transport processes induced by metastable boiling water under martian surface conditions liquid water on the martian surface is expected to be metastable owing to low atmospheric pressure experiments at martian conditions reveal that water and briny flows induce grain saltation and slope destabilization with geomorphic consequences

formation of recurring slope lineae on mars by rarefied gas triggered granular flows active dark flows known as recurring slope lineae have been observed on the warmest slopes of equatorial mars the morphology composition and seasonality of the lineae suggest a role of liquid water in their formation however internal and atmospheric sources of water appear to be insufficient to sustain the observed slope activity experimental evidence suggests that under the low atmospheric pressure at the surface of mars gas can flow upwards through porous martian soil due to thermal creep under surface regions heated by the sun and disturb small particles here we present numerical simulations to demonstrate that such a dry process involving the pumping of rarefied gas in the martian soil due to temperature contrasts can explain the formation of the recurring slope lineae in our simulations solar irradiation followed by shadow significantly reduces the angle of repose due to the resulting temporary temperature gradients over shaded terrain and leads to flow at intermediate slope angles the simulated flow locations are consistent with observed recurring slope lineae that initiate in rough and bouldered terrains with local shadows over the soil we suggest that this dry avalanche process can explain the formation of the recurring slope lineae on mars without requiring liquid water or co2 frost activity transient streaks on martian slopes have been attributed to liquid water simulations show that a dry avalanche process involving the flow of gas in the martian soil due to temperature contrasts can instead explain these recurring features

the role of radiogenic heat production in the thermal evolution of a proterozoic granulite facies orogenic belt eastern ghats indian shield abstract the eastern ghats belt egb is a deeply eroded proterozoic orogenic belt juxtaposed against the archaean dharwar bastar singhbhum cratons in the indian shield the tectono metamorphic history of this belt is broadly similar to the grenvillian orogenic belts the egb exposes dominantly the granulite facies rocks such as charnockites khondalites and migmatitic gneisses with less abundant intermediate to mafic granulites the granulites are intruded by small plutons of granites syenites and anorthosites the northern and southern parts of the belt negb and segb have distinct crustal histories but 1600 1000 550 ma old tectono metamorphic events are common to both the belts in this research we attempt to understand the present day and past thermal state of this orogen on the basis of our radioelement k u and th measurements at 562 sites using in situ gamma ray spectrometry with other geological and geophysical constraints the dominant rock types of the negb and segb have similar radioelement abundances 3 k 3 ppm u and 30 ppm th and heat production heat production of charnockites gneisses khondalites and intermediate granulites of the negb is 2 9 2 8 2 9 and 1 1 w m 3 respectively in the segb they are 2 7 2 5 2 8 and 0 6 w m 3 respectively and the mafic granulites are the lowest in heat production 0 3 w m 3 on the basis of the heat production data and crustal petrologic models we show that the crustal contribution of the negb and segb is 54 and 45 mw m 2 respectively which are broadly in good agreement with the available surface heat flow data thermal models of the present day egb crust indicate that the temperature at the moho is 550 c radioelements and heat production of the eastern ghats granulites are higher than the other granulite belts in the indian shield the crustal radiogenic heat contribution and moho temperatures of the egb are higher than the adjoining archaean cratons this could also be responsible for the development of inverted metamorphic isograds in the tectonic boundary between the egb and the adjoining cratons during a collisional orogenic event at about 550 ma ago

the chimalpahad anorthosite complex and associated basaltic amphibolites nellore schist belt india magma chamber and roof of a proterozoic island arc abstract new major and trace element data on the proterozoic chimalpahad layered anorthositic complex and associated basaltic amphibolites of the nellore schist belt of south india provide new constraints on their petrogenesis and geodynamic setting the complex consists of layered anorthosites leucogabbros gabbros ultramafic rocks and is spatially associated with basaltic amphibolites despite deformation and metamorphism primary cumulate textures and igneous layering are locally well preserved throughout the complex whereas the amphibolites display diverse ree systematics the chimalpahad anorthositic gabbroic rocks are characterized by moderately depleted to strongly enriched lree patterns and by flat to depleted hree patterns the field relations major and trace element compositions of the basaltic amphibolites suggest that they are petrogenetically related to the anorthositic gabbroic rocks by fractional crystallization the anorthositic rocks and the basaltic amphibolites share the depletion of nb relative to th and la on primitive mantle normalized diagrams they exhibit signatures of arc magmatic rocks such as high lile and lree relative to the hfse and hree as well as high ba nb ba zr sr y la yb ratios that mimic chondrite normalized ree and primitive mantle normalized trace element patterns of arc magmas similarly on log transformed tectonic discrimination diagrams the chimalpahad rocks plot within the field of phanerozoic magmatic arcs consistent with a subduction zone origin on the basis of field relations and geochemical characteristics the chimalpahad complex is interpreted as a fragment of a magma chamber of an island arc which is tectonically juxtaposed against its original volcanic cover a new preliminary sm nd date of anorthosite from the chimalpahad complex indicates a model age of 1170 ma

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

magnetotelluric analysis using mohr circles the mohr circle most commonly met in the analysis of mechanical stress is used to depict magnetotelluric impedance information taking the real and quadrature parts of magnetotelluric tensors separately the magnetotelluric concepts of two dimensionality three dimensionality skew and anisotropy are then all given quantitative expression on a diagram as are various magnetotelluric invariants in particular a new invariant the central impedance becomes evident in a discussion of effective impedances some insight is gained into impedance rotations and an anisotropy angle is defined analogous to skew angle mohr circles are also tested to depict the effects of the shear and twist operations on a regionally two dimensional structure generally the application of shear or twist results in an impedance tensor with a mohr circle of typical three dimensional form

electromagnetic induction in an inhomogeneous conductive thin sheet distinguishing between the electromagnetic em response of a subsurface conductor and the em response of an overburden whose conductivity and or thickness varies laterally requires a capability to calculate the em response of both types of conductor while methods for calculating the response of some simple subsurface conductors such as dipping rectangular sheets are already available methods for computing the response of an irregular overburden are not common using price s analysis we have formulated two numerical techniques for calculating the response of a laterally varying overburden which is thin and flat and which lies on a perfectly resistive subspace the first technique is a frequency domain method in which a large matrix equation is solved to find the horizontal wavenumber components of the secondary vertical magnetic field the method is best suited to calculating the response of the overburden when the em source and receiver are located above the sheet such as in airborne em systems helicopter em profiles calculated using this technique have been checked against a simple scale model the second method calculates the time domain step response of the overburden by time stepping the vertical component of the magnetic field the method is suitable for calculating the response of the overburden when the em source is a large transmitter loop close to the overburden using the time domain method to investigate the response of simple conductance structures illustrates that the zero crossing of the vertical magnetic field moves more slowly across conductive regions than across resistive regions this is because the rate of decay of the vertical field in a region varies in proportion to the resistance of the region a response profile from a utem survey shows a response that could be interpreted as due to a dipping subsurface conductor this response has been modeled using the time domain method and a geologically acceptable pattern of lateral variations in the overburden conductance yields a response close to the measured em response thus a subsurface conductor need not lie below the profile line to explain the response

slope elevation and thermal inertia trends of martian recurring slope lineae initiation and termination points multiple possible processes occurring on coarse sandy slopes abstract recurring slope lineae rsl are dark linear features on the surface of mars that advance incrementally downslope fading and re growing annually numerous hypotheses have been proposed to explain rsl formation including wet models that involve liquid water or brines and dry mechanisms involving liquid free mass wasting or solid vapor phase changes that trigger granular flow in part hypotheses to explain rsl formation rely on observations of the physical characteristics of the slopes on which rsl are present to determine if rsl exhibit physical characteristics typical of one particular formation mechanism we examined the initiation and termination points of over 10 000 rsl across 16 confirmed rsl sites to determine their slope elevation orientation and thermal inertia rsl typically form within an envelope of high elevations at each mapping site are oriented equatorward and west and have hillslope thermal inertia values consistent with sand and gravel notably the rsl begin and end at slopes above within and below the angle of repose required to trigger and sustain dry granular flows sensitivity testing indicates that these slope values are not a result of pixel scale noise discontinuous rsl are observed at several study sites the slope and thermal inertia values of the rsl as well as these additional geomorphic observations of discontinuous dark features are not consistent with the characteristics of dry flows in which continuous dust avalanches begin within the dynamic angle of repose and terminate within the static angle of repose although rsl are found to be common on coarse sandy and rocky slopes not all sandy slopes in rsl regions that are close to the angle of repose contain rsl we conclude that mechanisms other than dry mass wasting are needed to explain all of the observed geomorphic characteristics of rsl source and termination points

