orbiter camera moc wide and narrow angle wa and na images has been undertaken the survey comprises two parts 1 sampling of nine broad regions from september 1997 to july 2001 and 2 a focused seasonal monitoring of variability in the amazonis region an active dust devil site from march 2001 to april 2004 for part 1 dust devils were identified in na and wa images and dust devil tracks were identified in na images great spatial variability in dust devil occurrence is highlighted with amazonis planitia being the most active region examined other active regions included cimmerium sinai and solis numerous dust devil tracks but very few dust devils were observed in casius this may suggest dust devils here occur at local times other than that of the mgs orbit 2 pm alternatively variations in surface properties may affect the ability of dust devils to leave visible tracks the seasonal campaign within amazonis shows a relatively smooth variation of dust devil activity with season peaking in mid northern summer and falling to zero in southern spring and summer this pattern of activity correlates well with the boundary layer maximum depth and hence the vigor of convection global maps of boundary layer depth and surface temperature do not predict that amazonis should be especially active potentially suggesting a role for mesoscale circulations measurement of observed dust devils yields heights of up to 8 km and widths in excess of 0 5 km

orbital monitoring of martian surface changes abstract a history of martian surface changes is documented by a sequence of global mosaics made up of mars global surveyor mars orbiter camera daily color images from 1999 to 2006 together with a single mosaic from the mars reconnaissance orbiter mars color imager in 2009 these observations show that changes in the global albedo patterns of mars take place by a combination of dust storms and strong winds many of the observed surface changes took place along the tracks of seasonally repeating winter dust storms cataloged by wang and richardson 2015 these storms tend to sweep dust towards the equator progressively shifting albedo boundaries and continuing surface changes that began before the arrival of mgs the largest and most conspicuous changes took place during the global dust storm of 2001 my 25 which blanketed syrtis major stripped dust from the tharsis region and injected dust into solis planum high wind speeds but low wind stresses are predicted in syrtis tharsis and solis by the nasa ames gcm frequent changes in these regions show that dust accumulations are quickly removed by stronger winds that are not predicted by the gcm but may result from smaller scale influences such as unresolved topography

recurring slope lineae in equatorial regions of mars the presence of liquid water is a requirement of habitability on a planet possible indicators of liquid surface water on mars include intermittent flow like features observed on sloping terrains these recurring slope lineae are narrow dark markings on steep slopes that appear and incrementally lengthen during warm seasons on low albedo surfaces the lineae fade in cooler seasons and recur over multiple mars years recurring slope lineae were initially reported to appear and lengthen at mid latitudes in the late southern spring and summer and are more common on equator facing slopes where and when the peak surface temperatures are higher here we report extensive activity of recurring slope lineae in equatorial regions of mars particularly in the deep canyons of valles marineris from analysis of data acquired by the mars reconnaissance orbiter we observe the lineae to be most active in seasons when the slopes often face the sun expected peak temperatures suggest that activity may not depend solely on temperature although the origin of the recurring slope lineae remains an open question our observations are consistent with intermittent flow of briny water such an origin suggests surprisingly abundant liquid water in some near surface equatorial regions of mars dark streaks that appear on the surface of mars during warm seasons have been observed at the mid latitudes and tentatively attributed to the flow of briny water imagery from the mars reconnaissance orbiter over multiple mars years suggests that these seasonally active features are also present in equatorial regions where liquid surface water is not expected

results from the mars global surveyor thermal emission spectrometer the thermal emission spectrometer spectra of low albedo surface materials suggests that a four to one mixture of pyroxene to plagioclase together with about a 35 percent dust component provides the best fit to the spectrum qualitative upper limits can be placed on the concentration of carbonates 10 percent olivine 10 percent clay minerals 20 percent and quartz 5 percent in the limited regions observed limb observations in the northern hemisphere reveal low lying dust hazes and detached water ice clouds at altitudes up to 55 kilometers at an aerocentric longitude of 224 degrees a major dust storm developed in the noachis terra region the south polar cap retreat was similar to that observed by viking

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

early views of the martian surface from the mars orbiter camera of mars global surveyor high resolution images of the martian surface at scales of a few meters show ubiquitous erosional and depositional eolian landforms dunes sandsheets and drifts are prevalent and exhibit a range of morphology composition inferred from albedo and age as seen in occurrences of different dune orientations at the same location steep walls of topographic depressions such as canyons valleys and impact craters show the martian crust to be stratified at scales of a few tens of meters the south polar layered terrain and superposed permanent ice cap display diverse surface textures that may reflect the complex interplay of volatile and non volatile components low resolution regional views of the planet provide synoptic observations of polar cap retreat condensate clouds and the lifecycle of local and regional dust storms

mars aerosol studies with the mgs tes emission phase function observations optical depths particle sizes and ice cloud types versus latitude and solar longitude 1 emission phase function epf observations taken in 1999 2001 by mars global surveyor thermal emission spectrometer mgs tes support the broadest study of martian aerosol properties to date tes solar band and infrared ir spectral epf sequences are analyzed to obtain first time seasonal latitudinal distributions of visible optical depths particle sizes and single scattering phase functions this combined angular and wavelength coverage enables identification of two distinct ice cloud types over 45 s 45 n type 1 ice clouds exhibit small particle sizes reff 1 2 m and a distinctive backscattering increase they are most prevalent in the southern hemisphere during aphelion but also appear more widely distributed in season and latitude as topographic and high altitude 20 km ice hazes type 2 ice clouds exhibit larger particle sizes reff 3 4 m a distinct side scattering minimum at 90 100 phase angles characteristic of a change in particle shape relative to the type 1 and appear most prominently in the northern subtropical aphelion cloud belt the majority of retrieved dust visible to ir optical depth ratios are indicative of reff 1 5 0 1 m consistent with pathfinder and viking mariner 9 reanalyses however increased ratios 2 7 versus 1 7 appear frequently in the northern hemisphere over ls 50 200 indicating substantially smaller dust particles sizes reff 1 0 0 2 m at this time in addition larger reff 1 8 2 5 m dust particles were observed locally in the southern hemisphere during the peak of the 2001 global dust storm detailed spectral modeling of the tes visible band pass indicates agreement of epf derived dust single scattering albedos 0 92 0 94 with the spectrally resolved results from pathfinder observations

