a noachian source region for the black beauty meteorite and a source lithology for mars surface hydrated dust the martian surface is covered by a fine layer of oxidized dust responsible for its red color in the visible spectral range bibring et al 2006 morris et al 2006 in the near infrared the strongest spectral feature is located between 2 6 and 3 6 m and is ubiquitously observed on the planet jouglet et al 2007 milliken et al 2007 although this absorption has been studied for many decades its exact attribution and its geological and climatic implications remain debated we present new lines of evidence from laboratory experiments orbital and landed missions data and characterization of the unique martian meteorite nwa 7533 all converging toward the prominent role of hydroxylated ferric minerals martian breccias so called black beauty meteorite nwa7034 and its paired stones nwa7533 and nwa 7455 are unique pieces of the martian surface that display abundant evidence of aqueous alteration that occurred on their parent planet agee et al 2013 these dark stones are also unique in the fact that they arose from a near surface level in the noachian southern hemisphere humayun et al 2013 we used ir spectroscopy fe xanes and petrography to identify the mineral hosts of hydrogen in nwa 7533 and compare them with observations of the martian surface and results of laboratory experiments the spectrum of nwa 7533 does not show mafic mineral absorptions making its definite identification difficult through nir remote sensing mapping however its spectra are virtually consistent with a large fraction of the martian highlands abundant nwa 7034 7533 and paired samples lithologies might abound on mars and might play a role in the dust production mechanism

the fate of the submarine ikaite tufa columns in southwest greenland under changing climate conditions abstract ikaite is considered a metastable mineral forming and stable only at low temperatures and therefore an indicator of low temperature carbonate precipitation often associated with cold marine seeps it is found world wide but most spectacularly in ikka fjord in southwest greenland as submarine carbonate tufa columns here ikaite is formed as a result of submarine spring water mixing with cold seawater as ikaite disintegrates at temperatures above 6 7 c it has been speculated that global warming could endanger this unique habitat as well as other sites in ikka fjord in situ water chemistry in and around an ikaite column measured continuously over two years showed that the column water is alkaline ph 9 10 throughout the year with temperatures of 1 3 6 0 c and conductivities of 5 7 7 9 ms cm 1 favoring year round growth of columns at 4 5 cm per month short term in situ measurements with needle micro sensors from both older dehydrated and calcified parts and more recently formed solid parts of an ikaite tufa column showed similar ph and temperature values including a temperature variation over the tidal cycle in the uppermost recently deposited ikaite matrix spring water escaping at the top causes passive drag of seawater into the porous ikaite matrix leading to a mixing layer several centimeters thick that has ph values intermediate to the spring water in the column and the surrounding seawater we conclude that the main part of the columns consisting of fossilized ikaite inverted to calcite partly sealed by calcifying coralline algae and with year round flow of alkaline freshwater through distinct channels are resistant to warming in the more diffuse top part of the columns the formation of ikaite and thus column growth will be limited in the future due to increased fjord water temperature during the

stratigraphy of aeolis dorsa mars stratigraphic context of the great river deposits unraveling the stratigraphic record is the key to understanding ancient climate and past climate changes on mars grotzinger j et al 2011 astrobiology 11 77 87 stratigraphic records of river deposits hold particular promise because rain or snowmelt must exceed infiltration plus evaporation to allow sediment transport by rivers therefore river deposits when placed in stratigraphic order could constrain the number magnitudes and durations of the wettest and presumably most habitable climates in mars history we use crosscutting relationships to establish the stratigraphic context of river and alluvial fan deposits in the aeolis dorsa sedimentary basin 10 e of gale crater at aeolis dorsa wind erosion has exhumed a stratigraphic section of sedimentary rocks consisting of at least four unconformity bounded rock packages recording three or more distinct episodes of surface runoff early deposits 700 m thick are embayed by river deposits 400 m thick which are in turn unconformably draped by fan shaped deposits 900 m thick unconformably drape all previous deposits river deposits embay a dissected landscape formed of sedimentary rock the river deposits are eroding out of at least two distinguishable units there is evidence for pulses of erosion during the interval of river deposition the total interval spanned by river deposits is 1 10 6 2 10 7 yr and this is extended if we include alluvial fan deposits alluvial fan deposits unconformably postdate thrust faults which crosscut the river deposits this relationship suggests a relatively dry interval of 4 10 7 yr after the river deposits formed and before the fan shaped deposits formed based on probability arguments yardang forming layered deposits unconformably postdate all of the earlier deposits they contain rhythmite and their induration suggests a damp or wet near surface environment the time gap between the end of river deposition and the onset of yardang forming layered deposits is constrained to 1 10 8 yr by the high density of impact craters embedded at the unconformity the time gap between the end of alluvial fan deposition and the onset of yardang forming layered deposits was at least long enough for wind induced saltation abrasion to erode 20 30 m into the alluvial fan deposits we correlate the yardang forming layered deposits to the upper layers of gale crater s mound mt sharp aeolis mons and the fan shaped deposits to peace vallis fan in gale crater alternations between periods of low mean obliquity and periods of high mean obliquity may have modulated erosion deposition cycling in aeolis this is consistent with the results from an ensemble of simulations of solar system orbital evolution and the resulting history of the obliquity of mars 57 of our 61 simulations produce one or more intervals of continuously low mean mars obliquity that are long enough to match our aeolis dorsa unconformity data

formation of clays ferrihydrite and possible salts in hydrae chasma mars abstract we used multiple orbital data sets to analyze the morphology composition and stratigraphy of clays and other hydrated deposits within hydrae chasma fe mg smectites are concentrated along the lower floor of the chasma adjacent to pit craters there are at least two distinct smectites that vary in their morphology and spectral properties with a more mg rich smectite associated with a thin brighter upper layered deposit and a more fe rich smectite in a lower darker massive deposit we also identified a younger hydrated unit with spectral features similar to ferrihydrite the spectra of this unit lack an absorption between 2 28 and 2 31 m but display a drop in reflectance near 2 3 m the ferrihydrite type detections correspond to cleaner surfaces of light toned deposits further north and higher in elevation than the smectites a few small outcrops in the southern chasma floor appear brighter than the clays and display an additional narrow absorption at 2 4 m in combination with the smectite features which may indicate a smectite plus perchlorate mixture there are no valleys along the plateau that intersect hydrae chasma and consequently any water that created the fe mg smectites and ferrihydrite must have been from groundwater in the subsurface or surface water sourced from within the chasma a terraced fan and associated valley to the north of the clays provide support for melting snow ice within the chasma and this same water may have also altered materials lower in elevation where the ferrihydrite bearing unit formed under colder conditions than the smectites the change in stratigraphy from smectites to ferrihydrite is consistent with a decrease in global temperature during the hesperian

