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

south polar residual cap of mars features stratigraphy and changes abstract the south residual polar cap of mars rich in co2 ice is compositionally distinct from the north residual cap which is dominantly h2o ice the south cap is also morphologically distinct displaying a bewildering variety of depressions formed in thin layered deposits which have been observed to change by scarp retreat over an interval of one mars year malin et al 2001 science 294 2146 2148 the climatically sensitive locale of the residual caps suggests that their behavior may help in the interpretation of recent fluctuations or repeatability of the mars climate we have used mars global surveyor mars orbiter camera moc images obtained in three southern summers to map the variety of features in the south residual cap and to evaluate changes over two mars years mars y the images show that there are two distinct layered units which were deposited at different times separated by a period of degradation the older unit 10 m thick has layers approximately 2 m thick the younger unit has variable numbers of layers each 1 m thick the older unit is eroding by scarp retreat averaging 3 6 m mars y a rate greater than the retreat of 2 2 m mars y observed for the younger unit the rates of scarp retreat and sizes of the different types of depressions indicate that the history of the residual cap has been short periods of deposition interspersed with longer erosional periods erosion of the older unit probably occupied 100 150 mars y one layer may have been deposited after the mariner 9 observations in 1972 residual cap layers appear to differ from normal annual winter deposits by having a higher albedo and perhaps by having higher porosities these properties might be produced by differences in the depositional meteorology that affect the fraction of high porosity snow included in the winter deposition

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

an observational overview of dusty deep convection in martian dust storms abstractdeep convection as used in meteorology refers to the rapid ascent of air parcels in earth s troposphere driven by the buoyancy generated by phase change in water deep convection undergir

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

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

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

numerical simulation of the winter polar wave clouds observed by mars global surveyor mars orbiter laser altimeter abstract in 1998 the mars orbiter laser altimeter revealed the presence of isolated or quasi periodic thick clouds during the martian polar night they are believed to be composed of co 2 ice particles and to be tilted against the wind direction a feature characteristic of vertically propagating orographic gravity waves to support that interpretation we present here numerical simulations with a two dimensional anelastic model of stratified shear flow that includes simple co 2 ice microphysics in some of the simulations presented the orography is an idealized trough with dimensions characteristic of the many troughs that shape the mars polar cap in others it is near the real orography in the polar night conditions our model shows that gravity waves over the north polar cap are strong enough to induce adiabatic cooling below the co 2 frost point from this cooling airborne heterogeneous nucleation of co 2 ice particles occurs from the ground up to the altitude of the polar thermal inversion although the model predicts that clouds can be present above 15 km only low altitude clouds can backscatter the laser beams of mola at a detectable level accordingly the shape of the laser echoes is related to the shape of the clouds at low level but do not necessarily coincide with the top of the clouds the model helps to interpret the cloud patterns observed by mola above an isolated orographic trough an isolated extended sloping cloud tilted against the wind is obtained the model shows that the observed quasi periodic clouds are due to the succession of small scale topographic features rather than to the presence of resonant trapped lee waves indeed the co 2 condensation greatly damps the buoyancy force essential for the maintenance of gravity waves far from their sources simulations with realistic topography profiles show the cloud response is sensitive to the wind direction when the wind is directed upslope of the polar cap on the one hand a large scale cloud modulated by small scale waves forms just above the ground on the other hand when the wind is directed downslope air is globally warmed and periodic ice clouds induced by small scale orography form at altitudes higher than 3 5 km above the ground in both cases a good agreement between the simulated echoes and the observed one is obtained according to our model we conclude that the observed clouds are quasi stationary clouds made of moving ice particles that successively grow and sublimate by crossing cold and warm phases of orographic gravity waves generated by the successive polar troughs we also find that the rate of ice precipitation is relatively weak except when there is a large scale air dynamical cooling