hirise observations of recurring slope lineae rsl during southern summer on mars abstract recurring slope lineae rsl are active features on mars that might require flowing water most examples observed through 2011 formed on steep equator facing slopes in the southern mid latitudes they form and grow during warm seasons and fade and often completely disappear during colder seasons but recur over multiple mars years they are recognizable by their incremental growth relatively low albedo and downhill orientation we examined all images acquired by hirise during l s 250 10 slightly longer than southern summer l s 270 360 of mars years 30 31 03 2011 10 2011 and supplemented our results with data from previous studies to better understand the geologic context and characteristics of rsl we also confirmed candidate and likely sites from previous studies and discovered new rsl sites we report 13 confirmed rsl sites including the 7 in mcewen et al mcewen et al 2011 science 333 6043 740 743 the observed seasonality latitudinal and slope orientation preferences and themis brightness temperatures indicate that rsl require warm temperatures to form we conclude that rsl are a unique phenomenon on mars clearly distinct from other slope processes that occur at high latitudes associated with seasonal co 2 frost and episodic mass wasting on equatorial slopes however only 41 82 out of 200 of the sites that present apparently suitable conditions for rsl formation steep equator facing rocky slopes with bedrock exposure in the southern mid latitudes 28 60 s contain any candidate rsl with confirmed rsl present only in 7 13 sites of those locations significant variability in abundance size and exact location of rsl is also observed at most sites indicating additional controls such as availability of water or salts that might be playing a crucial role

neoproterozoic deformation at a boundary zone between the nellore khammam schist belt and pakhal basin se india strain analysis of deformed pebbles abstract in the kinnerasani area in southeastern india the terrain boundary between the archean nellore khammam schist belt and the proterozoic pakhal supergroup overlying the dharwar bastar cratons can be observed we analyzed the mesoscopic and microscopic structural features of the highly deformed pebbles in the basal conglomerate bed of the pakhal supergroup that occurs at the terrain boundary the results of the analysis of the pebbles suggest that 1 deformation of pebbles resulted from ductile deformation during peak metamorphism 2 the mode of strain is plane strain to constrictive and maximum elongation located to be vertical and 3 the apparent stretch of the pebbles is up to 300 in the nellore khammam schist belt quartz grains constituting the quartz layer of the feldspathized gneiss folded by the last phase deformation also show vertical maximum stretching in constrictive strain this observation suggests that the deformational features at least the mode of strain during the last phase deformation is comparable to the deformation forming elongated pebbles of the pakhal conglomerate the last phase deformation structures of the nellore khammam schist belt are well observed near the terrain boundary this indicates that the pakhal deformation overprinted the rocks of the nellore khammam schist belt near the boundary and that their tectonic juxtaposition occurred during or before this deformation period because the pakhal deformation took place during or soon after the peak metamorphism of the pakhal supergroup which is known to be 1000 ma and the last metamorphism of the nellore khammam schist belt in the khammam area were reported to be 1100 ma the tectonic juxtaposition between the pakhal supergroup and nellore khammam schist belt was around 1000 1100 ma

martian gullies in the southern mid latitudes of mars evidence for climate controlled formation of young fluvial features based upon local and global topography a new survey of mars orbiter camera moc narrow angle images of gullies in the 30 45 s latitude band includes their distribution morphology local topographic setting orientation elevation and slopes these new data show that gully formation is favored over a specific range of conditions elevation 5000 to 3000 m slope 10 and orientation 83 8 on pole facing slopes these data and the frequent occurrence of gullies on isolated topographic highs lead us to support the conclusion that climatic related processes of volatile accumulation and melting driven by orbital variations are the most likely candidate for processes responsible for the geologically recent formation of martian gullies

age and tectonic evolution of neoproterozoic ductile shear zones in the southern granulite terrain of india with implications for gondwana studies 1 the high grade rocks of the southern granulite terrain sgt of peninsular india are bounded to the north by the archean dharwar craton another high grade terrane the mesoproterozoic eastern ghats occurs to the northeast of the sgt the tectonic relationship between these crustal domains is complex we present new geochronological and structural data that indicate a continuation of the dharwar craton into the southern granulite terrain as far south as a newly identified neoproterozoic shear zone here named the karur kamban painavu trichur shear zone kkptsz south of the kkptsz mesoproterozoic dates of the sgt are similar to those recorded in the eastern ghats and the two domains may have been conterminous thirty three new u pb th single zircon and monazite dates of samples from six structural transects across the regional shear zones indicate that the sgt has experienced at least seven thermo tectonic events at 2 5 ga 2 0 ga 1 6 ga 1 0 ga 800 ma 600 ma and 550 ma and two distinct episodes of metasomatism charnockitization between 2 50 2 53 and between 0 55 0 53 ga deformation along a number of major shear zones in the sgt is neoproterozoic to earliest paleozoic in age with an early phase d2 concentrated between 700 800 ma and a later phase d3 between 550 and 600 ma major charnockitization 530 550 ma post dates d3 and is in turn overprinted by granitization retrogression and uplift between 525 and 480 ma the kkptsz active between 560 and 570 ma is either a terrane boundary or a tectonized decollement between cover and archean basement rocks represented by predominantly paragneisses to the south and orthogneisses to the north respectively other regional neoproterozoic shear zones do not appear to separate allochthonous terranes as previously suggested on the basis of nd model ages and rb sr biotite whole rock dates the neoproterozoic cambrian tectonothermal history of the sgt and eastern ghats is similar to that recorded in parts of madagascar east africa and antarctica and is used to reconstruct parts of central gondwana here named the deccan continent with more robust confidence

u pb zircon geochronology of the paleogene neogene volcanism in the nw anatolia its implications for the late mesozoic cenozoic geodynamic evolution of the aegean abstract the northern aegean region was shaped by subduction obduction collision and post collisional extension processes two areas in this region the rhodope thrace biga peninsula to the west and armutlu almacik nallihan the central sakarya to the east are characterized by extensive eocene to miocene post collisional magmatic associations we suggest that comparison of the cenozoic magmatic events of these two regions may provide insights into the late mesozoic to cenozoic tectonic evolution of the aegean with this aim we present an improved cenozoic stratigraphy of the biga peninsula derived from a new comprehensive set of u pb zircon age data obtained from the eocene to miocene volcanic units in the region the compiled radiometric age data show that calc alkaline volcanic activity occurred at 43 15 ma in the biga peninsula 43 17 ma in the rhodope and thrace regions and 53 38 ma in the armutlu almacik nallihan region which are slightly overlapping we discuss the possible cause for the distinct cenozoic geodynamic evolution of the eastern and western parts of the region and propose that the rhodope thrace and biga regions in the north aegean share the same late mesozoic to cenozoic geodynamic evolution which is consistent with continuous subduction crustal accretion southwestward trench migration and accompanying extension all preceded by the late cretaceous paleocene collision along the vardar suture zone in contrast the armutlu almacik nallihan region was shaped by slab break off and related processes following the late cretaceous paleocene collision along the izmir ankara suture zone the eastern and western parts of the region are presently separated by a northeast southwest trending transfer zone that was likely originally present as a transform fault in the subducted tethys oceanic crust and demonstrates that the regional geodynamic evolution can be strongly influenced by the geographical distribution of geologic features on the subducting plate