hydrated silicate minerals on mars observed by the mars reconnaissance orbiter crism instrument phyllosilicates a class of hydrous mineral first definitively identified on mars by the omega observatoire pour la mineralogie l eau les glaces et l activitie instrument preserve a record of the interaction of water with rocks on mars global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy fe mg and al smectite clays this was interpreted to indicate that phyllosilicate formation occurred during the noachian the earliest geological era of mars and that the conditions necessary for phyllosilicate formation moderate to high ph and high water activity were specific to surface environments during the earliest era of mars s history here we report results from the compact reconnaissance imaging spectrometer for mars crism of phyllosilicate rich regions we expand the diversity of phyllosilicate mineralogy with the identification of kaolinite chlorite and illite or muscovite and a new class of hydrated silicate hydrated silica we observe diverse fe mg oh phyllosilicates and find that smectites such as nontronite and saponite are the most common but chlorites are also present in some locations stratigraphic relationships in the nili fossae region show olivine rich materials overlying phyllosilicate bearing units indicating the cessation of aqueous alteration before emplacement of the olivine bearing unit hundreds of detections of fe mg phyllosilicate in rims ejecta and central peaks of craters in the southern highland noachian cratered terrain indicate excavation of altered crust from depth we also find phyllosilicate in sedimentary deposits clearly laid by water these results point to a rich diversity of noachian environments conducive to habitability

groundwater controlled valley networks and the decline of surface runoff on early mars 1 fluvial erosion on early mars was dominated by valley networks created through a combination of groundwater processes and surface runoff a reduced greenhouse effect due to co 2 loss together with a declining geothermal heat flux promoted the growth of a cryosphere and a hesperian hydrologic regime dominated by outflow channel formation we test the hypothesis that the transition from valley network to outflow channel formation was preceded by a more subtle evolution characterized by a weakening of surface runoff leaving groundwater processes as the dominant final source of valley network erosion our hypothesis supported by a terrestrial analog in the atacama desert of chile is related to the groundwater sapping reactivation hypothesis for densely dissecting highland valley networks on mars suggested by baker and partridge in 1986 and focuses on the age analysis of large sparsely dissecting valley networks such as nanedi valles nirgal vallis valleys in fretted terrain and tributaries of outflow channels and valles marineris chasmata we find that these features are consistently late noachian to hesperian in age younger than noachian densely dissecting dendritic valley networks in the southern highlands in the tharsis region the observation of dense and sparse valley network morphologies on hesperian terrain suggests that while surface runoff gave way to groundwater processes consistent with our hypothesis the transition may have occurred later than elsewhere on the planet the volcanic nature of tharsis suggests that geothermal heat and volatile production led to episodically higher volumes of surface runoff in this region during the hesperian

new models for the origin of valles marineris closed depressions current models for the formation of the abundant large closed depressions of valles marineris have serious shortcomings purely tectonic mechanisms are inconsistent with the morphology of many depressions and removal of large quantities of ground ice from the canyon walls is inconsistent with the observed strength of the walls accordingly we offer some alternatives one possibility involves decay of ice rich bodies occupying partially sediment choked ancient graben that predated the overlying cratered and ridged plains other possibilities involve the removal of massive equatorial carbonate deposits storing much of the planet s co2 inventory generated during greenhouse conditions on early mars solution by carbonic acid derived from the atmosphere analogous to terrestrial karst requires extensive recycling of the available water supply solution by various groundwater acids possibly derived from the tharsis magmas requires less water especially if only the smaller closed depressions are due to carbonate decay alternatively volume loss due to decarbonation of carbonate during early high heat flow or a later tharsis related heat pulse can produce extensive collapse especially if the carbonates have high silica content

landscape formation at the deuteronilus contact in southern isidis planitia mars implications for an isidis sea abstract two of the most widely studied landforms that are associated with a putative ocean that filled the northern hemisphere of mars are 1 the vastitas borealis formation vbf plain units that cover a larger portion of the northern lowlands of mars and 2 a candidate paleoshoreline e g the deuteronilus contact which represents the outer margin of the vbf the vbf and the deuteronilus contact are interpreted to result from a short lived late hesperian ocean that readily froze and sublimated similar landforms are also present in the impact basin of isidis planitia and suggest formation processes comparable to those that formed the vbf and the deuteronilus contact in the northern lowlands our study of the deuteronilus contact in isidis revealed geologic evidence that possibly supports the existence of a late hesperian early amazonian isidis sea for example numerous valleys that are incised into the plains of the southern isidis basin rim between 82 90 e and 3 6 n and trend a few tens of kilometers to the north following the general topographic gradient toward the center of isidis planitia a few of them reach the deuteronilus contact and continue as sinuous ridges in the isidis interior plains iip based on our findings we conclude that the geologic setting along the deuteronilus contact including the valleys and ridges is a result of 1 late hesperian short term fluvial activity 2 a late hesperian early amazonian short lived isidis sea that readily froze 3 subglacial drainage and esker formation and 4 subsequent sublimation of the proposed isidis ice sheet although the fluvio glacial model we introduce in our manuscript cannot fully explain the geologic setting possible alternative formation models including relief inversion and fluvio volcanic scenarios are even less capable in explaining the observed geologic setting along the deuteronilus contact

sublacustrine depositional fans in southwest melas chasma two depositional fan complexes have been identified on the floor of southwest melas chasma the western fan complex is located near the center of an enclosed basin in southwest melas chasma and is composed of multiple lobes with dendritic finger like terminations these fans are very flat and have a morphology unlike any other fan that has been previously identified on mars on the basis of the morphologic similarity of the western fan complex to the mississippi submarine fan complex we suggest that it may be a deep subaqueous fan depositional system there are numerous channels on the surface of the western fan complex and measurements of channel length width and sinuosity are consistent with channels observed on terrestrial submarine fans the eastern melas depositional fans are less well preserved and may be of deltaic or sublacustrine origin recognition of the fans supports earlier suggestions for the presence of a former lake in melas chasma and indicates that a significant body of water was present and stable at the surface of mars for at least 10 2 to 10 4 years