a study of the possibility of sprites in the atmospheres of other planets 1 sprites are a spectacular type of transient luminous events which occur above thunderstorms immediately after lightning they have shapes of giant jellyfish carrots or columns and last tens of milliseconds in earth s atmosphere sprites mostly emit in red and blue wavelengths from excited n2 and n2 and span a vertical range between 50 and 90 km above the surface the emission spectra morphology and occurrence heights of sprites reflect the properties of the planetary atmosphere they inhabit and are related to the intensity of the initiating parent lightning this paper presents results of theoretical calculations of the expected occurrence heights of sprites above lightning discharges in the co2 atmosphere of venus the n2 atmosphere of titan and the h2 he atmosphere of jupiter the expected emission features are presented and the potential of detecting sprites in planetary atmospheres by orbiting spacecraft is discussed

relationship between frontal dust storms and transient eddy activity in the northern hemisphere of mars as observed by mars global surveyor we have compiled a catalog of frontal dust storms in the northern hemisphere using mars orbiter camera daily global maps spanning 2 3 martian years of mars global surveyor mgs observations from 1999 to 2003 the most vigorous frontal storms that flush dust to the low latitudes occur in early mid fall and mid late winter away from the northern winter solstice while many streaks are observed in the polar hood during the winter solstice period no frontal dust storms are observed in the vicinity of the north polar region we have also analyzed simultaneous mgs thermal emission spectrometer tes temperature data and found statistically significant negative temperature anomalies associated with frontal storms in the lowest scale height of the atmosphere the geographical and seasonal distributions of temperature standard deviations associated with transient variations agree well with the distributions of frontal storms the correlation deteriorates with increasing altitude suggesting that lower level temperature waves are associated with the frontal dust storms specifically eastward traveling m 3 waves with periods of 2 3 sols appear to be closely related to the development of flushing frontal storms

monitoring the perennial martian northern polar cap with mgs moc abstract we have used the mars global surveyor mars orbiter camera wide angle mgs moc wa dataset to study albedo trends on the martian northern residual cap six study regions were selected the chasma boreale source region three regions near the center of the cap fish hook region latitude 87 bottle opener region latitude 87 steep shallow region latitude 85 and two lower latitude regions crater latitude 77 and polar outlier latitude 82 and the albedos of these six regions were examined these regions were chosen due to their good temporal coverage in the moc dataset as well as having been studied by other researchers bass et al 2000 icarus 144 382 396 calvin and titus 2004 lunar planet sci xxxv abstract 1455 the picture which emerges is complex most areas experience a combination of darkening and brightening through the northern summer only one area consistently brightens the polar outlier region a good deal of interannual repeatability in each region s albedo behavior is seen however possible causes for the observed complex behaviors include dust deposition from late summer storms sintering of frost grains over the course of the summer and cold trapping of volatiles on bright cold surfaces

orbital change experiments with a mars general circulation model abstract we use a mars general circulation model to examine the effect of orbital changes on the planet s general circulation and climate system experiments are performed for obliquities ranging from 0 to 60 for two different longitudes of perihelion each experiment simulates a full mars year assuming a fixed atmospheric dust distribution and fixed amount of co 2 in the atmosphere cap system we find that global mean surface temperatures and pressures decline with increasing obliquity due to the increasing extent of the winter polar caps the seasonal co 2 cycle and intensity of the solstice circulation amplify considerably with increasing obliquity such that global dust storms are likely at both solstices the most significant feature of the high obliquity solstice circulations is the development of an intense low level jet associated with the return branch of the hadley circulation model surface stresses are used to map regions of preferred dust lifting which are defined in terms of an annual deflation potential for the present obliquity the model predicted regions of high deflation potential are in good agreement with cantor et al s 2001 j geophys res 106 23653 23688 observations which gives us some confidence in the model s ability to predict where lifting might occur when mars orbit parameters are different than they are today in general we find that the dust lifting potential increases sharply with obliquity and is greatest at times of high obliquity when perihelion coincides with northern summer solstice over an obliquity cycle the model global annual deflation potential ranges from several tenths of a millimeter at 0 obliquity to almost 15 mm at 60 obliquity much higher values are possible when the atmosphere is very dusty we find a strong correlation between the deflation potential and surface thermal inertia regions of high deflation potential correspond to regions of high thermal inertia high rock abundance and regions of low deflation potential correspond to regions of low thermal inertia high dust sand abundance furthermore while the regions of preferred lifting high deflation potential expand somewhat with increasing obliquity and dust loading the central parts of tharsis arabia and elysium show no tendency for significant lifting at any obliquity or longitude of perihelion these regions may therefore be very old and represent net long term sinks for atmospheric dust it is the topography of the planet through its influence on surface pressure and wind systems which ultimately determines where dust accumulates finally as was found by fenton and richardson 2001 j geophys res 106 32885 32909 we find no tendency for the development of east southeasterly winds at the pathfinder site for any of our orbital change experiments this suggests that the ancient wind regime discussed by greeley et al 2000 j geophys res 105 1829 1840 was produced by other factors such as polar wander