alkaline magmatism versus collision tectonics in the eastern ghats belt india constraints from structural studies in the koraput complex abstract linear domains of deformed alkaline rocks and carbonatites have recently been identified as representing sites of ancient suture zones in peninsular india the western margin of the proterozoic eastern ghats belt egb is characterized by a series of alkaline plutons that are aligned close to the contact with the archaean craton most of the complexes were deformed and metamorphosed during a subsequent orogenic event unlike other plutons in the belt the alkaline complex at koraput reportedly escaped deformation and granulite facies metamorphism forming an anomalous entity within the zone multiply deformed country rocks hosting this complex underwent syn d1cr granulite facies metamorphism followed by d2cr thrusting with pervasive shearing along a ne sw trending foliation a second granulite facies event followed localized d3cr shearing within the koraput complex strain partitioning was responsible for preserving igneous textures in the gabbroic core but aligned magmatic amphibole needles and plagioclase laths occasionally define a s1ac fabric along the margins s1ac is rotated parallel to a ne trending east dipping s2ac fabric in the gabbro fringing syenodiorite and nepheline syenite bands locally d3ac shearing follows d2ac deformation s2ac and s3ac parallel s2cr and s3cr in the country rocks high grade metamorphism represented by recrystallization of amphibole and plagioclase and breakdown of amphibole and biotite to garnet pyroxene and k feldspar in the complex follows d3ac unlike earlier reports therefore the koraput body is also deformed and metamorphosed the aligned alkaline complexes in the egb probably represent deformed alkaline rocks and carbonatites formed by rifting related to an earlier episode of continental break up that were deformed during subsequent juxtaposition of the egb with the archaean craton this supports the contention that the western margin of the egb and its contact with the archaean craton is a suture zone related to the indo antarctica collision event

mapping of tectonic corridors through hidden parts of the greater dharwar terrane southern india abstract the dharwar craton india has been divided into western and eastern domains by a tectonic boundary between the closepet granite and chitradurga schist belt it has been noted that only the central portion of the dharwar craton is exposed its northern projection is buried beneath the deccan traps and its southern margin merges with a high grade metamorphic transition of late archean age resolution of structure and extent of the greater dharwar terrane gdt beneath its northern and southern end the deccan traps metamorphic transition zone and cuddapah basin thus remains unsolved results of deep geophysical probings have been examined along with associated geological and tectonic data the analysis leads to a delineation of palaeo accretionary corridors extending under the deccan trap cover along which two damaging stable continental region earthquakes koyna and latur occurred veeraswamy and raval 2005 b it is seen that the latur earthquake seem to lies within an unsuspected tectonic corridor which bifurcates the eastern dharwar craton edc into eastern dharwar craton 1 and eastern dharwar craton 2 passing through the cuddapah basin c possibility of the palghat cauvery shear zone connecting to the 2 5 ga metamorphic karimnagar granulite belt through the interface between napier nc and rayner rc complexes of east antarctica and d the indication that the bavali moyar bhavani mettur and palghat cauvery shear zones form the southern margins of the western dharwar craton eastern dharwar craton 1 and eastern dharwar craton 2 respectively

dismembered ophiolites in paleoproterozoic nappe complexes of kandra and gurramkonda south india abstract the constitution and structural architecture of ophiolites is important in the understanding of cratonic growth through subduction collision accretion history in the precambrian terrains the nellore schist belt nsb sandwiched between the eastern ghats belt egb and the eastern dharwar craton south india is known to have deformed remnants of ocean plate stratigraphy ops as at kanigiri and kandra suggesting multiple cycle of ocean opening and closure in the paleoproterozoic mesoproterozic interval the outcrop details and structural architecture of the paleoproterozoic kandra complex with geochemical character of subduction related ophiolites is described and analyzed to better constrain the accretion collision history along the southeastern margin of the indian craton imbricate thrust slices between kandra and arimanupadu host slivers of hornblende metagabbro thick massive to pillowed metabasalt sheets sheeted meta dolerite dykes and thin metapsammite and metapelite interstratified with metabasalt comparable to layer 2a of oceanic crust contractional deformation in interlayered metabasalt and quartzite around kandra is accommodated by south dipping imbricate thrust systems and n ne vergent folds the wnw trending thrust system with dominant tectonic transport toward northeast is oblique to overall n s trend of the nsb or the egb further east intercalated metabasalts deep water turbidites and thin metacherts around gurramkonda are deformed into sw vergent imbricate thrust system here occurrence of metabasalt sheets along individual thrusts suggest syntectonic emplacement of some basalts as the subducted and scraped upper oceanic crust was incorporated in the acrcetionary prism the rock sequences around kandra and gurramkonda comprising incomplete ops are tectonically stacked over granites of the eastern dharwar craton margin bivergent thrust systems around kandra possibly root into a detachment separating layers 1 2 from more rigid deeper layers cf layer 3 of oceanic crust as indicated by absence of significant volume of ultramafic rocks at the current outcrop level

distortion of magnetotelluric sounding curves by three dimensional structures distortions of magnetotelluric fields caused by three dimensional 3 d structures can be severe and are not predictable using one dimensional or two dimensional modeling i used a 3 d modeling algorithm based upon an extension of a generalized thin sheet analysis due to ranganayaki and madden 1980 to examine field distortions in crustal environments three major physical mechanisms cause these distortions these mechanisms are resistive coupling between the electrical mantle and upper crust resistive coupling between conductive features within the upper crust and local induction of current loops within good conductors each mechanism produces different spatial and frequency effects upon the background field so identification of the dominant mechanism can be used as an interpretational aid i finally use this analysis to identify distortion mechanisms seen in magnetotelluric data from beowawe nevada to aid in an interpretation of that area

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

laboratory studies of perchlorate phase transitions support for metastable aqueous perchlorate solutions on mars abstract perchlorate salts recently discovered on mars are known to readily absorb water vapor from the atmosphere and deliquesce into the aqueous phase at room temperature here we study the deliquescence crystalline solid to liquid transition and efflorescence liquid to crystalline solid transition of perchlorate salts at low temperatures relevant to mars a raman microscope and environmental cell were used to determine the deliquescence relative humidity drh and efflorescence relative humidity erh of naclo 4 and mg clo 4 2 as a function of temperature and hydration state we find that the deliquescence of anhydrous naclo 4 is only slightly dependent on temperature and occurs at 38 rh the drh of naclo 4 h 2 o increases with decreasing temperature from 51 at 273 k to 64 at 228 k the drh of mg clo 4 2 6h 2 o also increases with decreasing temperature from 42 at 273 k to 64 at 223 k the efflorescence of both naclo 4 and mg clo 4 2 salt solutions occurs at a lower rh than deliquescence due to the kinetic inhibition of crystallization for all temperatures studied the erh values of naclo 4 and mg clo 4 2 are 13 and 19 respectively these results indicate perchlorate salts can exist as metastable supersaturated solutions over a wide range of rh and temperature conditions summer diurnal temperature and relative humidity cycles at low latitudes on mars could allow the surface salts to be aqueous for several hours per day