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

the conrad rise as an obstruction to the antarctic circumpolar current the antarctic circumpolar current acc carries water freely around the whole continent of antarctica but not without obstructions some such as the drake passage constrict its path while others such as mid ocean ridges may induce meandering in the current s cores and may cause the genesis of mesoscale turbulence it has recently been demonstrated that some regions that are only relatively shallow may also have a major effect on the flow patterns of the acc this is here shown to be particularly true for the conrad rise using the trajectories of surface drifters altimetry and the simulated velocities from a numerical model we show that the acc bifurcates at the western side of this rise in this process it forms two intense jets at the two meridional extremities of the rise with a relatively stagnant water body over the rise itself preliminary results from a recent cruise provide compelling support for this portrayal

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

identifying martian atmospheric instabilities and their physical origins using bred vectors the bred vector bv technique applied to the geophysical fluid dynamics laboratory gfdl mars general circulation model mgcm identifies regions and seasons of instability of the martian atmosphere and a kinetic energy equation applied to the control and perturbed states elucidates their physical origins instabilities prominent in the late autumn to early spring seasons of each hemisphere along the polar temperature front result from baroclinic conversions from bv potential to bv kinetic energy near the surface whereas both baroclinic and barotropic conversions play a role for the westerly jets aloft the low level tropics and the northern hemisphere summer are relatively stable with negative bred vector growth rates bred vector growth precedes initiation of travelling wave activity in the midlatitudes during the transition seasons and their structure relates to the eddy field topography plays a role in determining favoured locations for near surface instabilities bred vectors are also linked to forecast ensemble spread in data assimilation and help explain the growth of forecast errors we finally note that the ability to use breeding to identify instabilities as well as their physical origin depends on the fact that both the control and the perturbed solutions that give rise to bred vectors satisfy exactly the model s governing equations as a result this approach can be used with any dynamical system represented by a model copyright 2012 royal meteorological society

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

martian dust devil statistics from high resolution large eddy simulations dust devils are one of the key elements in the martian atmospheric circulation in order to examine their statistics we conducted high resolution up to 5 m and wide domain about 20 20 km2 large eddy simulations of the martian daytime convective layer large numbers of dust devils developed spontaneously in the simulations which enabled us to represent a quantitative consideration of martian dust devil frequency distributions we clarify the distributions of size and intensity a topic of debate and conclude that the maximum vertical vorticity of an individual dust devil has an exponential distribution while the radius and circulation have power law distributions a grid refinement experiment shows that the rate parameter of the vorticity distribution and the exponent of the circulation distribution are robust the mode of the size distribution depends on the resolution and it is suggested that the mode is less than 5 m

statistical biases and errors inherent in photoclinometric surface slope estimation with natural light photoclinometry is the most common method used to obtain high resolution topographic maps of planetary terrain we derive the likelihood function of photoclinometric surface slope from 1 the probability distribution of the measured photon count of natural sunlight through a charge coupled device ccd including uncertainty due to camera shot noise camera read noise small scale albedo fluctuation and atmospheric haze and 2 a photometric model relating photocount to surface orientation we then use classical estimation theory to determine the theoretically exact biases and errors inherent in photoclinometric surface slope and show when they may be approximated by asymptotic expressions for sufficiently high sample size we show how small scale albedo variability often dominates biases and errors which may become an order of magnitude larger than surface slopes when surface reflectance has a weak dependence on surface tilt we provide bounds on the minimum possible error of any unbiased photoclinometric surface slope estimate and compute the sample sizes necessary to constrain errors within desired design thresholds