mesoscale linear streaks on mars environments of dust entrainment abstract variable surface albedo features on mars are likely caused by the entrainment and deposition of dust by the wind most discrete markings are associated with topographic forms or with regional slopes that serve to alter the effective wind shear stress on the surface some of the largest variable features here termed mesoscale linear streaks are up to 400 km in length and repeatedly occur in one of the smoothest regions of mars amazonis planitia their orientations and apparent season of variability as observed by viking and mars orbiter cameras indicate linear streak formation by enhanced surface wind stresses during regional or local dust storms and during the initial stages of global dust storms they provide an example of the ability of large scale winds without significant local enhancement to initiate dust motion on mars the sizes and spacing of the linear streaks may be controlled by boundary layer rolls the repetitive formation of these streaks over a span of more than 11 mars years gives one measure of the stability of mars eolian processes

winter and spring evolution of northern seasonal deposits on mars from omega on mars express the omega visible near infrared imaging spectrometer on mars express has observed the retreat of the northern seasonal deposits during martian year 27 28 from the period of maximum extension close to the northern winter solstice to the end of the retreat at l s 95 we present the temporal and spatial distributions of both co 2 and h 2o ices and propose a scenario that describes the winter and spring evolution of the northern seasonal deposits during winter the co 2 rich condensates are initially transparent and could be in slab form a water ice annulus surrounds the sublimating co 2 ice extending over 6 of latitude at l s 320 decreasing to 2 at l s 350 and gradually increasing to 4 5 at l s 50 this annulus first consists of thin frost as observed by the viking lander 2 and is then overlaid by h 2o grains trapped in the co 2 rich ice layer and released during co 2 sublimation by l s 50 h 2o ice spectrally dominates most of the deposits in order to hide the still several tens of centimeters thick co 2 ice layer in central areas of the cap we propose the buildup of an optically thick top layer of h 2o ice from ice grains previously embedded in the co 2 ice and by cold trapping of water vapor from the sublimating water ice annulus the co 2 ice signature locally reappears between l s 50 and 70 what emerges from our observations is a very active surface atmosphere water cycle these data provide additional constraints to the general circulation models simulating the martian climate copyright 2011 by the american geophysical union

north polar dust storms in early spring on mars abstract observations of mars during 1996 1997 by the hubble space telescope covered the entire spring season in the northern hemisphere of mars which was favorably positioned for viewing the north polar region this paper reports observations of dust activity during this period local dust activity occurred near the edge of the subliming north polar cap during early spring this included local dust clouds similar to those seen by viking near the edge of the south polar cap and unusual arc shaped dust features that seem to represent a new type of dust phenomenon these dust arcs may explain the rima tenuis rift which has been occasionally seen by groundbased observers of mars analysis of numerical simulations from a mars general circulation model for the early northern spring season have provided insights into the plausible meteorological background at high latitudes in the vicinity of the retreating north polar cap these hubble observations extend the geographic and seasonal ranges during which local dust activity seems to be common on mars the combination of image analysis and model calculations support the hypothesis that these dust storms are the result of winds associated with fronts moving across the seasonal cap that lift dust exposed on the cap during co 2 sublimation

mars orbiter camera observations of martian dust devils and their tracks september 1997 to january 2006 and evaluation of theoretical vortex models 1 a multiyear planet wide survey of martian dust devils was conducted using observations from mars global surveyor mars orbiter camera acquired through 21 january 2006 a total of 223 350 images were surveyed and 11 456 dust devils were seen in 0 4 of the images 11 5 in the southern and 88 5 in the northern hemisphere dust devils were observed at latitudes from 71 9 s to 62 2 n over a range of surface albedos am 0 11 0 22 and elevations from hellas 8750 m to arsia mons 17 250 m the light and dark toned streaks created by dust devils were observed from 80 s to 80 n and changed on timescales as short as 1 month at mid to high latitudes seasonal changes in streak patterns contribute to the seasonal wave of darkening observed telescopically from earth dust devils were observed in all seasons in both hemispheres with the exception of ls 202 8 281 5 in the north peak activity occurred during midsummer in each hemisphere five regions in amazonis syria claritas meridiani and gusev were monitored regularly amazonis had the largest dust devils and was the most active planet wide with annual activity occurring from ls 8 5 197 interannual variability resulted from dust storms and planet encircling dust hazes which were observed to initiate and abate dust devil activity there was no evidence suggesting dust devils cause or lead to initiation of dust storms model derived tangential wind speeds of large vortices were 20 m s 1 at 20 m above the surface dust flux calculations suggest that dust devils are a contributor to the background dust opacity observed through northern spring and summer

evidence of 210po on martian dust at meridiani planum 1 since the surveyor and apollo missions and up to the recent lunar prospector mission 222rn and 210po have been key isotopes for understanding gas release events and their spatial and temporal variations on the moon comparatively these isotopes have drawn much less attention on mars if any despite the wealth of information it could bring on the uppermost meters of the regolith the exchange of volatiles at the surface and the atmospheric aerosol cycle here we present a statistical analysis of the high energy end of alpha spectra obtained by the alpha particle x ray spectrometer onboard mars exploration rover opportunity and report evidence of 210po a decay product of 222rn attached to atmospheric dust the 210po surface activity on rocks and soils at the landing site is lower than 3 1 10 4 bq cm 2 but analysis of spectra obtained on the dust capture magnet reveals a 210po activity of 4 6 2 4 10 3 bq cm 2 2 this difference is due to the very low dust cover index at the landing site owing to frequent dust devils regional and global dust storms that mobilize substantial amounts of dust and homogenize the dust surface layer we infer that the global average 222rn exhalation rate is significantly greater on mars than on the moon this comparison supports the hypothesis that on mars radon emanation could be comparatively enhanced by the presence of water in the surficial soil analysis of atmospheric spectra yields a radon activity upper limit of 16 5 bq m 3 during nighttime at the landing site