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

recognition of electromagnetic overburden anomalies with horizontal loop electromagnetic survey data an analog modeling program was conducted to investigate the electromagnetic em response of nonuniform conductive overburden layers with the horizontal loop technique of geophysical prospecting several characteristics of the response that will help to differentiate between the em response of nonuniform overburden layers and the response of bedrock mineralized conductors are reported to recognize these characteristics survey data at several frequencies and coil separations are required it was observed that the response of a ramp like a ridge like and a valley like inhomogeneity in the overburden can be mistaken as caused by bedrock conductors in the case of the ramp and ridge inhomogeneities the migration of the negative peak anomaly observed in profiles surveyed at different coil separations was one of its more diagnostic characteristics prominent positive shoulders as well as an abnormal distance between crossovers of a given detected field anomaly might be the first indication of the presence

the timescale and mechanism of granulite formation at kurunegala sri lanka incipient charnockite formation at kurunegala in sri lanka is characterized by the growth of orthopyroxene at the expense of amphibole and biotite in an originally homogeneous gneiss mineral equilibria in the charnockite assemblage record pressure temperature p t conditions of 738 60 c and 6 9 1 2 kbar at 17 0 1 2 log fo2 and ah2o 0 18 0 16 wholerock trace element and isotopic measurements show that charnockite formation was accompanied by a systematic depletion of sm rb pb u sr nd with a fractionation of rb sr sm nd and th u ratios and crystallization of the charnockite assemblage at 535 5 ma major element fe mg ca and sm nd equilibration between minerals occurred at 524 9 ma whereas pb and rb sr underwent continued exchange to 501 5 ma and 486 1 ma respectively trace element data for both amphibolite and charnockite minerals show that depletion on a whole rock scale can be accounted for either by changes in mineral modes or trace element abundances within the immediate area of dehydration the fractionation of sm nd on a whole rock scale is controlled by the breakdown of amphibole without the growth of a major new host phase for sm in the charnockite rubidium and sr are dependent on the relative behaviour of biotite plagioclase and alkali feldspar modelling of dehydration melting involving the breakdown of amphibole biotite and alkali feldspar reproduces the observed sm nd and rb sr fractionation and indicates the loss of small melt fractions on a cm scale from the charnockite these observations suggest that partial melting is the most plausible means of effecting both the dehydration and depletion that accompanies charnockite formation

shallow marine to pelagic sediments from a dismembered ophiolite kandra southern india glimpses of ancient subduction zone related sedimentation abstract a suprasubduction zone oceanic back arc setting for the paleoproterozoic kandra ophiolite complex koc in southern india has been suggested from geochemical signatures the telescoped segments of thin deformed sedimentary successions of shallow marine to pelagic affinity overlying a basaltic substrate and preserved within thrust slices of the koc are tectonically juxtaposed against the eastern dharwar craton margin in the northern thrust slice kandra village succession about 150 m of sedimentary strata show intercalation of quartz arenite and basaltic flow in the lower part grading upwards to heterolithic sandstone mudstone deposited above the storm wave base in the southeastern part of the koc gurramkonda succession deep water greywacke turbidite pelagic chert mafic tuff and volcaniclastics and quartz arenite deposited below the storm wave base are preserved as thrust bound packets intermittent basaltic outpourings punctuated deeper water deposition as evidenced by alternate metachert and metabasalt layers and emplacement of basaltic rocks along small thrusts which transpose stratification craton margin sediments consists of immature coarse terrigenous clastics intercalated with thin mafic tuff suggesting influence of mass flow processes giving way to fluvial sedimentation in the lower part of the udaigiri group further up fine grained plane laminated siltstone shale with rippled sandstone lenses grade upward to compositionally mature quartz arenite deposited close to the craton margin with signatures of tidal and wave reworking the association of stratigraphic successions of two contrasting depositional environments in the koc adds to the spectrum of variation of sedimentary collage of the ocean plate stratigraphy the kandra village and gurramkonda successions of the koc possibly represent ancient arc trench milieu and shallower part of oceanic marginal basin respectively paleoproterozoic subduction accretion process led to collapse of these basins and tectonic emplacement of the koc against the eastern dharwar craton margin which hosted near shore sedimentary succession of the udaigiri group occurring west of the koc

morphometry of small recent impact craters on mars size and terrain dependence short term modification most recent studies of crater morphometry on mars have addressed large craters d 5 km using elevation models derived from laser altimetry in the present work we examine a global population of small 25 m d 5 km relatively well preserved simple impact craters using hirise stereo derived elevation models we find that scaling laws from prior studies of large simple craters generally overestimate the depth and volume at small diameters we show that crater rim curvature exhibits a strong diameter dependence that is well described by scaling laws for d 1 km above this diameter upper rim slopes begin to exceed typical repose angles and crater rims sharpen significantly this transition is likely the result of gravity driven collapse of the upper cavity walls during crater formation or short term modification in addition we identify a tendency for small craters d 500m to be more conical than large craters and we show that the average cavity cross section is well described by a power law with exponent 1 75 neither conical nor paraboloidal we also conduct a statistical comparison of crater subpopulations to illuminate trends with increasing modification and target strength these results have important implications for describing the initial condition of simple crater shape as a function of diameter and geological setting and for understanding how impact craters are modified on the martian surface over time

robust conductance estimates from spatial and temporal derivatives of borehole electromagnetic data abstractthe conductance of an infinite uniformly conductive thin sheet can be calculated using the ratio of the temporal gradient and the spatial gradient in the normal direction of any component or combination of components of the secondary magnetic field with standard borehole electromagnetic bhem systems the temporal gradient can either be measured or readily calculated from transient magnetic field data and the spatial gradient in the normal direction can be estimated using adjacent stations synthetic modeling demonstrates that for a finite thin sheet the magnitude of the field provides a robust and reliable apparent conductance in typical three component bhem survey configurations the accuracy in which the apparent conductance can be calculated is hindered by low spatial gradient signal values and can only be reliably estimated where the fields are large i e in close proximity to the target in a field example of bhem data collected over a massive sulfide deposit in sudbury ontario c

line current filtering of fixed loop transient electromagnetic data1 the vlf filtering technique of karous and hjelt has been applied to fixed loop step response transient electromagnetic data this allows the data measured in each channel to be converted to an equivalent current density pseudosection for a conductive half space the maximum value of the equivalent current density starts near the transmitter loop and migrates outwards as a function of delay time the rate of migration tends to increase as a function of delay time with the increase being faster for a surficial conductive layer than it is for a half space theoretical and field examples show that the currents tend to be more persistent in the relatively conductive areas so that a pseudosection which is the average of the current densities at all delay times will highlight the more conductive zones in resistive ground it is not so critical to average the pseudosections as a particular delay time may give a better idea of the conductivity structure for example the latest possible delay time will reveal the most conductive features

evaluation of wet and dry recurring slope lineae rsl formation mechanisms based on quantitative mapping of rsl in garni crater valles marineris mars abstract recurring slope lineae rsl are narrow 0 5 5 m low albedo features that incrementally lengthen down steep slopes during warm seasons fade in colder seasons and recur each mars year to reduce the effort involved in manually mapping and analyzing each rsl in garni crater we developed mapping and automated analysis of rsl maarsl to analyze a set of orthorectified high resolution imaging science experiment hirise images and a digital elevation map maarsl along with manual mapping allowed us to detect rsl compute descriptive statistics and characterize changes over time we mapped 2910 rsl in 22 orthoimages from mars year my 31 solar longitude ls 133 0 to my32 ls 323 7 the maarsl results confirmed that rsl lengthening and fading occur concurrently on slopes with the same orientation and many times within some individual rsl slope angles of rsl and a slope slump show that some rsl start stop and have mean slope angles that are below the angle of repose our analysis shows that rsl are actively lengthening on at least one slope facing direction in all hirise observations of the crater we also found that ne n and nw facing rsl in garni crater lengthened during times of increasing shortwave insolation while s and sw facing rsl lengthened during increasing and decreasing shortwave insolation a non orthorectified hirise image acquired shortly after the my34 dust storm and shows rsl on every slope facing direction which is anomalous with respect to observations prior to the dust storm we find that dust removal and deposition could explain the darkening and fading respectively of rsl and could also explain the apparent lack of material being transported observations of rsl lengthening and fading occur concurrently on slopes could suggest overprinting of dry granular flows dry flows could also explain the significant lengthening activity of every slope facing direction after a fresh layer of dust was deposited via the my34 dust storm alternatively briny shallow subsurface flows are consistent with observations of rsl on slopes below the angle of repose and those that exhibit concurrent lengthening and fading however the most significant problem with briny rsl flows is accessing a source of briny water and removing excess salt from the regolith