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

two mars years of clouds detected by the mars orbiter laser altimeter 1 the mars orbiter laser altimeter mola instrument operated as an atmospheric lidar system as well as an altimeter detecting absorptive clouds in northern latitudes shortly after orbit insertion in october 1997 and reflective clouds over the north polar cap at the start of the science phasing orbits in march 1998 global cloud measurements commenced with the primary mapping mission in march 1999 with nearly continuous coverage for 1 25 mars years mola tracked several dust storms culminating with a major dust storm in june 2001 reflective clouds exhibiting distinctive patterns governed by insolation and the dynamics of the atmosphere were detected at elevations up to 20 km above the surface chiefly in the polar winter night mola distinguishes cloud returns by pulse width and energy measurements unusually strong and brief reflections with minimal extinction suggest precipitation of co2 snow under supercooled conditions weaker cloud reflections occurred at all latitudes some reflective daylight clouds at low latitudes suggested convective vortices or dust devils ground fogs composed of dust and h2o ice formed at night along the seasonal frost line absorptive clouds while not resolved altimetrically tracked the advancing and receding edges of the seasonal polar caps the absorptive and reflective clouds provide a seasonal profile of atmospheric activity spanning two martian years winter reflective cloud activity declined to background levels earlier in the second year at both poles suggesting interannual warming

martian north polar cap recession 2000 mars orbiter camera observations abstract the wide angle cameras of the mars orbiter camera moc on the mars global surveyor have recorded the 2000 recession of the seasonal co 2 cap in the north polar region from l s 330 to 90 in stark contrast to the asymmetric behavior of the south seasonal cap the seasonal north cap remains relatively circular and uniform until mid spring when the retreat reaches the circum polar dune field which is the one major nonuniformity in the cap the recession of cap edge latitude versus areocentric longitude l s is very well represented as a linear function until late spring there is no evidence for the plateau or standstill in the recession curve that has been observed in some prior years the lambert albedo of the seasonal frost deposits in the north polar region demonstrates the increase with insolation first observed by paige in 1985 increasing to approximately 0 57 at l s 40 the north polar cap near solstice visually appears smaller than that observed by moc at the start of mapping in 1999 but later images acquired in summer show the residual cap returning to its more usual shape the most likely explanation for these changes in albedo is precipitation and subsequent removal of dust on the cap as a result of frequent dust storms near the cap edge

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 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

marci and moc observations of the atmosphere and surface cap in the north polar region of mars abstract we used mgs moc and mro marci daily mapping images of the north polar region of mars from 16 august 2005 ls 270 to 21 may 2009 ls 270 covering portions of three consecutive martian years my 27 my 29 to observe the seasonal behavior of the polar ice cap and atmospheric phenomena the rate of cap regression was similar in my 28 and my 29 but was advanced by 3 5 of ls 7 8 sols in my 29 the spatial and temporal behaviors of dust and condensate clouds were similar in the two years and generally in accord with prior years dust storms 100 km2 were observed in all seasons with peak activity occurring at ls 10 20 from 50 n to 70 n and at ls 135 140 from 70 n to 90 n the most active quadrant was 0 90 w in my 28 shifting to 180 270 w in my 29 the majority of regional storms in both years developed in longitudes from 10 w to 60 w during late summer the larger storms obscure the north polar region in a cloud of dust that transitions to north polar hood condensate clouds around autumnal equinox changes in the distribution of perennial ice deposits especially in olympia planum were observed between the 2 years with the my 29 ice distribution being the most extensive observed to date modeling suggests that the small bright ice patches on the residual cap are not the result of slope or elevation effects rather we suggest that they are the result of local meteorological effects on ice deposition the annual darkening and brightening of peripheral areas of the residual cap around summer solstice can be explained by the sublimation of a brighter frost layer revealing an underlying darker ice rich layer that itself either sublimes to reveal brighter material below or acts as a cold trap attracting condensation of water vapor that brightens the surface an alternative explanation invokes transport and deposition of dust on the surface from the cap interior and later removal of that dust the decrease in cap albedo and accompanying increase in near surface atmospheric stability may be related to the annual minimum of polar storm activity near northern summer solstice