context camera investigation on board the mars reconnaissance orbiter 1 the context camera ctx on the mars reconnaissance orbiter mro is a facility instrument i e government furnished equipment operated by a science team not responsible for design and fabrication designed built and operated by malin space science systems and the mro mars color imager team marci ctx will 1 provide context images for data acquired by other mro instruments 2 observe features of interest to nasa s mars exploration program e g candidate landing sites and 3 conduct a scientific investigation led by the marci team of geologic geomorphic and meteorological processes on mars ctx consists of a digital electronics assembly a 350 mm f 3 25 schmidt type telescope of catadioptric optical design with a 5 7 field of view providing a 30 km wide swath from 290 km altitude and a 5000 element ccd with a band pass of 500 700 nm and 7 m pixels giving 6 m pixel spatial resolution from mro s nearly circular nearly polar mapping orbit raw data are transferred to the mro spacecraft flight computer for processing e g data compression before transmission to earth the ground data system and operations are based on 9 years of mars global surveyor mars orbiter camera on orbit experience ctx has been allocated 12 of the total mro data return or about 3 terabits for the nominal mission this data volume would cover 9 of mars at 6 m pixel but overlapping images for stereo mosaics and observation of changes and meteorological events will reduce this area ctx acquired its first instrument checkout images of mars on 24 march 2006

the effects of martian orbital variations upon the sublimation and relaxation of north polar troughs and scarps abstract the north polar layered deposits pld of mars are climatologically significant because they represent the largest actively exchanging reservoir of martian water the kilometer scale topography of the north pld is dominated by troughs and scarps which exhibit highly correlated surface slopes and total depths the most widespread theories of pld evolution presume that the asymmetrical nature of north pld troughs characterized by equatorward facing slopes that are generally steeper than poleward facing slopes is the result of preferential h 2 o sublimation from equatorward facing trough walls however our orbitally modulated simulations indicate that there is no long term sublimation advantage of equatorward facing trough walls because of the effects of obliquity upon the slope dependence of sublimation rate in contrast we propose that viscous relaxation of subsurface water is consistent with the slope and depth distributions of north pld troughs and scarps the results of our finite element simulations suggest that a mere 2 k difference in the subsurface temperatures of opposing trough walls is sufficient to produce the observed slope disparity due to the slower rate of uplift of colder poleward facing trough walls both our sublimation and relaxation simulations indicate that present day north pld troughs have formed since 5 ma and are not sites of long term deposition additionally our results imply that glacial flow may govern the large scale evolution of the north pld especially at high obliquity

new criterion for sediment suspension and wind speed proxy in planetary atmospheres 1 sediment suspension is a common and important phenomenon in planetary atmospheres a widely used suspension criterion also a proxy boundary layer wind speed indicator was discredited by mars exploration rover mission results concerning sediment particle sizes in active surface bed forms parameterisation of a new dynamic suspension criterion based upon turbulent stress yields predicted suspension threshold conditions consistent with those inferred for earth and predicts no suspension of sand grade particles for recent martian wind velocities at 1m height estimated in the range 28 73 m s 1 results for venus imply suspension of very fine sand particles at low surface wind speeds

detection of northern hemisphere transient eddies at gale crater mars abstract the rover environmental monitoring station rems on the curiosity rover is operating in the southern hemisphere of mars and is detecting synoptic period oscillations in the pressure data that we attribute to northern hemisphere transient eddies we base this interpretation on the similarity in the periods of the eddies and their seasonal variations with those observed in northern midlatitudes by viking lander 2 vl 2 18 mars years earlier further support for this interpretation comes from global circulation modeling which shows similar behavior in the transient eddies at the grid points closest to curiosity and vl 2 these observations provide the first in situ evidence that the frontal systems often associated with flushing dust storms do cross the equator and extend into the southern hemisphere

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

curvilinear features in the southern hemisphere observed by mars global surveyor mars orbiter camera abstract we have used the complete set of mars global surveyor mgs mars daily global maps mdgms to study martian weather in the southern hemisphere focusing on curvilinear features including frontal events and streaks frontal events refer to visible events that are morphologically analogous to terrestrial baroclinic storms mdgms show that visible frontal events were mainly concentrated in the 210 300 e 60 150 w sector and the 0 60 e sector around the southern polar cap during l s 140 250 and l s 340 60 the non uniform spatial and temporal distributions of activity were also shown by mgs thermal emission spectrometer transient temperature variations near the surface streaks refer to long curvilinear features in the polar hood or over the polar cap they are an indicator of the shape of the polar vortex streaks in late winter usually show wavy segments between the 180 meridian and argyre model results suggest that the zonal wave number m 3 eastward traveling waves are important for their formation

low albedo surfaces and eolian sediment mars orbiter camera views of western arabia terra craters and wind streaks 1 high spatial resolution 1 5 to 6 m pixel mars global surveyor mars orbiter camera images obtained september 1997 to june 2001 show that each of the large dark wind streaks of western arabia terra originate at a barchan dune field on a crater floor the streaks consist of a relatively thin 1 m coating of sediment deflated from the dune fields and their vicinity in most cases this sediment drapes over a previous mantle that more thickly covers nearly all of western arabia terra no concurrent eolian bedforms are found within the dark streaks nor do any dunes climb up crater walls to deliver sand via saltation to the streaks the relations between dunes wind streak and subjacent terrain imply that dark toned grains finer than those that comprise the dunes are lifted into suspension and carried out of the craters to be deposited on the adjacent terrain previous eolian physics and thermal inertia studies suggest that under modern martian conditions such grains likely include silt 3 9 62 5 m very fine sand 62 5 125 m and possibly fine sand to 210 m the streaks change in terms of extent relative albedo and surface pattern over periods measured in years however through june 2001 very little evidence for recent eolian activity dust plumes storms dune movement was observed

a local dust storm in the chryse region of mars viking orbiter observations a local dust storm was observed near the viking lander 1 site by viking orbiter l in september 1977 when the areocentric longitude of the sun ls was 340 shortly before vernal equinox the orbiter observations which consisted of a time sequence of pictures show that the storm moved at about 50 m sec to the ene from the lunae planum region into the chryse basin both baroclinic waves and topography may have been associated with the generation of the storm