deformation pattern in the kurnool and nallarnalai groups in the northeastern part palnad area of the cuddapah basin south india and its implication on rodinia gondwana tectonics abstract the proterozoic basins of india adjoining the eastern ghats granulite belt eggb in eastern and southern india contain both mesproterozoic and neoproterozoic successions the intracratonic set up and contractional deformation fo the neoproterozoc successions in the paland sub basin in the northeastern part of cuddapah basin and similar crustal shortening in contemporaneous successions lying west of the eggb and nellore schist belt nsb are considered in relation to the proposed geodynamic evolution of the the rodinia and gondwana supercontinents tectonic shortening in the palnad sub basin northeast cuddapah partitioned into top to westnorthwest thrust shear flexural folds and cleavage development under overall e w contraction suggests foreland style continental shortening within an intracratonic set up a thrust sheet containing the nallamalai rocks and overlying the kurnool rocks in the northeastern part of palnad sub basin exhibits early tight to isoclinal folds and slaty phylllitic cleavage which can be correlated with early mesoproterozoic deformation structures in the nothern nallamalai fold belt nfb nne ssw trending folds and cleavage affect the kurnool group and overprint earlier structures in the thrust sheet thrusting of the nallamalai rocks and the later structures may have been related to convergence of the eastern ghats terrane and the east dharwar bastar craton during early neoproterozoic greenvillian and or later rejuvenation related to pan african amalgamation of east and west gondwana

petrological and geochemical characterization of proterozoic ophiolitic melange nellore khammam schist belt se india abstract the ophiolitic melange occurs close to a major fault within the metavolcanics of kanigiri area in the western margin of the khammam nellore schist belt andhra pradesh india the unique feature of kanigiri melange is the occurrence of ophiolitic bodies of various sizes most of which display petrological and geochemical characteristics typical of supra subduction zone oceanic crust the ophiolitic melange is composed mainly of blocks of variably deformed and metamorphosed pillow basalts serpentinized ultramafic rocks meta gabbros cherts and pelagic sediments in a pervasive scaly argillite matrix the melange has a tectonic contact with a granite intrusion and numerous thrust faults cut across the melange exposures primary magmatic features such as drainage cavities in pillow basalts magmatic layering in gabbros and clinopyroxene cumulates in ultramafic rocks are well preserved in low strain domains mafic components enclosed in the melange are characterized by low pressure secondary mineral assemblages retrograded from amphibolite down to greenschist facies as commonly observed in subducted and exhumed orogens all amphiboles in the studied fragments are calcic and cluster in the range from winchite actinolite to hornblende amphibole compositions are characterized by al 2 o 3 2 4 13 8 feo 5 13 k 2 o 0 04 0 7 and x mg 0 67 0 77 the metabasalt and wherlite samples exhibit light rare earth element lree enriched patterns and negative high field strength element hfse zr and ti consistent with a suprasubduction zone geodynamic setting a notable feature of both metabasalt and wherlite samples is their pronounced negative ce anomaly and a positive eu anomaly as observed in a number of modern island arc suites as the petrological features and the geochemical characteristics of the remnant fragments we analyzed in this study are reminiscent of their phanerozoic ophiolite counterparts we suggest that these rocks were derived from a proterozoic oceanic plate belonging to a suprasubduction ophiolite assemblage subduction zone geochemical signatures and ophiolite like crustal lithologies in the study region are consistent with the accretion of juvenile oceanic fragments to the pre existing continental blocks through a forearc continent collision

the water content of recurring slope lineae on mars observations of recurring slope lineae rsl from the high resolution imaging science experiment have been interpreted as present day seasonally variable liquid water flows however orbital spectroscopy has not confirmed the presence of liquid h2o only hydrated salts thermal emission imaging system themis temperature data and a numerical heat transfer model definitively constrain the amount of water associated with rsl surface temperature differences between rsl bearing and dry rsl free terrains are consistent with no water associated with rsl and based on measurement uncertainties limit the water content of rsl to at most 0 5 3 wt in addition distinct high thermal inertia regolith signatures expected with crust forming evaporitic salt deposits from cyclical briny water flows are not observed indicating low water salinity if any and or low enough volumes to prevent their formation alternatively observed salts may be preexisting in soils at low abundances i e near or below detection limits and largely immobile these rsl rich surfaces experience 100 k diurnal temperature oscillations possible freeze thaw cycles and or complete evaporation on time scales that challenge their habitability potential the unique surface temperature measurements provided by themis are consistent with a dry rsl hypothesis or at least significantly limit the water content of martian rsl

proterozoic events in the eastern ghats granulite belt india evidence from rb sr sm nd systematics and shrimp dating metamorphic and protolith ages of five rock types mafic granulite orthopyroxene granulite leptynite sillimanite granite and metapelite from rayagada in the north central part of the eastern ghats granulite belt eggb india were determined from rb sr and sm nd whole rock and mineral isochrons in combination with shrimp u pb zircon data most of the whole rock isochron ages in both sm nd and rb sr systems point to either 1450 or 1000 ma and the mineral isochron ages are 1000 800 and 550 ma shrimp u pb zircon ages of 940 ma were obtained from metapelite which are in close agreement with the sm nd and rb sr isochron ages from all these data four age clusters 1450 1000 800 and 550 ma have been noted the 1450 ma ages are interpreted to represent igneous protolith formation of mafic granulite and leptynite the 1000 ma age cluster is regarded as the intrusion ages of sillimanite granite and charnockite and associated granulite facies metamorphism two other age clusters 800 a

mapping lateral changes in conductance of a thin sheet using time domain inductive electromagnetic data abstractwith the inductive electromagnetic geophysical method the laterally varying conductance of thin sheet models can be estimated either through a direct transform of the measured data or through inversion the direct transform called the simplified solution does not require grid or line data and is simple enough to be performed in the field because the conductance at a location is calculated directly from the ratio of two measured magnetic fields the vertical spatial and temporal derivative of the vertical magnetic field at that location however the simplified solution assumes that the secondary horizontal magnetic fields are zero and or that the sheet has a uniform conductance our nonapproximate solution called the full inversion does not make these assumptions but requires gridded data measurements of the secondary horizontal magnetic fields and more complicated inversion algorithms through forward modeling we found that the full inversion provides better results than the simplified

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

a deep groundwater origin for recurring slope lineae on mars the recurring slope lineae on mars have been hypothesized to originate from snow melting deliquescence dry flow or shallow groundwater except for the dry flow origin these hypotheses imply the presence of surficial or near surface volatiles placing the exploration and characterization of potential habitable environments within the reach of existing technology here we present observations from the high resolution imaging science experiment heat flow modelling and terrestrial analogues which indicate that the source of recurring slope lineae could be natural discharge along geological structures from briny aquifers within the cryosphere at depths of approximately 750 m spatial correlation between recurring slope lineae source regions and multi scale fractures such as joints and faults in the southern mid latitudes and in valles marineris suggests that recurring slope lineae preferably emanate from tectonic and impact related fractures we suggest that deep groundwater occasionally surfaces on mars in present day conditions observations and heat flow modelling suggest that briny groundwater surfacing from fractures forms recurring slope lineae on mars

an aeolian grainflow model for martian recurring slope lineae abstract recurring slope lineae rsl on mars have been enigmatic since their discovery their behavior resembles a seeping liquid but sources of water remain puzzling this work demonstrates that the properties of rsl are consistent with observed behaviors of martian and terrestrial aeolian processes specifically rsl are well explained as flows of sand that remove a thin coating of dust observed rsl properties are supportive of or consistent with this model which requires no liquid water or other exotic processes but rather indicates seasonal aeolian behavior these settings and behaviors resemble features observed by rovers and also explain the occurrence of many slope lineae on mars that do not meet the strict definition of rsl this indicates that rsl can be explained simply as aeolian features other processes may add complexities just as they could modify the behavior of any sand dune

probabilistic inversion of airborne electromagnetic data for basement conductors abstractprobabilistic inversion of airborne electromagnetic data is often approximated by a layered earth using a computationally efficient 1d kernel if the underlying framework accounts for prior beliefs on spatial correlation the inversion will be able to recover spatially coherent interfaces and associated uncertainties greenfield exploration using airborne electromagnetic data however often seeks to identify discrete economical targets in mature exploration provinces such bodies are frequently obscured by thick conductive regolith and the response of such economic basement conductors presents a challenge to any layered earth inversion a well known computationally efficient way to approximate the response of a basement conductor is to use a thin plate here we have extended a bayesian parametric bootstrap approach so that the basement of a spatially varying layered earth can contain a thin plate the resulting bayesian framework allowed for the inversion of basement conductors and associated