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

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

the role of the wind transported dust in slope streaks activity evidence from the hrsc data abstract slope streaks are gravity driven albedo features observed on martian slopes since the viking missions the debated mechanism of formation could involve alternatively dry granular flow or wet mass wasting a systematic mapping of slope streaks from the high resolution stereo camera is presented in this paper two regions known for their slope streaks activity have been studied the first one is located close to cerberus lava flow and the second one is inside the olympus mons aureole the statistics of slope streaks shapes measured from orthorectified images confirm previous results from mars orbiter camera surveys preferential orientations of slope streaks are reported slope streaks occur preferentially on west facing slopes at latitudes lower than 30 n for olympus and on south west facing slopes for cerberus wind directions derived from a general circulation model during the dusty season correlate with these orientations furthermore west facing slopes at olympus have a thicker dust cover these observations indicate that slope streaks are dust avalanches controlled by the preferential accumulation of dust in the downstream side of the wind flow the paucity of slope streaks at high latitudes and their preferential orientation on south facing slopes have been presented as an evidence for a potential role of h 2 o phase transition in triggering or flow the potential role of h 2 o cannot be ruled out from our observations but the dust avalanche model together with the atmospheric circulation could potentially explain all observations the role of h 2 o might be limited to a stabilizing effect of dust deposits on northward facing slopes at intermediate latitudes 30 n 33 n and on all slopes further north

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

radio occultation measurements of transient eddies in the northern hemisphere of mars 1 we have characterized the behavior of transient eddies in the northern hemisphere of mars through analysis of radio science rs occultation data from mars global surveyor mgs the weather in the lowest scale height above the surface at 55 n 80 n is dominated by shallow eastward moving baroclinic eddies distinguished by their intensity and coherence the vertical structure of these eddies is fully resolved by the rs measurements which also yield unique estimates of the near surface meridional winds implied by geostrophic balance we identified and characterized the most prominent eddies through space time analysis of rs measurements of geopotential height at 610 pa a few kilometers above the surface eddy activity appears as well defined modes with zonal wave numbers 1 3 and variations in the amplitudes of these modes tend to be anticorrelated so that a large amplitude in one mode is often accompanied by a small amplitude in the others the wave number and period of the dominant mode shift at intervals of 30 50 sols eddy winds near the surface vary distinctively with season in response to changes in eddy amplitude and zonal wave number the meridional winds peak sharply in two seasonal windows one in early to middle autumn and the other in middle to late winter separated by a lull around winter solstice comparisons with previous results reveal close connections with the transient eddies observed by the viking landers and with distinctive southward moving frontal dust storms observed by the mgs mars orbiter camera

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

the vertical dust profile over gale crater mars we create a vertically coarse but complete vertical profile of dust mixing ratio from the surface to the upper atmosphere over gale crater mars using the frequent joint atmospheric observations of the orbiting mars climate sounder mcs and the mars science laboratory msl curiosity rover using these data and an estimate of planetary boundary layer pbl depth from the marswrf general circulation model we divide the vertical column into three regions the first region is the gale crater pbl the second is the mcs sampled region and the third is between these first two we solve for a well mixed dust mixing ratio within this third middle layer of atmosphere to complete the profile we identify a unique seasonal cycle of dust within each atmospheric layer within the gale pbl dust mixing ratio maximizes near southern hemisphere summer solstice ls 270 and minimizes near winter solstice ls 90 100 with a smooth sinusoidal transition between them however the layer above gale crater and below the mcs sampled region more closely follows the global opacity cycle and has a maximum in opacity near ls 240 and exhibits a local minimum associated with the solsticial pause in dust storm activity near ls 270 with knowledge of the complete vertical dust profile we can also assess the frequency of high altitude dust layers over gale we determine that 36 of mcs profiles near gale crater contain an absolute high altitude dust layer wherein the dust mixing ratio is the maximum in the entire vertical column