topography of valles marineris implications for erosional and structural history compilation of a simplified geologic geomorphic map onto digital terrain models of the valles marineris permitted an evaluation of elevations in the vicinity of the troughs and the calculation of depth of troughs below surrounding plateaus thickness of deposits inside the troughs volumes of void spaces above geologic geomorphic units and volumes of deposits the central troughs north ophir north and central candor and north melas chasmata lie as much as 11 km below the adjacent plateaus in ophir and candor chasmata interior layered deposits reach 8 km in elevation if the deposits are lacustrine and if all troughs were interconnected lake waters standing 8 km high would have spilled out of coprates chasma onto the surrounding plateaus having surface elevations of only 4 5 km in this case interior deposits above about 4 km in the central troughs would not be lacustrine they could be volcanic on the other hand the troughs may not have been interconnected at the time of interior deposit emplacement they may have formed isolated ancestral basins the existence of such basins is supported by independent structural and stratigraphic evidence the ancestral basins may have eventually merged perhaps through renewed faulting to form northern subsidiary troughs in ophir and candor chasmata and the coprates north melas ius graben system the peripheral troughs are only 2 5 km deep shallower than the central troughs they may have formed from a combination of erosional collapse and structural activity chaotic terrain is seen in the peripheral troughs near a common contour level of about 4 km on the adjacent plateaus which supports the idea of release of water under artesian pressure from confined aquifers the layered deposits in the peripheral troughs may have formed in isolated depressions that harbored lakes and predated the formation of the deep outflow channels if these layered deposits are of volcanic origin they may have been emplaced beneath ice in the manner of table mountains areal and volumetric computations show that erosion widened the troughs by about one third and that deposits occupy one sixth of the interior space even though the volume eroded is larger than the volume deposited topographic and geologic considerations imply that material eroded from trough walls was probably part of the interior layered deposits but not their sole source additional material may have come from subterranean piping from reworking of local disintegration products on the floors such as chaotic materials or from eolian influx but overall it is likely that the additional material is volcanic and that it forms mostly the upper more diversely bedded layers of the interior deposits

layering in the wall rock of valles marineris intrusive and extrusive magmatism 1 high resolution images of the walls exposed in valles marineris reveal variations in appearance and degree of layering indicating various lithologies comprise the tharsis plateau the layered wall rock has been proposed to result from effusive flood basalt volcanism or interbedded sediments and volcanics we present observations of unlayered rock that indicate layering extends to a greater depth in the western half of valles marineris and is confined to the tharsis plateau a region of thickened uplifted crust resulting from prolonged intrusive activity consistent with this view we propose that the observed layering may be a manifestation of intrusive rocks resulting from crystal fractionation of intruded basaltic magmas terrestrial layered plutons provide analogs for comparison such as those of the north atlantic igneous province naip a large igneous province associated with crustal rifting and exposures of thick sequences of layered flood basalts and intruded layered cumulates index terms 5480 planetology solid surface planets volcanism 8450 6225 planetology solar system objects mars 8450 volcanology planetary volcanism 5480 citation williams j p d a paige and c e manning layering in the wall rock of valles marineris intrusive and extrusive magmatism geophys res lett 30 12 1623 doi 10 1029 2003gl017662 2003

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

light toned strata and inverted channels adjacent to juventae and ganges chasmata mars 1 light toned layered deposits on the plains adjacent to juventae and ganges chasmata have been identified and analyzed with several instruments onboard the mars reconnaissance orbiter including hirise ctx and crism beds exhibit variations in brightness color polygonal fracturing and erosional properties that are not seen in light toned layered deposits within the chasmata at both juventae and ganges the light toned layered deposits along the plains have associated features we interpret as fluvial including sinuous ridges inverted channels that exhibit light toned layering and an extensive valley system for the ganges deposit the strong correlation between the inverted channels and light toned layered deposits suggests an association with fluvial lacustrine processes although pyroclastic and eolian activity may also be involved in their emplacement the identification of potential fluvial lacustrine layered deposits and associated valley networks suggests surface water flow in the valles marineris region that occurred for sustained periods during the hesperian 3 7 3 0 gyr

plateaus and sinuous ridges as the fingerprints of lava flow inflation in the eastern tharsis plains of mars abstract the tharsis montes rift aprons are composed of outpourings of lava from chaotic terrains to the northeast and southwest flank of each volcano sinuous and branching channel networks that are present on the rift aprons suggest the possibility of fluvial processes in their development or erosion by rapidly emplaced lavas but the style of lava flow emplacement throughout rift apron development is not clearly understood to better characterize the style of lava emplacement and role of fluvial processes in rift apron development we conducted morphological mapping of the pavonis mons southwest rift apron and the eastern tharsis plains using images from the high resolution imaging science experiment hirise mars orbiter camera moc context camera ctx thermal emission imaging system themis and high resolution stereo camera hrsc along with the mars orbiter laser altimeter mola precision experiment data records pedrs and gridded data our approach was to 1 search for depositional fans at the slope break between the rift apron and adjacent low slope plains 2 determine if there is evidence that previously formed deposits might have been buried by plains units 3 characterize the tharsis plains morphologies east of pavonis mons and 4 assess their relationship to the rift apron units we have not identified topographically significant depositional fans nor did we observe evidence to suggest that plains units have buried older rift apron units flow features associated with the rift apron are observed to continue across the slope break onto the plains in this area the plains are composed of a variety of small fissures and low shield vents around which broad channel fed and tube fed flows have been identified we also find broad flat topped plateaus and sinuous ridges mixed among the channels tubes and vents flat topped plateaus and sinuous ridges are morphologies that are analogous to those observed on the coastal plain of hawai i where lava flows have advanced from the volcano s several degree flank onto the nearly zero degree coastal plain when local volumetric flow rates are low flow fronts tend to spread laterally and often thicken via endogenous growth or inflation of the sheet like flow units if flow advance is restricted by existing topography into narrow pathways inflation can be focused into sinuous elongate ridges the presence of plateaus and ridges emplaced from the rift zones across the plains to the east of pavonis mons and a lack of fan like features or evidence for their burial are consistent with rift apron lavas crossing a slope break with low local volumetric flow rates that led to inflation of sheet like and tube fed lava flows