new observations of martian southern mid latitude recurring slope lineae rsl imply formation by freshwater subsurface flows abstract southern mid latitude sml recurring slope lineae rsl are narrow 0 5 5 m dark albedo features that emanate from bedrock and incrementally lengthen down steep slopes that preferentially face the equator we observe that sml rsl begin lengthening prior to southern summer at a solar longitude ls of 245 11 when mars global surveyor thermal emission spectrometer tes derived near maximum surface temperatures are 296 5 k and mars reconnaissance orbiter mars climate sounder mcs and mars odyssey thermal emission imaging system themis derived mid afternoon surface temperatures are 273 k sml rsl continue to lengthen for 104 38 sols with an average near maximum surface temperature of 298 5 k the sml rsl then stop lengthening at ls 314 12 when mid afternoon surface temperatures drop below 273 k they remain dark for another 116 41 sols until ls 16 14 as surface temperatures continue to fall although the rsl recharge mechanism remains unknown our observation that the vast majority of rsl lengthen only when mid afternoon surface temperatures are 273 k supports the hypothesis that they are formed by shallow subsurface liquid water flows without significant freezing point depression the number and length of rsl at multiple sites increased dramatically following the mars year 28 globe encircling dust storm we interpret this increase to be due to warmer subsurface temperatures created by a dust laden greenhouse effect that may be unique to the southern mid latitudes near ls 270 therefore sml rsl flow is quite sensitive to ground temperature and may only occur under favorable orbital parameters when mean insolation during the rsl lengthening season is above that of the current southern mid latitude mean insolation value this value is currently at a peak that has not been attained for the last 100 ka meanwhile the rsl poor northern mid latitude mean insolation is near a minimum and has a value 27 lower than the southern value if sml rsl are indeed formed by shallow subsurface freshwater flows then they may be some of the best locations on mars to explore for extant life

hydrological characteristics of recurrent slope lineae on mars evidence for liquid flow through regolith and comparisons with antarctic terrestrial analogs abstract on the basis of their morphology and seasonal thermal characteristics recurrent slope lineae rsl on mars have been inferred to be a possible result of the flow of a liquid likely a saline brine through the upper portions of the martian regolith in this note we analyze repeat hirise imaging of rsl to show that the downslope growth rate of recurrent slope lineae is well fit by an elementary groundwater flow model that also describes the downslope propagation of antarctic water tracks terrestrial analogs to rsl and that the apparent permeability of rsl bearing slopes is consistent with the observed sandy regolith substrate

sm nd and rb sr dating of amphibolite from the nellore khammam schist belt se india constraints on the collision of the eastern ghats terrane and dharwar bastar craton the nellore khammam schist belt se india is sandwiched in between the proterozoic eastern ghats terrane and the archaean dharwar bastar craton we report sm nd and rb sr mineral isochron ages of amphibolite from the schist belt the sm nd and rb sr ages are 824 43 ma and 481 16 ma respectively the sm nd age indicates the timing of peak metamorphism whereas the rb sr age indicates the pan african thermal overprint the peak metamorphism was related to collision of the eastern ghats terrane with the dharwar bastar craton which occurred during early neoproterozoic time

the formation and evolution of youthful gullies on mars gullies as the late stage phase of mars most recent ice age gullies are extremely young erosional depositional systems on mars that have been carved by an agent that was likely to have been comprised in part by liquid water malin m c edgett k s 2000 evidence for recent groundwater seepage and surface runoff on mars science 288 2330 2335 mcewen a s et al 2007 a closer look at water related geologic activity on mars science 317 1706 1709 the strong latitude and orientation dependencies that have been documented for gullies require 1 a volatile near the surface and 2 that insolation is an important factor for forming gullies these constraints have led to two categories of interpretations for the source of the volatiles 1 liquid water at depth beneath the melting isotherm that erupts suddenly groundwater and 2 ice at the surface or within the uppermost layer of soil that melts during optimal insolation conditions surface near surface melting in this contribution we synthesize global hemispheric regional and local studies of gullies across mars and outline the criteria that must be met by any successful explanation for the formation of gullies we further document trends in both hemispheres that emphasize the importance of top down melting of recent ice rich deposits and the cold trapping of atmospherically derived h 2o frost snow as important components in the formation of gullies this provides context for the incorporation of high resolution multi spectral and hyper spectral data from the mars reconnaissance orbiter that show that 1 cold trapping of seasonal h 2o frost occurs at the alcove channel level on contemporary mars 2 gullies are episodically active systems 3 gullies preferentially form in the presence of deposits plausibly interpreted as remnants of the late amazonian emplacement of ice rich material and 4 gully channels frequently emanate from the crest of alcoves instead of the base showing that alcove generation is not necessarily a product of undermining and collapse at these locations a prediction of the groundwater model we interpret these various lines of evidence to mean that the majority of gullies on mars are explained by the episodic melting of atmospherically emplaced snow ice under spin axis orbital conditions characteristic of the last several myr

present day impact cratering rate and contemporary gully activity on mars the mars global surveyor mars orbiter camera has acquired data that establish the present day impact cratering rate and document new deposits formed by downslope movement of material in mid latitude gullies on mars twenty impacts created craters 2 to 150 meters in diameter within an area of 21 5 106 square kilometers between may 1999 and march 2006 the values predicted by models that scale the lunar cratering rate to mars are close to the observed rate implying that surfaces devoid of craters are truly young and that as yet unrecognized processes of denudation must be operating the new gully deposits formed since august 1999 are light toned and exhibit attributes expected from emplacement aided by a fluid with the properties of liquid water relatively long extended digitate distal and marginal branches diversion around obstacles and low relief the observations suggest that liquid water flowed on the surface of mars during the past decade

formation of recurring slope lineae by liquid brines on present day mars 1 recurring slope lineae rsl are small scale seasonal flow features identified by mars reconnaissance orbiter that present several interesting characteristics such as an albedo contrast seasonal dependence and a strong preference for equator facing slopes all of these characteristics strongly suggest a thermally driven mechanism such as a liquid triggered or dominated flow here we investigate the possibility that these features are formed by melting of brines of various compositions via a combination of thermodynamic and kinetic numerical models results suggest that a solution with a freezing temperature of 223 k can best reproduce the observed seasonality relatively high surface evaporation rates at the rsl locations make the flows quickly disappear over a single season our model reproduces well the seasonality of rsl and can explain the preference for equator facing slopes suggesting that brine flows and therefore liquids are possible on a small time and space scale today on mars however if the rsl are indeed formed by brines it may indicate that a recharge mechanism is active in order to maintain a source of brine over even short geological timescales which would have important implications for the martian water cycle

present day formation and seasonal evolution of linear dune gullies on mars linear dune gullies are a sub type of martian gullies as their name suggests they only occur on sandy substrates and comprise very long compared to their width straight or sinuous channels with relatively small source areas and almost non existent visible deposits linear dune gullies have never been observed on terrestrial dunes and their formation process on mars is unclear here we present the results of the first systematic survey of these features in mars southern hemisphere and an in depth study of six dunefields where repeat imaging allows us to monitor the changes in these gullies over time this study was undertaken with hirise images at 25 30 cm pix and 1 m pix elevation data derived from hirise stereo images we find the latitudinal distribution and orientation of linear dune gullies broadly consistent with the general population of martian gullies they occur predominantly between 36 3 s and 54 3 s and occasionally between 64 6 s and 70 4 s they are generally oriented toward ssw at bearings between 150 and 260 we find that these gullies are extremely active over the most recent 5 martian years of images activity comprises 1 appearance of new channels 2 lengthening of existing channels 3 complete or partial reactivation and 4 disappearance of gullies we find that gully channels lengthen by 100 m per year the intense activity and the progressive disappearance of linear dune gullies argues against the hypothesis that these are remnant morphologies left over from previous periods of high obliquity millions of years ago the activity of linear dune gullies reoccurs every year between the end of winter and the beginning of spring ls 167 4 216 6 and coincides with the final stages of the sublimation of annual co ice deposit this activity often coincides spatially and temporally with the appearance of recurrent diffusing flows rdfs digitate shaped dark patches with low relative albedo up to 48 lower than the adjacent dune that encompass the active site south and ssw facing dune slopes are those which preferentially host co2 frost deposits however it is only those with angles of 20 just below the crest which possess linear dune gullies suggesting a slope limited formation process these observations provide a wealth of temporal and morphometric data that can be used to undertake numerical modeling to direct future image monitoring and guide laboratory experiments that can be used to better constrain the formation process of these features