a multi year survey of dynamics near the surface in the northern hemisphere of mars short period baroclinic waves and dust storms abstract baroclinic waves figure prominently in the dynamics of the northern hemisphere of mars and extensive observations by the viking landers and two atmospheric sounders on mars global surveyor have revealed many of their basic properties however previous investigations considered these data sets individually so that their cumulative value is not fully appreciated we have re examined these data to extract new information about the dynamics near the surface at mid to high northern latitudes by applying the same method of spectral analysis to each type of observation we derive a uniform multi year characterization of basic elements of martian weather this survey documents the time evolution of baroclinic waves among modes with different periods and zonal wave numbers we devote particular attention to a recurring wave 3 mode which is distinguished by its capacity to initiate regional dust storms in the topographic basins of the northern hemisphere our results include a detailed case study that shows how the intermittence of this mode and the strong zonal modulation of its amplitude influence the timing and location of these distinctive flushing dust storms more generally we find that the properties of the wave 3 mode are largely the same whenever it appears and that its intermittence plays an important role in the annual dust cycle

orographic control of storm zones on mars low pressure cyclones and their accompanying frontal systems in the middle latitudes of the earth s troposphere develop travel eastwards and decay preferentially within latitudinally and longitudinally confined geographical regions known as storm zones1 these zones can be readily identified in the circulation statistics of terrestrial weather systems2 mars like the earth is a rapidly rotating solid planet and has a seasonally varying shallow atmosphere large scale orography and in a broadly defined context continental structures3 although there are also important differences between the two planets travelling weather systems do exist on mars3 this raises the question of whether storm zones also occur there and if so by what mechanisms here we report the results of numerical simulations of global atmospheric circulation patterns on mars we find that storm zones can exist during the northern winter and that continental scale orography rather than surface thermal contrasts is the main factor determining the development of these zones storm zones on mars should play an important role in the martian climate cycle4 5 by influencing the transport of for example heat momentum water vapour and atmospheric dust3 6 8 towards the poles

quasi periodic dust events in the summertime south polar region of mars abstract a hovmoller diagram analysis of the dust optical depth measured by the mars global surveyor thermal emission spectrometer shows the occurrence of quasi periodic westwardly propagating disturbances with timescales of 10 20 sols during summer in the south polar region of mars dust clouds emerge repeatedly around the region with a latitude of around 70 80 s and a longitude of 240 300 e move westward at speeds of 3 6 m s 1 reach the region with a longitude of 60 120 e and finally disappear this longitude range coincides with elevated terrains in the south polar region and in this region an increase of dust optical depth encircling the south pole is also observed this implies that the quasi periodic dust events will contribute to the enhancement of the atmospheric dust loading in this region these dust events might be related to baroclinic instability caused by the thermal contrast across the co2 cap edge or the horizontal advection or vertical convection with radiative dynamical feedback the westward movement of the dust clouds suggests steady westward winds blowing in the near surface layer where the quasi periodic dust lifting is expected to occur such a westward cap edge flow will be created by the coriolis force acting on the flow from the ice side to the regolith side

daily and seasonal viking observations of martian bore wave systems a martian atmospheric phenomenon called a bore wave has been observed by the viking imaging system during late spring and early summer of two martian years in the tharsis ridge region of the planet the observational data are presented and a tentative explanation is offered for the occurrence of this feature formed by airflow and which behaves like a thermally induced diurnal katabatic breeze

geologic context of recurring slope lineae in melas and coprates chasmata mars one of the major mars discoveries of recent years is the existence of recurring slope lineae rsl which suggests that liquid water occurs on or near the surface of mars today these dark and narrow features emerge from steep rocky exposures and incrementally grow fade and reform on a seasonal basis and are detected in images from the high resolution imaging science experiment camera rsl are known to occur at scattered midlatitude and equatorial sites with little spatial connection to one another one major exception is the steep low albedo slopes of melas and coprates chasmata in valles marineris where rsl are detected among diverse geologic surfaces e g bedrock and talus and landforms e g inselbergs and landslides new images show topographic changes including sediment deposition on active rsl slopes midwall locations in coprates and melas appear to have more areally extensively abundant rsl and related fans as compared with other rsl sites found on mars water budget estimates for regional rsl are on the order of 105 to 106 m3 of fluid for depths of 10 to 100 mm and suggest that a significant amount of near surface water might be present many rsl are concentrated near local topographic highs such as ridge crests or peaks which is challenging to explain via groundwater or ice without a recharge mechanism collectively results provide additional support for the notion that significant amounts of near surface water can be found on mars today and suggest that a widespread mechanism possibly related to the atmosphere is recharging rsl sources

formation and erosion of layered materials geologic and dust cycle history of eastern arabia terra mars 1 eastern arabia terra is mantled in a layer of dust a few centimeters to a meter thick yet contains morphologic features that suggest a history of multiple events of deposition and consolidation of fine grained material and a significant amount of erosion early in martian history this region was affected by volcanic and fluvial activity but has since been dominated by aeolian processes five craters in this region contain interior mound material that ranges in height from 1600 to 2100 m above the crater floor the fluted erosional pattern and the thermal inertia are suggestive of a weakly indurated material and the extensive layering implies that these mounds were formed by a repeated process or processes although these materials primarily occur within craters there are materials outside craters that have similar erosional features and fine laminations suggesting a more extensive deposit the most likely process to form this material is the deposition and cementation of air fall dust and is potentially related to martian obliquity changes the significant amount of erosion of the intracrater mounds unit indicates a dramatic change from a depositional environment to an erosional regime over the past 106 108 years currently dust is accumulating in this region in years with planet encircling dust events but global circulation model results indicate that dust devils may be removing slight amounts of dust from arabia terra these observations suggest that the thickness of the dust mantle may not be currently increasing and may instead be in equilibrium