the high resolution imaging science experiment hirise during mro s primary science phase psp the high resolution imaging science experiment hirise on the mars reconnaissance orbiter mro acquired 8 terapixels of data in 9137 images of mars between october 2006 and december 2008 covering 0 55 of the surface images are typically 5 6 km wide with 3 color coverage over the central 20 of the swath and their scales usually range from 25 to 60 cm pixel nine hundred and sixty stereo pairs were acquired and more than 50 digital terrain models dtms completed these data have led to some of the most significant science results new methods to measure and correct distortions due to pointing jitter facilitate topographic and change detection studies at sub meter scales recent results address noachian bedrock stratigraphy fluvially deposited fans in craters and in or near valles marineris groundwater flow in fractures and porous media quasi periodic layering in polar and non polar deposits tectonic history of west candor chasma geometry of clay rich deposits near and within mawrth vallis dynamics of flood lavas in the cerberus palus region evidence for pyroclastic deposits columnar jointing in lava flows recent collapse pits evidence for water in well preserved impact craters newly discovered large rayed craters and glacial and periglacial processes of particular interest are ongoing processes such as those driven by the wind impact cratering avalanches of dust and or frost relatively bright deposits on steep gullied slopes and the dynamic seasonal processes over polar regions hirise has acquired hundreds of large images of past present and potential future landing sites and has contributed to scientific and engineering studies of those sites warming the focal plane electronics prior to imaging has mitigated an instrument anomaly that produces bad data under cold operating conditions

opaline silica in young deposits on mars high spatial and spectral resolution reflectance data acquired by the mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars crism instrument reveal the presence of h 2o and sioh bearing phases on the martian surface the spectra are most consistent with opaline silica and glass altered to various degrees confirming predictions based on geochernicall experiments and models that amorphous silica should be a common weathering product of the basaltic martian crust these materials are associated with hydrated fe sulfates including h 3o bearing jarosite and are found in finely stratified deposits exposed on the floor of and on the plains surrounding the valles marineris canyon system stratigraphic relationships place the formation age of these deposits in the late hesperian or possibly the amazonian implying that aqueous alteration continued to be an important and regionally extensive process on mars during that time

fluvial and lacustrine activity on layered deposits in melas chasma valles marineris mars 1 valley networks on mars are the most obvious features attesting that different geologic processes and possibly climatic conditions existed in the past themis images reveal valley networks within melas chasma in valles marineris a hesperian age canyon system the valley networks in melas chasma are dense and highly organized and the heads of the valleys are scattered at different elevations all these features suggest that the networks were fed by precipitation the morphological details reveal inner channels on some valley floors attesting that water flowed within these valleys on the dem the valleys flow into a completely enclosed depression the edge of this feature follows a mola contour line and the depression shows many sedimentary morphologies suggesting lacustrine environment these landforms are located on remnants of layered deposits possibly composed of sulfate layers suggesting that fluvial activity could have contributed to the erosion of the layered terrains in valles marineris collectively the features in melas chasma are a maximum of hesperian in age these results suggest that warm wet environmental conditions on mars persisted through the hesperian and were present during the formation of valles marineris the evidence for a paleolake in melas chasma attests to adequate environmental conditions for life development through the hesperian period

interior trough deposits on mars subice volcanoes widespread several kilometer thick successions of layered deposits occur as mounds that partly fill the troughs or chasmata that compose the valles marineris on mars like terrestrial subice volcanoes the layered deposits occur in a volcano tectonic setting within basins that may have held ponded water or ice on the basis of their dimensions morphologies and associated catastrophic floods and other geologic events as shown in viking and new mars global surveyor mgs data sets we suggest that the interior deposits are volcanic in origin and possibly generated by subice eruptions a tuya origin for the mounds can explain the lack of external sediment mound heights that can rival the plateau local flat topped mesas morphologically distinct mounds of different ages horizontal to steep dips fine grained materials indications of rare volcanic vents and lava flows and spectral composition the extremely diverse layering of west candor chasma and possible volcanic cones in melas may have formed by related subaerial eruptions consistent with the suggestion that interior deposits are eroding out of the wall rock some deposits could have been erupted from sites along the walls

mineralogy of juventae chasma sulfates in the light toned mounds mafic minerals in the bedrock and hydrated silica and hydroxylated ferric sulfate on the plateau 1 juventae chasma contains four light toned sulfate bearing mounds denoted here as a d from west to east inside the trough mafic outcrops at the base of the mounds and in the wall rock and light toned layered deposits of opal and ferric sulfates on the plateau hyperspectral visible near infrared compact reconnaissance imaging spectrometer for mars crism spectra were used to identify monohydrated and polyhydrated sulfate phs outcrops of layered material on the bright mounds most of the monohydrated sulfate signatures closely resemble those of szomolnokite feso4 h2o characterized by a water band near 2 08 m while some areas exhibit spectral features more similar to those of kieserite mgso4 h2o with a band centered closer to 2 13 m the largest phs outcrops occur on the top of mound b and their spectral features are most consistent with ferricopiapite melanterite and starkeyite but a specific mineral cannot be uniquely identified at this time coordinated analyses of crism maps mars orbiter laser altimeter elevations and high resolution imaging science experiment images suggest that mounds a and b may have formed together and then eroded into separate mounds while mounds c and d likely formed separately mafic minerals low ca pyroxene high ca pyroxene and olivine are observed in large 2 10 km wide outcrops in the wall rock and in smaller outcrops 50 500 m across at the floor of the canyon most of the wall rock is covered by at least a thin layer of dust and does not exhibit strong features characteristic of these minerals the plateau region northwest of juventae chasma is characterized by an abundance of light toned layered deposits one region contains two spectrally unique phases exhibiting a highly stratified terraced pattern crism spectra of one unit eroded into swirling patterns with arc like ridges exhibit a narrow 2 23 m band assigned to hydroxylated ferric sulfate a thin layer of a fractured material bearing an opaline silica phase is observed at the contact between the older plateau unit and the younger hydroxylated ferric sulfate bearing light toned layered deposits hydrothermal processes may have produced an acidic environment that fostered formation of the hydrated silica and hydroxylated ferric sulfate units