topographic measurements of slope streaks on mars abstract slope streaks are enigmatic actively forming albedo features occurring on slopes in high albedo low thermal inertia dust rich equatorial regions on mars they are a specifically martian phenomenon with no direct analogs on the earth their morphology suggests that the streaks are initiated at their upslope tips and propagate down to their termini however the physical mechanism of their formation is uncertain we performed a large series of measurements of slopes associated with slope streaks using stereo pairs of high resolution orbital images obtained by hirise camera and generated several digital elevation models for selected streaks we found that 1 slopes at the upslope streak tips range widely however there is a strong indication that streaks can be initiated only on slopes steeper than 20 2 slopes of the streak termini show an even wider range with some streaks terminating at slopes as steep as their tips while others propagate all the way down to horizontal surfaces 3 the streaks can propagate stably for long many hundreds of meters distances and can turn following the topographic gradient on 10 15 slopes 4 no uphill propagation of streaks is detected over baselines of tens of meters 5 the slope streaks often propagate over 1 2 m high obstacles and can climb 1 2 m uphill over short meters distances we used these findings to assess the viability of two classes of hypotheses about slope streak formation mechanisms proposed earlier 1 dry some kind of run away avalanche like dry granular flow and 2 wet some kind of run away propagation of a front of percolating brines in the shallow subsurface no specific observation unambiguously proves or rejects either of the two mechanisms several of our findings are readily explained by the dry mechanism and cannot be easily explained with any kind of wet mechanism while other findings are closely consistent with the wet mechanism and are difficult to reconcile with the dry mechanism this situation might be explained by equifinality meaning that the streaks despite their similarity are formed by different physical processes alternatively some modifications to either the dry or wet mechanisms may be able to provide a coherent explanation it is also possible that new ideas are needed to understand the processes involved

physical models and predictions for recurring slope lineae formed by wet and dry processes abstract the observation of low albedo elongated and transient features lengthening downhill on mars has attracted wide interest because of the possible role of aqueous fluids in their formation these recurring gravity driven processes called recurring slope lineae rsl remain mysterious in that although the influence of local climate conditions has been established their nature dry versus wet and the mechanisms that govern their growth and fading are debated we present three different physical models for the growth of rsl the first two are wet based models with different aqueous fluid evaporation models and the last is based on dry granular theory we discuss the prediction of each model with regards to the growth and fading of rsl and their morphology we finally discuss the strengths and weaknesses of these models in light of what we currently observe on mars we find that both wet and dry rsl scenario face challenges mostly regarding aspects of mass balance however water based scenarios provide a consistent framework to reconcile the different sets of morphological observations made on rsl

collision tectonics in the late precambrian eastern ghats mobile belt mesoscopic to satellite scale structural observations regional mapping of a section across the eastern ghats mobile belt egmb north of the godavari graben in eastern peninsular india by using landsat thematic mapper data enables recognition of a number of shear zones lineaments and structural domes and basins a conspicuous megashear occurs at the western boundary of the granulite facies rocks of the egmb adjacent to the archean granite greenstone craton the confinement of a suite of alkaline igneous rocks to this shear zone is a notable feature the strike extensions of this shear belt extend through to the elchuru alkaline complex prakasam district andhra pradesh and the syenite plutons of koraput district orissa the contrasting lithologies metamorphism and structural history on either side of the shear zone suggests that it might be a precambrian suture zone the mesoscopic structural features in the egmb include prominent foliation with moderate to steep dips folds faults shears s c fabrics pinch and swell structures and other linear fabric elements these observations favour the consideration of drastic crustal shortening and thickening and a complex deformational sequence the major rock units in this part of egmb comprise garnetiferous sillimanite gneisses quartzites and calc granulites forming the khondalitic suite of rocks and a wide variety of charnockitic rocks the contact of the two rock units is generally sheared and often migmatised the structural fabric suggests two major tectonic events an essentially horizontal tectonic regime resulting in thrust systems and associated structures subsequently followed by strike slip tectonics characterized by high shear strains features such as westward verging thrusts large scale recumbent folds major shear zones structural domes and basins indications of tectonic crustal shortening extensive calc alkali magmatism and widespread migmatization in the region are attributed to collisional processes during proterozoic times the spatial disposition of the egmb and its linkage with the distribution of similar rock units during the late precambrian time in a global tectonic scenario are discussed

the interpretation of the northumberland trough geomagnetic variation anomaly using two dimensional current models summary the electromagnetic fields at the surface are non linear functionals of the electrical conductivity of the earth however the anomalous magnetic fields which are created by lateral variations in the conductivity are linear functionals of the internal current density the inverse problem analysed in this paper is that of using the spatial structure of the vertical field defined along a profile perpendicular to the strike of a 2 d structure to infer the lateral and vertical distribution of current parallel to the strike in the northumberland trough survey magnetometers at some sites are operated simultaneously with a reference instrument at durham and interstation vertical field transfer functions were fitted to the data they are subsequently used to predict the vertical field at each site which is associated with a specific horizontal field at the reference other magnetometers were run separately and only single station transfer functions could be computed these yield predictions of the vertical field which are biased by anomalous horizontal fields when the spatial structure of the anomaly is known the horizontal component of the field can be predicted from the vertical by using the constraint that the field derives from a potential which satisfies the laplace equation the corrections that are required to convert from singlestation to inter station transfer functions can be estimated from the maps of the horizontal field this approach is used to generate vertical field values at sites spaced at 10 km intervals along a 100 km profile traversing the alston block and northumberland trough in northern england the map of the horizontal component anomalies relates more simply to the structure than the vertical component map the surface magnetic fields do not define a unique distribution of current density withm the earth the non uniqueness is removed by fixing the direction and bounding the magnitude of the current density the inversion of the set of constraints is solved by linear programming methods the current density in the carboniferous sedimentary rocks filling the northumberland trough is calculated by combining estimates of their conductivity based on archie s law with measurements of the electric field at a magneto

ultrahigh resolution topographic mapping of mars with mro hirise stereo images meter scale slopes of candidate phoenix landing sites 1 the objectives of this paper are twofold first to report our estimates of the meter to decameter scale topography and slopes of candidate landing sites for the phoenix mission based on analysis of mars global surveyor mgs mars orbiter camera moc images with a typical pixel scale of 3 m and mars reconnaissance orbiter mro high resolution imaging science experiment hirise images at 0 3 m pixel 1 and second to document in detail the geometric calibration software and procedures on which the photogrammetric analysis of hirise data is based a combination of optical design modeling laboratory observations star images and mars images form the basis for software in the u s geological survey integrated software for imagers and spectrometers isis 3 system that corrects the images for a variety of distortions with single pixel or subpixel accuracy corrected images are analyzed in the commercial photogrammetric software socet set bae systems yielding digital topographic models dtms with a grid spacing of 1 m 3 4 pixels that require minimal interactive editing photoclinometry yields dtms with single pixel grid spacing slopes from moc and hirise are comparable throughout the latitude zone of interest and compare favorably with those where past missions have landed successfully only the mars exploration rover mer b site in meridiani planum is smoother moc results at multiple locations have root mean square rms bidirectional slopes of 0 8 4 5 at baselines of 3 10 m hirise stereopairs one per final candidate site and one in the former site yield 1 8 2 8 slopes at 1 m baseline slopes at 1 m from photoclinometry are also in the range 2 3 after correction for image blur slopes exceeding the 16 phoenix safety limit are extremely rare