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

long term wind erosion on mars abstract wind erosion and deposition are powerful agents of surface change on mars erosion is sensitive to the atmospheric density so feedback between orbit variations and atmospheric density can enhance the sensitivity of erosion rates to orbital parameters we use statistics derived from a 1 gyr integration of the spin axis of mars coupled with runs of the nasa ames 3 d general circulation model gcm at a variety of orbital conditions and pressures to explore this feedback we find that wind erosion in the gcm is associated with two factors baroclinic zone winds and strong cross equator solstice flows both of these factors are influenced by topography producing an asymmetry in the erosion pattern between the north and the south the erosion model averaged over 1 gyr produces potential erosion rates of 1 7 10 5 m yr 1 in the north and 1 0 10 5 m yr 1 in the south which increase by an order of magnitude in an early 28 mbar atmosphere the stability of these potential erosion patterns over geological time indicates that the lowland regions of mars are continuously eroded and that wind is capable of revealing ancient sedimentary deposits or eroding substantial deposits that may have otherwise been preserved

the seasonal behavior of water ice clouds in the tharsis and valles marineris regions of mars mars orbiter camera observations abstract the mars global surveyor mars orbiter camera was used to obtain global maps of the martian surface with equatorial resolution of 7 5 km pixel in two wavelength ranges blue 400 450 nm and red 575 625 nm the maps used were acquired between march 15 1999 ls 110 and july 31 2001 ls 205 corresponding to approximately one and a quarter martian years using the global maps cloud area in km2 has been measured daily for water ice clouds topographically corresponding to olympus mons ascraeus mons pavonis mons arsia mons alba patera the western valles marineris canyon system and for other small surface features in the region seasonal trends in cloud activity have been established for the three tharsis volcanoes olympus mons and alba patera olympus ascraeus and pavonis mons show cloud activity from about ls 0 220 with a peak in cloud area near ls 100 one of our most interesting observational results is that alba patera shows a double peaked feature in the cloud area with peaks at ls 60 and 140 and a minimum near ls 100 arsia mons shows nearly continuous cloud activity the altitudes of several of these clouds have been determined from the locations of the visual cloud tops and optical depths were measured for a number of them using the disort code of stamnes et al 1988 appl opt 27 2502 2509 several aspects of the observations e g cloud heights effects of increased dust on cloud activity are similar to simulations in richardson et al 2002 j geophys res 107 5064 a search for short period variations in the cloud areas revealed only indirect evidence for the diurnal cloud variability in the afternoon hours unambiguous evidence for other periodicities was not found

evidence for indurated sand dunes in the martian north polar region 1 we investigate the relevance of induration as an explanation for the occurrence of dunes of unusual morphology in the martian north polar region the evidence for induration of aeolian deposits on mars is reviewed an explanation for rounded elongated barchans in chasma boreale is presented the role played by induration in the formation of linear dunes is discussed our arguments are supported by the results of a computer simulation model

martian dust storms 1999 mars orbiter camera observations the mars orbiter camera on board the mars global surveyor from march 9 1999 ls 107 where ls is the areocentric longitude of the sun measured in degrees from mars northern spring equinox to december 31 1999 ls 274 has obtained 7 5 km pixel 1 daily global maps of the martian surface in two wavelength bands blue 400 450 nm and red 575 625 nm visual inspection of these maps during the 1999 dust storm season has resulted in the detection of 783 dust storms ranging in size from local 102 km2 to regional 1 6 106 km2 no global storms were observed the difference in the numbers of dust storms occurring in the two hemispheres north 343 south 440 was not statistically significant fifty percent of the regional size dust storms formed as a result of the merger of two or more smaller local storms the regional storms from ls 207 to ls 223 were observed to move from the northern hemisphere into the southern hemisphere between 30 w and 50 w longitude this cross equatorial transport of dust suggests the location of the low lying southward flowing branch of the hadley circulation observations show that dust storms occur in several regions on mars at the two polar cap edges at the base of high elevation regions in the northern hemisphere near the polar hood during northern fall and at mid latitudes in both hemispheres specific regions such as solis planum and hesperia which were regions of significant dust activity in the past showed almost no dust storm activity in 1999 suggesting that regional dust sources are variable over a 20 year time frame one region of exceptional activity not noted previously was the arcadia amazonis border however other regions such as near elysium mons acidalia chryse hellas noachis argyre cimmeria and sirenum again were active dust storm regions relative dust opacities were modeled for 117 red wavelength events and ranged from 0 54 diffuse haze to 2 13 concentrated local events from the dust opacities we estimated the north polar sedimentation rate to be 6 0 10 10 4 g cm 2 yr 1 a factor of 40 smaller than previous estimates from the two 1977 global dust storms pollack et al 1979 along with the global dust mass loading 2 6 4 0 10 4 g cm 2 and cross equatorial dust mass loading 3 6 10 4 g cm 2 the 1999 cross equatorial mass dust loading suggests that the southern hemisphere subtropical latitudes require at least 2 3 martian years to replenish their dust sources before global storms can form

low frequency variability of the indian monsoon enso relationship and the tropical atlantic the weakening of the 1980s and 1990s abstract the indian monsoon el nino southern oscillation enso relationship according to which a drier than normal monsoon season precedes peak el nino conditions weakened significantly during the last two decades of the twentieth century in this work an ensemble of integrations of an atmospheric general circulation model agcm coupled to an ocean model in the indian basin and forced with observed sea surface temperatures ssts elsewhere is used to investigate the causes of such a weakening the observed interdecadal variability of the enso monsoon relationship during the period 1950 99 is realistically simulated by the model and a dominant portion of the variability is associated with changes in the tropical atlantic ssts in boreal summer in correspondence to enso the tropical atlantic ssts display negative anomalies south of the equator in the last quarter of the twentieth century and weakly positive anomalies in the previous period those anomalies in turn produce heating anomalies which excit