explosive volcanism in the tharsis region global evidence in the martian geologic record 1 a global equatorial set of layered deposits on mars has been reexamined with mars global surveyor data the stratigraphy morphology and erosional characteristics of units separated by thousands of kilometers are remarkably similar to each other and consistent with a widespread episodic subaerial source of fine grained material this study is the first to propose a genetic link between many units that have traditionally been considered on a local or regional level including the medusae fossae formation valles marineris interior deposits chaotic terrain terra meridiani and arabia materials mapping relationships suggest that all of these units are post noachian in age and formation may have continued until the recent past thinning of deposits with increasing distance from the tharsis rise suggests that much of these materials may be volcanic ash flows and air fall from explosive eruptions in the tharsis region analogous to those produced by terrestrial plinian eruptions contemporary martian winds would preferentially transport ash from an eruption plume near tharsis east or west along the equator depending on the season erosion has removed much of the original volcanic ash and only isolated layered stacks remain sometimes in topographic depressions that inhibit erosion modeling indicates that widespread dispersion of ash after an eruption is easily attainable in present or past atmospheric conditions consistent with the hypothesis that the far reaching deposits may be composed of ash from past explosive eruptions in the vicinity of tharsis

martian layered fluvial deposits implications for noachian climate scenarios 1 fluvial deposits in a basin north of holden crater exhibiting a sinuous anabranching pattern are of deltaic or fan origin channel width and meander wavelength indicate persistent flow magnitudes of about 700 m3 s if these flows were produced by quasi periodic climate episodes involving typical terrestrial style precipitation the deposit required thousands to millions of years to accumulate however a scenario of deposition during a few short episodes of constant heavy precipitation resulting from large impacts cannot be excluded

geomorphic study of fluvial landforms on the northern valles marineris plateau mars 1 fluvial landforms are observed on the plateau near echus chasma and other locations on the valles marineris plateau using high resolution 10 to 50 m pixel mars express images and topography branching valleys have a 20 to 100 m deep v shape profile typical of fluvial processes their incision occurred in a thin 150 m and weak dark unit that overlies the plateau basement the valleys are distributed close to watershed boundaries as expected for overland flows and different from pure glacial or hydrothermal processes the 2d geometry of valley networks show drainage densities reaching 1 3 km 1 that indicate a strong 2d extension stage that usually requires a minimum of thousands of years as established from terrestrial examples however the 3d valley geometry shows a limited incision and a lack of concavity suggesting a limited development in time millions of years of evolution are unlikely many outlets connect to the heads of canyons of echus chasma that might involve sapping processes these canyons might have formed coevally with shallow valleys their difference in geometry is a consequence of the difference in lithology which induced a difference in the erosion capacity and an enhanced infiltration conducing to sapping valleys are submitted to modification by aeolian processes sometimes leading to the formation of inverted channels as observed more broadly through the region these landforms formed late in the early mars history and might be considered as examples of episodic fluvial events due to short term climate changes and or regional fluvial activity after the noachian

layered megablocks in the central uplifts of impact craters abstract a database of bedrock exposed in crater central uplifts has been compiled from multiple orbital datasets in this study we focus on uplifts which show decameter scale layers within the exposed megablocks derived from the bedrock of the preexisting target this distinctive morphology found in 41 craters globally occurs mostly in regions mapped as hesperian plains material generally interpreted as regions of extensive flood lavas the association with volcanic units coupled with morphology and mineralogy that is consistent with flood lava emplacement suggests that the layers are stacks of dense lava interbedded with weaker materials estimates for the uplift of stratigraphic sections coupled with morphologic and morphometric analyses lead to estimated thicknesses of the layered unit these estimates indicate hesperian flood lavas are 23 thicker than a previous minimum estimate with a volume of 5 5 10 7 km 3 this increases the known extrusive volcanic production for the history of mars and volatile release to past martian atmospheres

light toned layered deposits in juventae chasma mars abstract we examine hypotheses for the formation of light toned layered deposits in juventae chasma using a combination of data from mars global surveyor s mars orbiter camera moc mars orbiter laser altimeter mola and thermal emission spectrometer tes as well as mars odyssey s thermal emission imaging system themis we divide juventae chasma into geomorphic units of i chasm wall rock ii heavily cratered hummocky terrain iii a mobile and largely crater free sand sheet on the chasm floor iv light toned layered outcrop llo material and v chaotic terrain using surface temperatures derived from themis infrared data and slopes from mola we derive maps of thermal inertia which are consistent with the geomorphic units that we identify llo thermal inertias range from 400 to 850 j m 2 k 1 s 1 2 light toned layered outcrops are distributed over a remarkably wide elevation range 5 8 km from the chasm floor to the adjacent plateau surface geomorphic features the absence of small craters and high thermal inertia show that the llos are composed of sedimentary rock that is eroding relatively rapidly in the present epoch we also present evidence for exhumation of llo material from the west wall of the chasm within chaotic and hummocky terrains and within a small depression in the adjacent plateau the data imply that at least some of the llo material was deposited long before the adjacent hesperian plateau basalts and that juventae chasma underwent and may still be undergoing enlargement along its west wall due to wall rock collapse chaotic terrain evolution and exposure and removal of llo material the new data allow us to reassess possible origins of the llos gypsum one of the minerals reported elsewhere as found in juventae chasma llo material forms only at low temperatures 60 c and thus excludes a volcanic origin instead the data are consistent with either multiple occurrences of lacustrine or airfall deposition over an extended period of time prior to emplacement of hesperian lava flows on the plateau above the chasm

testing evidence of recent hydration state change in sulfates on mars the east candor interior layered deposit ild has signatures of mono and polyhydrated sulfate in alternating layers that give insight into the processes which formed these layered deposits and on the environmental conditions acting on them since then we use orbital data to explore multiple hypotheses for how these deposits formed 1 sulfate bearing ilds experience hydration changes on seasonal to a few years timescales under current mars environmental conditions 2 the deposits experience hydration under recent mars conditions but require the wetter climate of high obliquity and 3 the kieserite could be an original or diagenetic part of a complex evaporite mineral assemblage modeled climatology shows recent mars environmental conditions might pass between multiple sulfate fields however comparison of observatoire pour la mineralogie l eau les glaces et l activite omega and compact reconnaissance imaging spectrometer crism observations of the same ild do not show changes in hydration over 2 mars years low temperatures might slow the kinetics of that transition it is likely that more clement conditions during periods of high obliquity are needed to overcome mineral metastability and hydrate kieserite bearing deposits we find the alternate model that the deposit is a cyclic evaporite sequence of mono and polyhydrated sulfates also plausible but with an unexplained dearth of fe sulfates