modeling aeolian sediment transport thresholds on physically rough martian surfaces a shear stress partitioning approach article i nfo this paper explores the effect that large roughness elements 0 30 m 0 26 m 0 36 m may have on entrainment of sediment by martian winds using a shear stress partitioning approach based on a model developed by raupach et al raupach m r gillette d a leys j f 1993 the effect of roughness elements on wind erosion threshold journal of geophysical research 98 d2 3023 3029 this model predicts the shear stress partitioning ratio defined as the percent reduction in shear stress on the intervening surface between the roughness elements as compared to the surface in the absence of those elements this ratio is based on knowledge of the geometric properties of the roughness elements the characteristic drag coefficients of the elements and the surface and the assumed effect these elements have on the spatial distribution of the mean and maximum shear stresses on mars unlike on earth the shear stress partitioning caused by roughness can be non linear in that the drag coefficients for the surface as well as for the roughness itself show reynolds number dependencies for the reported range of martian wind speeds the shear stress partitioning model of raupach et al is used to evaluate how conditions of the martian atmosphere will affect the threshold shear stress ratio for martian surfaces over a range of values of roughness density using as an example a 125 m diameter particle with an estimated threshold shear stress on mars of 0 06 n m 2

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 origin evolution and trajectory of large dust storms on mars during mars years 24 30 1999 2011 abstract mars daily global maps mdgm derived from the mars global surveyor mgs mars orbiter camera moc and mars reconnaissance orbiter mro mars color imager marci are used to study the distribution and evolution of large dust storms over the period from mars years 24 30 1999 2001 large storms are defined here as discrete dust events visible in image sequences extending over at least 5 sols mars days and where the dust covers areas beyond the origination region a total of 65 large dust storms meeting these criteria are identified during the observational period and all are observed during the l s 135 30 seasonal window dust storms originating in the northern and southern hemispheres appear to form two distinct families all but two of the storms originating in the northern hemisphere are observed in two seasonal windows at l s 180 240 and l s 305 350 while all but two of those originating in the southern hemisphere are observed during l s 135 245 none of the large dust storms originating in the northern hemisphere are observed to develop to global scale but some of them develop into large regional storms with peak area 1 10 7 km 2 and duration on the order of several weeks in comparison large dust storms originating in the southern hemisphere are typically much smaller except notably in the two cases that expanded to global scale the 2001 and 2007 global storms distinct locations of preferred storm origination emerge from the dust storm image sequences including acidalia utopia arcadia and hellas a route trajectory graph for the observed sequences is provided the routes are highly asymmetric between the two hemispheres in the south for non global dust storms the main routes are primarily oriented eastwest whereas in the north the routes are primarily north south and zonally concentrated into meridional channels in a few impressive cases storms originating in the northern hemisphere are observed to flush through acidalia and utopia across the equator and then branch in the low and mid southern latitudes the origin of the 2007 global dust storm is ambiguous from the imaging data immediately prior to the global storm a dust storm sequence from chryse is identified this storm s connection to the explosive expansion observed to start from noachis west hellas is unclear due to image coverage this paper further identifies and describes three different styles of dust storm development which we refer to as consecutive dust storms sequential activation and merging the evolution of a given dust storm sequence can exhibit different combinations of these growth styles at different stages of development dust storm sequences can overlap in time which makes them good candidate to grow into larger scale

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

wind driven particle mobility on mars insights from mars exploration rover observations at el dorado and surroundings at gusev crater 1 the ripple field known as el dorado was a unique stop on spirit s traverse where dust raising active mafic sand ripples and larger inactive coarse grained ripples interact illuminating several long standing issues of martian dust mobility sand mobility and the origin of transverse aeolian ridges strong regional wind events endured by spirit caused perceptible migration of ripple crests in deposits sse of el dorado erasure of tracks in sandy areas and changes to dust mantling the site localized thermal vortices swept across el dorado leaving paths of reduced dust but without perceptibly damaging nearly cohesionless sandy ripple crests from orbit winds responsible for frequently raising clay sized dust into the atmosphere do not seem to significantly affect dunes composed of more easily entrained sand sized particles a long standing paradox this disparity between dust mobilization and sand mobilization on mars is due largely to two factors 1 dust occurs on the surface as fragile low density sand sized aggregates that are easily entrained and disrupted compared with clay sized air fall particles and 2 induration of regolith is pervasive light toned bed forms investigated at gusev are coarse grained ripples an interpretation we propose for many of the smallest linear light toned bed forms of uncertain origin seen in high resolution orbital images across mars on earth wind can organize bimodal or poorly sorted loose sediment into coarse grained ripples coarse grained ripples could be relatively common on mars because development of durable well sorted sediments analogous to terrestrial aeolian quartz sand deposits is restricted by the lack of free quartz and limited hydraulic sediment processing