topographic control of hydrogen deposits at low latitudes to midlatitudes of mars 1 correlations between the longitudinal wave number two distribution of water equivalent hydrogen weh at low latitudes to midlatitudes of mars with variations in topography surface albedo thermal inertia regional dust storms and atmospheric water vapor are explored to provide guidance in determining the mechanisms that recharge or maintain these weh reservoirs the closest match is with low thermal inertia coupled with orographic control of the present day atmospheric circulation dynamics the engine for the simulated longitudinal two wave pattern maxima in arabia and tharsis is relatively cold nighttime surface temperatures and large amplitude temperature inversions that concentrate water ice over these regions geologically recent precipitated water ice by itself is insufficient to account for the observed distribution of weh retention of precipitate by hydratable minerals is necessary while current research cannot presently identify the hydration mechanism for the weh distribution whether it be from a past obliquity present climate conditions or some convolution of both this research suggests that current climatic conditions can sustain if not emplace the observed longitudinally constrained distribution of equatorial weh

analysing some martian atmospheric characteristics associated with a dust storm over the lunae planum region during october 2014 abstract this study analyses the vertical aerosol distribution and associated atmospheric characteristics during a dust storm event in early martian southern summer the analysis is based on the observations of the mars colour camera mcc onboard the indian mars orbiter mission during october 11 and october 20 2014 a local scale dust storm is found within the north eastern portion of the lunae planum region on october 11 2014 which is observed to be relatively larger during october 20 the dust storm disappeared in the next image taken over the same region during october 28 2014 leaving a thick haze over lunae planum and the valles marineris region it is observed from the mars daily global maps of the mars color imager marci on board the mars reconnaissance orbiter mro that the dust storm was generated in the acidalia region moved south and came over lunae planum and tempe terra later on this northern hemispheric storm sequence crossed the equator and merged with a hellas sequence over noachis terra an increase in vertically integrated dust opacity derived from the observations of mars climate sounder on board mro was seen over a large latitudinal extent i e 60 s to 60 n analysis of dust and water ice opacity and temperature profile is carried out before during and after the dust storm period as observed by mcc and marci images dust opacity is found to have increased drastically up to 20 km altitude an increase of dustiness at the hatdm high altitude tropical dust maximum layer is seen but with a temporal delay of 2 ls after the dust storm disappearance the study implicates the variation of convective boundary layer growth in the tenuous martian atmosphere during the dust storm scenario for this temporal delay in dust lifting the dust lifting is found to be exclusively responsible for the increase in heating rate at this layer not cloud radiative heating caused by water ice clouds

persistent dust cloud activity on mars near echus chasma in 1978 abstract clouds were recorded by viking cameras during five out of six observations over the same side canyon of echus chasma during a period of over 3 1 2 months in 1978 although these clouds were different from one another in appearance all were bright through a red filter and are believed to be at least partially composed of dust two of them were also imaged in violet light in which they were also bright therefore they may also have contained condensate a plausible explanation for the formation of the dust clouds is drainage winds which are also known to be active to the west in the tharsis region during this season in this case winds may have been flowing downslope from the north rim of tithonium chasma

the future of failure stress or strain abstract strains in rocks can be observed but ancient stresses can only be inferred we should re examine the potential of strain geometry as the key to understanding and interpreting common shear structures ranging from faults to plastic shear zones the concept of failure along zero extension directions can be applied to natural structures in rocks and is predicated on strain compatibility between differently strained volumes zero extension directions are considered for two strain configurations plane strain k 1 and uniaxial shortening k 0 the crucial difference between shear fractures or faults and plastic yield zones is that the former are preceded by dilatation while the latter are isovolumetric volume changes during deformation affect the orientations of zero extension directions and hence of the resulting structures with isovolumetric strain yield occurs on planes at 45 to the principal shortening direction in plane strain and at 54 7 to this axis in uniaxial shortening uniaxial shortening experiments on rock samples allow estimation of the relative volumetric strains when yield zones initiate when this volumetric strain is used to estimate the orientation of shear fractures in plane strain ca 70 dips are predicted for normal faults at high crustal levels decreasing downwards to 45

simulation of the atmospheric thermal circulation of a martian volcano using a mesoscale numerical model mesoscale 100 km atmospheric phenomena are ubiquitous on mars as revealed by mars orbiter camera images numerical models provide an important means of investigating martian atmospheric dynamics for which data availability is limited but the resolution of general circulation models which are traditionally used for such research is not sufficient to resolve mesoscale phenomena to provide better understanding of these relatively small scale phenomena mesoscale models have recently been introduced here we simulate the mesoscale spiral dust cloud observed over the caldera of the volcano arsia mons by using the mars regional atmospheric modelling system our simulation uses a hierarchy of nested models with grid sizes ranging from 240 km to 3 km and reveals that the dust cloud is an indicator of a greater but optically thin thermal circulation that reaches heights of up to 30 km and transports dust horizontally over thousands of kilometres

recent formation and evolution of northern martian polar layered deposits as inferred from a global climate model 1 we present a time marching model which simulates the exchange of water ice between the martian northern cap the tropics and a high latitude surface reservoir net annual exchange rates of water and their sensitivity to variations in orbital rotational parameters are examined using the martian water cycle modeled by the lmd three dimensional global climate model these rates are propagated over the last 10 myr to follow the thickness of the reservoirs the effect of a sublimation dust lag is taken account to test simple models of layer formation periods of high mean polar summer insolation 5 10 ma ago lead to a rapid exhaustion of a northern polar cap and a prolonged formation of tropical glaciers the formation of a northern cap and of a high latitude icy mantle may have started 4 ma ago with the average decrease of polar insolation tropical ice may have disappeared around 2 7 ma ago but small glaciers could have formed during the last peaks of polar summer insolation over the last 4 myr most of the present cap may have formed at the expense of tropical and high latitude reservoirs forming distinct layers at almost each 51 kyr 120 kyr insolation cycle layers thickness ranges from 10 to 80 m variations being produced by the modulation of the obliquity with 2 4 and 1 3 myr periods because only 30 insolation cycles have occurred since 4 ma ago we found an inconsistency between the recent astronomical forcing the observed number of layers and simple astronomically based scenarios of layers formation