origin of the valley networks on mars a hydrological perspective abstract the geomorphology of the martian valley networks is examined from a hydrological perspective for the compatibility with an origin by rainfall globally higher heat flow and localized hydrothermal systems comparison of morphology and spatial distribution of valleys on geologic surfaces with terrestrial fluvial valleys suggests that most martian valleys are probably not indicative of a rainfall origin nor are they indicative of formation by an early global uniformly higher heat flow in general valleys are not uniformly distributed within geologic surface materials as are terrestrial fluvial valleys valleys tend to form either as isolated systems or in clusters on a geologic surface unit leaving large expanses of the unit virtually untouched by erosion with the exception of fluvial valleys on some volcanoes most martian valleys exhibit a sapping morphology and do not appear to have formed along with those that exhibit runoff morphology in contrast terrestrial sapping valleys form from and along with runoff valleys the isolated or clustered distribution of valleys suggests localized water sources were important in drainage development persistent groundwater outflow driven by localized but vigorous hydrothermal circulation associated with magmatism volcanism impacts or tectonism is however consistent with valley morphology and distribution snowfall from sublimating ice covered lakes or seas may have provided an atmospheric source of water for the formation of some valleys in regions where the surface is easily eroded and where localized geothermal hydrothermal activity is sufficient to melt accumulated snowpacks

a field guide to finding fossils on mars the martian surface is cold dry exposed to biologically harmful radiation and apparently barren today nevertheless there is clear geological evidence for warmer wetter intervals in the past that could have supported life at or near the surface this evidence has motivated national aeronautics and space administration and european space agency to prioritize the search for any remains or traces of organisms from early mars in forthcoming missions informed by 1 stratigraphic mineralogical and geochemical data collected by previous and current missions 2 earth s fossil record and 3 experimental studies of organic decay and preservation we here consider whether how and where fossils and isotopic biosignatures could have been preserved in the depositional environments and mineralizing media thought to have been present in habitable settings on early mars we conclude that noachian hesperian fe bearing clay rich fluvio lacustrine siliciclastic deposits especially where enriched in silica currently represent the most promising and best understood astropaleontological targets siliceous sinters would also be an excellent target but their presence on mars awaits confirmation more work is needed to improve our understanding of fossil preservation in the context of other environments specific to mars particularly within evaporative salts and pore fracture filling subsurface minerals

high outflow channels on mars indicate hesperian recharge at low latitudes and the presence of canyon lakes abstract a number of martian outflow channels were carved by discharges from large dilational fault zones these channels were sourced by groundwater not surface water and when observed on high standing plateaus they provide indicators of elevated paleo groundwater levels we identify three outflow channels of hesperian age that issued from a 750 km long fault zone extending from candor chasma to ganges chasma two of these channels allegheny vallis and walla walla vallis have sources 2500 m above the topographic datum too high to be explained by discharge from a global aquifer that was recharged solely in the south polar region the indicated groundwater levels likely required regional sources of recharge at low latitudes the floodwaters that erupted from ophir cavus to form allegheny vallis encountered two ridges that restricted the flow forming temporary lakes the flow probably breached or overtopped these obstructions quickly catastrophically draining the lakes and carving several scablands after the last obstacle had been breached a single main channel formed that captured all subsequent flow we performed hydrologic analyses of this intermediate phase of the flooding prior to incision of the channel to its present depth using floodwater depths of 30 60 m we calculated flow velocities of 6 15 m s 1 and discharges in the range of 0 7 3 10 6 m 3 s 1 locally higher flow velocities and discharges likely occurred when the transient lakes were drained variable erosion at the channel and scabland crossing of mola pass 10644 suggests that the upper 25 30 m may consist of poorly consolidated surface materials underlain by more cohesive bedrock we infer that an ice covered lake with a surface elevation 2500 m probably existed in eastern candor chasma because this canyon is intersected by the ophir catenae fault system from which allegheny vallis and walla walla vallis originated we introduce a new hydrology concept for mars in which the groundwater system was augmented by recharge from canyon lakes that were formed when water was released by catastrophic melting of former ice sheets in tharsis by effusions of flood basalts this model could help to reconcile the expected presence of a thick cryosphere during the hesperian with the abundant evidence for groundwater as a source for some of the circum chryse outflow channels

relative age of interior layered deposits in southwest candor chasma based on high resolution structural mapping high resolution topography generated from stereo hirise high resolution imaging science experiment imagery reveals the meter scale structure of interior layered deposits ild in southwest candor chasma this study seeks to determine the age of the local ild relative to any normal faults that can be attributed to chasma formation the study area is located near the contact of these ild and the wall rock and is in an area where chasma forming normal faults have been proposed we find that while normal faults are found in the study area these faults are not sufficiently large nor appropriately located or oriented to accommodate the roughly northeast southwest extension that is required for normal faults that can be attributed to chasma formation additionally bedding exposed in the local ild generally dips toward the center of candor chasma consistent with sediment deposition in a preexisting basin further pit craters of tithonia catena presumed to predate or be contemporaneous with the formation of west candor chasma do not cut into the ild within the study area these independent lines of evidence support a postchasma age for the ild exposed within the study area chasma related normal faults may exist within these ild at depth but are not exposed at the surface approximately 2 km of conformable stratigraphy is exposed in the study area and therefore at least several kilometers of the local ild were deposited subsequent to any chasma related normal faulting that may have occurred in this part of candor chasma

evidence for persistent flow and aqueous sedimentation on early mars landforms representative of sedimentary processes and environments that occurred early in martian history have been recognized in mars global surveyor mars orbiter camera and mars odyssey thermal emission imaging system images evidence of distributary channelized flow in particular flow that lasted long enough to foster meandering and the resulting deposition of a fan shaped apron of debris indicate persistent flow conditions and formation of at least some large intracrater layered sedimentary sequences within fluvial and potentially lacustrine environments