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

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

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

an exsolution origin for low temperature sulfides at the hemlo gold deposit ontario canada many aspects of the timing and genesis of the archean hemlo gold deposit are unresolved pre syn and postmetamorphic models have been proposed the presence of abundant low temperature sulfide minerals within highly deformed sillimanite grade host rocks has been used to support a postmetamorphic origin for the deposit however the present sb as hg ore assemblage including cinnabar realgar orpiment assemblages developed through a sequence of exsolution events during postpeak metamorphic cooling at peak metamorphism most of the as and hg along with tl cu zn and minor fe was incorporated into a high temperature antimonian sulfosalt in the lower amphibolite facies or upper greenschist facies impure hg zn s exsolved from the high temperature phase an impure chalcopyrite and native antimony exsolved from the host sulfosalt soon after leaving behind an sb 2 s 3 as 2 s 3 solid solution further cooling resulted in the exsolution of cinnabar and mercurian sphalerite from the hg zn s impurities in the cinnabar and chalcopyrite exsolved to form aktashite arsenopyrite and native antimony eventually orpiment exsolved from the arsenic bearing stibnite late retrograde events converted the free orpiment to realgar and remobilized the realgar over short distances along with cinnabar and native antimony the history of sequential sulfide exsolution along with the deformed nature of the sb as hg bearing veins and their metamorphosed alteration selvages suggests that the metals were introduced prior to or during peak metamorphism

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

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

three decades of martian surface changes 1 the surface of mars has changed dramatically during the three decades spanned by spacecraft exploration comparisons of mars global surveyor images with viking and mariner 9 pictures suggest that more than one third of mars surface area has brightened or darkened by at least 10 such albedo changes could produce significant effects on solar heating and the global circulation of winds across the planet all of the major changes took place in areas of moderate to high thermal inertia and rock abundance consistent with burial of rocky surfaces by thin dust layers deposited during dust storms and subsequent exposure of the rocky surfaces by aeolian erosion several distinct mechanisms contribute to aeolian erosion on mars prevailing winds dominate erosion at low latitudes producing diffuse albedo boundaries and elongated wind streaks generally oriented in the direction of southern summer winds dust devils darken the mid to high latitudes from 45 to 70 degrees during the summer seasons forming irregular albedo patterns consisting of dark linear tracks dust storms produce regional albedo variations with distinct but irregular margins dark sand dunes in southern high latitudes appear to be associated with regional darkening that displays diffuse albedo boundaries no surface changes were observed to repeat regularly on an annual basis but many of the changes took place in areas that alternate episodically between high and low albedo states as thin mantles of dust are deposited and later stripped off hence the face of mars remains recognizable after a century of telescopic observations in spite of the enormous extent of alteration that has taken place during the era of spacecraft exploration

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

hemispheric difference in the momentum transport by waves encircling the summer polar region of mars observed by mgs tes 1 hemispheric difference in the momentum transport by atmospheric waves in the martian summer polar region was investigated by using the atmospheric temperature profiles taken by mgs tes in the southern polar region isolated zonal wave number 1 temperature disturbances were prominent and upward ep eliassen palm fluxes were found indicating the existence of planetary waves while they were obscure in the northern polar region this north south difference is attributed to the difference in co2 polar cap retreat the asymmetric retreat of the southern polar cap which remains throughout the summer creates near surface temperature anomalies with the zonal wave number of unity and resultant planetary waves while the nearly symmetric retreat of the northern polar cap do not create such disturbances the momentum transport in the southern polar region will drive a localized meridional circulation with ascent at 70 s 80 s and descent over the pole this meridional circulation would increase the atmospheric temperature by 10 k near the pole and transport dust that is lifted up by local dust storms

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