plate margin paleostress variations and intracontinental deformations in the evolution of the cuddapah basin through proterozoic abstract the sedimentary basins are often influenced by adjoining mobile belts as is the case of the proterozoic cuddapah basin in southern india lying in proximity of the eastern ghats granulite belt egb and the southern granulite terrain sgt two major faults gani kalva and kona faults in the western part of the cuddapah basin have been examined in this work to comment on the changes in paleostress conditions affecting the basin evolution punctuated by several stages of extensional and compressional regimes in the time interval 1 9 0 5 ga the tensor solutions were obtained for the mesoscale faults and fault striae using the improved right dihedron method followed by the rotational optimization method tensor delvaux and sperner 2003 combining the paleostress field reconstruction and other structural stratigraphic attributes we propose a possible scenario of punctuated evolution of the cuddapah basin and its inversion the stress regimes are tentatively correlated with multiple stages of basin opening and deformation of basin in fill representing the pre grenvillian through the pan african orogeny the paleostress conditions derived from various stratigraphic horizons provide an opportunity to comment on the changes in tectonic stresses including several stages of extensional and compressive regimes in the cuddapah basin the tensor solutions were obtained for the mesoscale faults and fault striae in the neighborhood of above two fault lines using the improved right dihedron method followed by the rotational optimization method tensor delvaux and sperner 2003 the most prominent stress states recorded around the two fault lines can be classified into those affecting 1 the paleoproterozoic lower cuddapah successions 2 the younger kurnool group and 3 both the groups integrating the stress states of the fault slip analysis obtained from different unconformity bounded rock groups of lower cuddapah and other geologic data we suggest extensional to transtensive pure strike slip regime to be active during the first phase of basin opening and c 1 89 ga mafic igneous activity late compressional to transpressive pure strike slip regimes are well recorded from the younger kurnool group representing late neoproterozoic deformations the tensor solutions from different unconformity bound stratigraphic horizons constrain different states of deformation we relate the extensional to transtensive pure strike slip regimes from lower cuddapah successions to the ongoing basin opening events and the associated palaeoproterozoic igneous activities the late neoproterozoic to early paleozoic compressional to transpressive strike slip regime present the possible effects of compressional activities happening around the cratonic margin the present analysis lends further support to the idea that estimation of paleostress states from fault slip data even in regions of relatively weak deformation in continental interior are important while assessing influence of plate margin stresses on the continental interior

proterozoic evolution of eastern dharwar and bastar cratons india an overview of the intracratonic basins craton margins and mobile belts abstract based on critical analysis of stratigraphic succesions in the proterozoic intracratonic basins geochronological data and possible connections or disconnections with adjacent fold belts and craton margin mobile belts an overview of the proterozoic evolution of the eastern dharwar and bastar cratons in india is presented the chattisgarh and cuddapah basins in these cratons with archean nuclei host sedimentary successions ranging in age from the paleoproterozoic to the ediacaran period and representing several silicilastic and carbonate cycles the proterozoic successions of the pranhita godavari valley pgv basin along the dharwar bastar join record multiple rifting since late neoarchean suturing of the two cratons we postulate a first order stratigraphic correlation across the cratons and their join and discuss how major sea level fluctuations coupled with regional tectonic events shaped the development of unconformity bound successions adjoining fold belts and the mobile belts with supposed global tectonic connections the oldest paleoproterozoic intracratonic sedimentation is preserved in the cuddapah and pgv basins while sedimentation in the bastar craton is largely mesoproterozoic the fluviodeltaic to shallow marine neoproterozoic sedimentation followed emplacement of end mesoproterozoic kimberlites and lamproites indicating thermal rejuvenation of the indian continental crust the allochthonus nallamalai fold belt in eastern cuddapah basin and the early mesoproterozoic fold belt in pgv basin point to craton margin crustal convergences which punctuated the paleoproterozoic sedimentation widespread development of carbonate bearing sequences in the mesoproterozoic to neoproterozoic successions point to peneplanation of the cratons and stable platformal sedimentation the neoproterozoic sedimentation was terminated following the docking of the eastern ghats belt to the eastern margin of the dharwar bastar ensemble and possible final tectonic hiccups in the central indian tectonic zone bordering the bastar craton the available data and their analysis rule out any foreland basin type connection between the eastern ghats belt and cratonic sedimentation in bastar and eastern dharwar

new and recent gully activity on mars as seen by hirise 1 fresh appearing gully deposits are found at tens of sites in the southern hemisphere of mars these deposits have latitudinal and azimuthal dependences similar to the overall preferences of southern hemisphere gullies suggesting that most gullies can undergo such events definite changes are seen at ten sites including two previously reported these include visible modification of gully channels and aprons those formation intervals constrained to better than one mars year tend to include winter and exclude summer suggesting seasonal activity this seasonal activity is consistent with proposed models for gully formation driven by co2 frost although at least some of the new deposits are probably due to dry granular flow with no volatile involvement as these deposits are capable of effecting distinct topographic changes to gully aprons and channels they represent a significant component of recent gully evolution

are different martian gully morphologies due to different processes on the kaiser dune field we describe and compare the morphology and activity of two types of gullies with different orientations collocated on the kaiser dune field in the southern hemisphere of mars large apron gullies and linear dune gullies the activity of large apron gullies follows an annual cycle i material collapse into the alcove mid autumn late winter as co2 condenses ii remobilization by mass flows late winter and iii continuous appearance of hundreds of digitate flows on the fan autumn winter we find that large apron gullies could form in hundreds of martian years in contrast linear dune gullies are active briefly in late winter when the co2 frost disappears their activity is characterized by the extension of channels the creation of pits and the darkening of the surface linear dune gullies are likely to form within one to tens of martian years we infer that insolation which influences the depth to ground ice and the amount of volatile deposited may be the factor differentiating large apron gullies and linear dune gullies sediment transport by co2 sublimation is a good candidate for the activity observed in all of these features however linear gullies could also be formed by brine release when the temperature rises abruptly after the removal of the co2 ice

alkaline magmatism along the southeastern margin of the indian shield implications for regional geodynamics and constraints on craton eastern ghats belt suturing abstract deformed alkaline complexes at the contact between the eastern ghats belt egb and the archaean cratons in southeastern india mark the location of a collisional suture superimposing an earlier mesoproterozoic 1 5 1 3 ga rift this article offers a plausible geodynamic model explaining the alkaline magmatism and its relationship to regional crustal evolution the mesoproterozoic rift can be correlated to the breakup of the supercontinent columbia and may have opened an ocean between eastern india and east antarctica where the sedimentary sequences of the eastern ghats province egp were deposited between 1 4 and 1 2 ga inversion of the rift basin during the late mesoproterozoic 1 0 ga led to the collision of eastern india with east antarctica during rodinia assembly the collision formed the grenvillian egp rayner complex orogen where the egp sediments and the rocks of the rayner complex were deformed metamorphosed and migmatized at granulite facies condition the mesoproterozoic rifting and grenvillian basin closure may thus represent a wilson cycle related to the breakup of columbia and the assembly of rodinia the craton egb suture was subsequently modified significantly during pan african tectonism 0 5 0 6 ga when the egb granulites were thrust westward over the cratonic foreland along a number of amphibolite facies shear zones at the contact the shearing deformed and metamorphosed the cratonic margin and the alkaline complexes it hosts the thrust stacking in many places has the craton boundary and the alkaline rocks in the footwall and the egb granulites in the hanging wall the continuity of the pan african shear fabric across the craton granulite contact and the lack of grenvillian ages from the alkaline and other craton margin rocks in such regions give the apparent impression that the two crustal segments amalgamated during pan african tectonism and not during the earlier grenvillian collision geodynamic constraints however indicate that this was unlikely and the inconsistency arises because the present crustal geometry exposes only the eroded pan african thrust contact between the craton and the egb and not the original grenvillian suture which may be lying unexposed under the granulite thrust sheets