stratigraphy and erosional landforms of layered deposits in valles marineris mars the complex stratigraphy of layered deposits suggests a diversity of origins ages and post depositional modification histories the complexities within some layered deposits indicate changes in the dominant source materials in space and time the stratigraphy of layered deposits in the isolated martian chasmata hebes juventae and gangis is not well correlated this indicates that at least these chasmata had isolated depositional environments resulting in different stratigraphic sequences separated layered deposits in ophir candor and melas chasmata might have been a single continuous deposit in each chasma chaotic terrains are found in conjunction with layered deposits in juventae gangis and capri eos chasmata in these chasmata layered deposits unconformably overlie chaotic terrains chaotic terrain formation may have provided water to form paleolakes and lacustrine deposition of thick layered deposits may have occurred if the canyons were closed a very thick sequence of the layered deposits has been exposed by erosion a combination of gradual processes such as evaporation of ice and eolian and fluvial transport in addition to structural processes may be responsible for this erosion another alternative is that catastrophic water release under the layered deposits disrupted and initiated erosion of the layered deposits newly identified units of anomalous color are confined to the depressions or reentrants in western candor chasma the difference in color between these units and the surrounding terrain is most consistent with a somewhat greater content of bulk crystalline hematite in these anomalous units the presence of the candor units is a result of original and or secondary deposition which is different from the primary and dominant formation of the layered deposits

the evolution of lacustrine environments on mars is mars only hydrologically dormant abstract this study surveys the evolution of martian impact crater paleolakes through time by establishing their age comparing their locations and describing the formation of lacustrine sedimentary structures and features over time we explore their meaning in terms of global climate changes but also on local and regional scales we observe a co location between recent impact crater paleolakes and regions where gcm modeling shows that mars is currently experiencing days above triple point and below boiling point of water some source areas show morphologies that could be consistent with ancient glacier features in the argyre basin darwin crater region in locations that are also consistent with gcm models of past snow precipitation on mars we propose that at least for some paleolakes our results are best explained by recent and abundant aqueous activity on mars with some meteorological contribution these results are supported by other recent findings on martian meteorite ages by the analysis of new mgs data showing recent volcanic and fluvial activity and by climate modeling they point toward the possibility that mars currently is only hydrologically dormant and that there is a potential for hydrological activity to be generated again in the future following changes in the planet s orbital parameters

stepped fans and facies equivalent phyllosilicates in coprates catena mars stepped fan deposits and phyllosilicate mineralogies are relatively common features on mars but have not previously been found in association with each other both of these features are widely accepted to be the result of aqueous processes but the assumed role and nature of any water varies in this study we have investigated two stepped fan deposits in coprates catena mars which have a genetic link to light toned material that is rich in fe mg phyllosilicate phases although of different sizes and in separate but adjacent trough like depressions we identify similar features at these stepped fans and phyllosilicates that are indicative of similar formation conditions and processes our observations of the overall geomorphology mineralogy and chronology of these features are consistent with a two stage formation process whereby deposition in the troughs first occurs into shallow standing water or playas forming fluvial or alluvial fans that terminate in delta deposits and interfinger with interpreted lacustrine facies with a later period of deposition under sub aerial conditions forming alluvial fan deposits we suggest that the distinctive stepped appearance of these fans is the result of aeolian erosion and is not a primary depositional feature this combined formation framework for stepped fans and phyllosilicates can also explain other similar features on mars and adds to the growing evidence of fluvial activity in the equatorial region of mars during the hesperian and amazonian

mars reconnaissance orbiter observations of light toned layered deposits and associated fluvial landforms on the plateaus adjacent to valles marineris abstract we have used data from the mars reconnaissance orbiter to study 30 80 m thick light toned layered deposits on the plateaus adjacent to valles marineris at five locations 1 south of ius chasma 2 south of western melas chasma 3 south of western candor chasma 4 west of juventae chasma and 5 west of ganges chasma the beds within these deposits have unique variations in brightness color mineralogy and erosional properties that are not typically observed in light toned layered deposits within valles marineris or many other equatorial areas on mars reflectance spectra indicate these deposits contain opaline silica and fe sulfates consistent with low temperature acidic aqueous alteration of basaltic materials we have found valley or channel systems associated with the layered deposits at all five locations and the volcanic plains adjacent to juventae ius and ganges exhibit inverted channels composed of light toned beds valleys channels and light toned layering along the walls of juventae and melas chasmata are most likely coeval to the aqueous activity that affected the adjacent plateaus and indicate some hydrological activity occurred after formation of the chasmata although the source of water and sediment remains uncertain the strong correlation between fluvial landforms and light toned layered deposits argues for sustained precipitation surface runoff and fluvial deposition occurring during the hesperian on the plateaus adjacent to valles marineris and along portions of chasmata walls

the reflectance spectra of opal a 0 5 25 μm from the taupo volcanic zone spectra that may identify hydrothermal systems on planetary surfaces 1 opal a the main component of siliceous sinters in many terrestrial hydrothermal systems is a hydrated silicate that commonly incorporates silicified microorganisms the detection of opal a on the surface of mars therefore may carry important implications in the search for extraterrestrial life sinters from the discharge apron of ohaaki pool north island new zealand yielded reflectance spectra wavelengths between 0 5 25 m that indicate the presence of absorbed water trapped water and silanol in opal a two classes 1 and 2 of reflectance spectra were detected between the wavelengths of 6 13 m the class 1 spectrum is similar to existing opal spectra and was collected from well consolidated samples that had low porosity the class 2 spectrum is unique when compared to the spectra of other silica polymorphs and was collected from poorly consolidated samples that had high porosity