the global topography of mars and implications for surface evolution elevations measured by the mars orbiter laser altimeter have yielded a high accuracy global map of the topography of mars dominant features include the low northern hemisphere the tharsis province and the hellas impact basin the northern hemisphere depression is primarily a long wavelength effect that has been shaped by an internal mechanism the topography of tharsis consists of two broad rises material excavated from hellas contributes to the high elevation of the southern hemisphere and to the scarp along the hemispheric boundary the present topography has three major drainage centers with the northern lowlands being the largest the two polar cap volumes yield an upper limit of the present surface water inventory of 3 2 to 4 7 million cubic kilometers

mass movement within a slope streak on mars 1 slope streaks on mars represent a currently active geological process various theories for slope streak formation have suggested that slope streaks form by disturbing only a thin surface veneer or by staining of the surface preserving pre existing topography within the streak theories also vary as to whether the formation mechanism requires the presence of water or another liquid we present observations of a slope streak that reveal topographic mounds within the streak these mounds do not continue outside the streak and we suggest that they formed with or immediately after the slope streak we use estimates of the total volume of mounds in this particular streak compared with the estimated excavation volume to extrapolate to a global sediment transport rate from slope streak formation if this slope streak is typical then this calculated rate is greater than estimates of the total volume of material transported by dust storms each year

mars observer camera the mars observer camera moc is a three component system one narrow angle and two wide angle cameras designed to take high spatial resolution pictures of the surface of mars and to obtain lower spatial resolution synoptic coverage of the planet s surface and atmosphere the cameras are based on the push broom technique that is they do not take frames but rather build pictures one line at a time as the spacecraft moves around the planet in its orbit moc is primarily a telescope for taking extremely high resolution pictures of selected locations on mars using the narrow angle camera areas ranging from 2 8 km 2 8 km to 2 8 km 25 2 km depending on available internal digital buffer memory can be photographed at about 1 4 m pixel additionally lower resolution pictures to a lowest resolution of about 11 m pixel can be acquired by pixel averaging these images can be much longer ranging up to 2 8 500 km at 11 m pixel high resolution data will be used to study sediments and sedimentary processes polar processes and deposits volcanism and other geologic geomorphic processes the moc wide angle cameras are capable of viewing mars from horizon to horizon and are designed for low resolution global and intermediate resolution regional studies low resolution observations can be made every orbit so that in a single 24 hour period a complete global picture of the planet can be assembled at a resolution of at least 7 5 km pixel regional areas covering hundreds of kilometers on a side may be photographed at a resolution of better than 250 m pixel at the nadir such images will be particularly useful in studying time variable features such as lee clouds the polar cap edge and wind streaks as well as acquiring stereoscopic coverage of areas of geological interest the limb can be imaged at a vertical and along track resolution of better than 1 5 km different color filters within the two wide angle cameras permit color images of the surface and atmosphere to be made to distinguish between clouds and the ground and between clouds of different composition

aeolian processes as drivers of landform evolution at the south pole of mars abstract we combine observations of surface morphology topography subsurface stratigraphy and near surface clouds with mesoscale simulations of south polar winds and temperature to investigate processes governing the evolution of spiral troughs on the south pole of mars in general we find that the south polar troughs are cyclic steps that all formed during an erosional period contrary to the troughs at the north pole which are constructional features the shallow radar instrument sharad onboard mars reconnaissance orbiter detects subsurface stratigraphy indicating relatively recent accumulation that occurred post trough formation in many locations using optical instruments especially the thermal emission imaging system themis we find low altitude trough clouds in over 500 images spanning 6 mars years the locations of detected clouds correspond to where recent accumulation is detected by sharad and offers clues about surface evolution the clouds migrate by season moving poleward from 71 s at l s 200 until l s 318 when the last cloud is detected our atmospheric simulations find that the fastest winds on the pole are found roughly near the external boundary of the seasonal co 2 ice cap thus we find that the migration of clouds and katabatic jumps corresponds spatially to the retreat of the co 2 seasonal ice as detected by titus 2005 and that trough morphology through recent accumulation is integrally related to this seasonal retreat

further observations of regional dust storms and baroclinic eddies in the northern hemisphere of mars abstract we have investigated the near surface meteorology in the northern hemisphere of mars through detailed analysis of data obtained with mars global surveyor in january august 2005 the season in the northern hemisphere ranged from midsummer through winter solstice of mars year my 27 we examined composite wide angle images from the mars orbiter camera and compiled a catalog of the dust storms that occurred in this interval as in previous martian years activity in the northern hemisphere was dominated by regional flushing dust storms that sweep southward through the major topographic basins most frequently in acidalia planitia we also used atmospheric profiles retrieved from radio occultation experiments to characterize eddy activity near the surface at high northern latitudes there are strong correlations between the two sets of observations which allowed us to identify three factors that influence the timing and location of the regional dust storms 1 transitions among baroclinic wave modes which strongly modulate the intensity of meridional winds near the surface 2 storms zones which impose strong zonal variations on the amplitude of some baroclinic eddies and 3 stationary waves which further modulate the wind field near the surface the flushing dust storms ceased abruptly in midautumn possibly in response to source depletion co 2 condensation a shift in the period of the baroclinic eddies and changes in the tidal wind field near the surface our results extend the meteorological record of the northern hemisphere substantiate the findings of previous investigations and further illuminate the climatic impact of baroclinic eddies