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

hirise imaging of impact megabreccia and sub meter aqueous strata in holden crater mars high resolution imaging science experiment hirise images of holden crater mars resolve impact megabreccia unconformably overlain by sediments deposited during two noachian age phases of aqueous activity a lighter toned lower unit exhibiting phyllosilicates was deposited in a long lived quiescent distal alluvial or lacustrine setting an overlying darker toned and often blocky upper unit drapes the sequence and was emplaced during later high magnitude flooding as an impounded uzboi vallis lake overtopped the crater rim the stratigraphy provides the first geologic context for phyllosilicate deposition during persistent wet and perhaps habitable conditions on early mars

young volcanic deposits in the valles marineris mars abstract a study of the interior deposits of the central valles marineris has led to the discovery of a sequence of deposits that cover the chasma floors and range in thickness from that of thin dust to several kilometers the emplacement of the deposits was the last major event in the history of the valles marineris following deposition of older layered interior beds warping faulting erosion and landslide emplacement the young deposits are of three major types 1 dark patches typically occurring along faults 2 light colored deposits locally associated with craters and 3 rugged mottled deposits with in places light colored lobate fronts these young materials may be of volcanic origin as suggested by the low albedo and spectrally gray colors of some their association with faults and possible volcanic craters and calderas and their embayment relations and lobate margins no other mechanism explains all the observed features and relations as well as volcanism if these deposits are volcanic implications are that 1 volcanism was associated with rifting in the valles marineris 2 the volcanism was explosive in places and 3 the volcanism may be as young as the late tharsis volcanism and locally may well be recent

origin and evolution of the layered deposits in the valles marineris mars abstract thick sequences of layered deposits are found in the martian valles marineris they exhibit fine nearly horizontal layering and are present as isolated plateaus of what may have once been more extensive deposits individual sequences of layered deposits are as thick as 5 km the greatest total thicknesses of deposits are found in candor ophir and melas chasmata individual layer thicknesses range from about 70 to 300 m some tilting of sequences is observed but at the best image resolutions no angular unconformities are detectable in the layers the sequences of events in the canyons as deduced from morphologic and stratigraphic evidence was 1 graben formation in response to the tharsis uplift 2 canyon wall retreat and canyon enlargement roughly contemporaneous with formation of the layered deposits 3 deep erosion of the layered deposits 4 landsliding of the canyon walls and 5 eolian erosion of the layered deposits perhaps continuing up to the present we consider four hypotheses for the origin of the layered deposits they are eolian deposits they are remnants of the material that makes up the canyon walls they are deposits of explosive volcanic eruptions or they were deposited in standing bodies of water the rhythmic nature of the layers and their lateral continuity horizontality great thickness and stratigraphic relationships with other units in the canyons all appear most consistent with deposition in an aqueous environment if standing bodies of water existed in the valles marineris they were almost certainly ice covered there are three ways in which sediment could have entered an ice covered lake down through the ice cover up from the lake bottom or in from the lake margins layers of sediment could have been transported downward through an ice cover by foundering or rayleigh taylor instabilities but it is not clear whether there was a viable mechanism for repeatedly accumulating thick sediment layers on top of the ice cover subaqueous volcanic eruption on the lake bottom does not suffer from many of the morphologic arguments that make origin by subaerial volcanism seem improbable while this mechanism is attractive there are no eruptive centers observed and there is no other direct evidence to support it because canyon enlargement took place at roughly the same time as layer deposition debris from the canyon walls is an obvious and likely source for some of the material in the layered deposits however the volume of material removed from the canyon walls may be insufficient to account for all of the presently observed material we conclude that there are several geologically feasible but as yet unproven mechanisms that could have led to formation of thick deposits in ice covered paleolakes in the valles marineris present data are insufficient to choose conclusively among the various possibilities several types of data from the mars observer mission will be useful in further characterizing the deposits and clarifying the process of their origin the deposits should be considered important targets for a future mars sample return mission

compositional stratigraphy of clay bearing layered deposits at mawrth vallis mars phyllosilicates have previously been detected in layered outcrops in and around the martian outflow channel mawrth vallis crism spectra of these outcrops exhibit features diagnostic of kaolinite montmorillonite and fe mg rich smectites along with crystalline ferric oxide minerals such as hematite these minerals occur in distinct stratigraphic horizons implying changing environmental conditions and or a variable sediment source for these layered deposits similar stratigraphic sequences occur on both sides of the outflow channel and on its floor with al clay bearing layers typically overlying fe mg clay bearing layers this pattern combined with layer geometries measured using topographic data from hirise and hrsc suggests that the al clay bearing horizons at mawrth vallis postdate the outflow channel and may represent a later sedimentary or altered pyroclastic deposit that drapes the topography

inverted fluvial features in the aeolis zephyria plana western medusae fossae formation mars evidence for post formation modification 1 the aeolis and zephyria plana contain the western most portion of the medusae fossae formation mff an enigmatic and extensive light toned deposit located in the martian equatorial region and dated from the hesperian to amazonian epochs this area hosts a large population of sinuous ridges srs interpreted as inverted fluvial features formed by precipitation indurated by chemical cementation buried by subsequent deposition and finally exhumed this interpretation of srs as uniformly fluvial represents a modification to an earlier hypothesis for one particular sr of possible glaciofluvial i e esker formation these srs provide a tool to investigate the degree and character of post fluvial modification processes in this region we combined digital terrain models made from context camera ctx and high resolution imaging science experiment hirise stereo image pairs with individual data points from the mars orbiter laser altimeter mola to estimate relief cross sectional profiles longitudinal profiles and slope directions of selected srs longitudinal profiles of several srs display undulations with amplitudes of up to order 100 m while some of the lower amplitude undulations may be due to differential erosion undulations having amplitudes in excess of sr relief require alternative explanations our combined morphologic and topographic analysis suggests that multiple post flow processes including compaction of the deposits and tectonic displacements have modified the original sr profiles specification of the type s and magnitudes of these modification processes will contribute to understanding both the potential of post flow modification of fluvial profiles elsewhere on mars as well as the nature and properties of the mff

layering stratigraphy of eastern coprates and northern capri chasmata mars abstract distinct competent layers are observed in the slopes of eastern coprates chasma part of the valles marineris system on mars our observations indicate that the stratigraphy of coprates chasma consists of alternating thin strong layers and thicker sequences of relatively weak layers the strong competent layers maintain steeper slopes and play a major role in controlling the overall shape and geomorphology of the chasmata slopes the topmost competent layer in this area is well preserved and easy to identify in outcrops on the northern rim of coprates chasma less than 100 m below the southern ophir planum surface the volume of the topmost emplaced layer is at least 70 km 3 and may be greater than 2100 km 3 if the unit underlies most of ophir planum the broad extent of this layer allows us to measure elevation offsets within the north rim of the chasma and in a freestanding massif within coprates chasma where the layer is also observed rim outcrop morphology and elevation differences between ophir and aurorae plana may be indicative of the easternmost extent of the topmost competent layer these observations allow an insight into the depositional processes that formed the stratigraphic stack into which this portion of the valles marineris is carved and they present a picture of some of the last volcanic activity in this area furthermore the elevation offsets within the layer are evidence of significant subsidence of the massif and surrounding material