titan s planetary boundary layer structure at the huygens landing site 1 huygens atmospheric structure instrument hasi for the first time performed an in situ measurement of the thermal structure in titan s atmosphere with a vertical resolution sufficient to analyze the planetary boundary layer pbl the vertical potential temperature profile reveals the presence of a weakly convective pbl with a surface layer thickness of 10 m and an outer layer with a depth of 300 m with a mean eddy diffusivity of only 7 4 10 3 m2 s 1 the turbulence in the pbl is weak the turbulent heat flux in the surface layer was upward but tiny 0 02 w m 2 indicating that the ground surface was marginally warmer than the air the surface heat flux is too small to cause a diurnal variation of the pbl except in the lowest few meters so the observed profile may be a nearly steady state feature within this season at the landing site in the surface layer the mean wind speed is likely to be less than 0 1 m s 1 given the tiny surface heat flux the buoyant production of turbulence is very weak the pbl structure reveals that the weather condition at the time and place of the huygens landing resembles a calm overcast day on earth but is clearly different from the pbl typical for the polar night

influence of crustal heterogeneity on normal fault dimensions and evolution southern south africa extensional system abstract the tectonic configuration of southern south africa is dominated by a continental scale mesozoic extensional system superimposed upon a significant and well constrained palaeozoic lithospheric scale heterogeneity through integrating onshore structural analysis with offshore subsurface studies it is possible to evaluate the applicability of established normal fault growth models in a heterogeneous crustal setting at a basin scale for the first time the 480 km long mesozoic extensional system comprises a number of fault arrays that vary in length from 78 to 230 km coupled with displacements of up to 16 km the fault arrays are amongst the longest and largest displacement of high angle normal faults dips of 45 60 documented in continental lithosphere although comprised of co linear segments rather than the en echelon segment configuration typical of many other extensional systems this atypical geometry is considered to be a consequence of the high degree of structural inheritance between the underlying paleozoic cape fold belt and the subsequent extensional system furthermore it is proposed that the overall displacement length dimensions of the extensional faults were inherited from the underlying compressional faults the establishment of a seismic stratigraphic framework for the pletmos and gamtoos offshore basins reveals that the faults established their long lengths 160 and 90 km respectively within 6 myr of rift initiation prior to accruing their substantial displacement 16 km furthermore there is no evidence for the development of intra basin faults the southern south africa extensional system presents an end member case of structural inheritance where extensional structures are parallel to and reactivate underlying compressional structures in this study structural inheritance is considered to have a significant effect on mechanisms of fault growth the pre existing structures not only result in the rapid establishment of fault lengths of up to 160 km but additionally to strain being localised onto the pre existing fabric to such an extent that no intra basin faults evolve and strain is accommodated entirely on the bounding faults

indian punch rifts tibet the strikes of late cenozoic normal faults in tibet fan systematically from a northwesterly to northeasterly direction from west to east they exhibit an axis of symmetry that bisects the himalayan arc and trends subparallel to india asia motion the two dimensional stress field inferred from the spatial pattern of normal fault orientations can be explained solely by collisional stresses localized along a southern part of the himalayan arc continued insertion of indian crust into tibet can explain the persistence of extension and may be increasing plateau crustal thickness and elevation coeval with rifting

a magnetotelluric study of the damara belt in namibia 2 mt phases over 90 reveal the internal structure of the waterberg fault omaruru lineament abstract magnetotelluric mt observations at some sites in the vicinity of the waterberg fault omaruru lineament wf ol a major tectono stratigraphic zone boundary in the central zone of the damara belt show evidence for strong three dimensional 3d effects we observe very high skew values phases over 90 and a strong correlation of parallel components of the electric and magnetic fields at long periods because of the dense site spacing and good spatial coverage we can positively attribute these effects to local geology and are able to resolve structural detail within the wf ol mapping latorraca s electric characteristic vectors in form of ellipses proved particularly useful in identifying key elements of the conductivity structure for subsequent modelling 3d and 2d anisotropic modelling can reproduce most of the observed 3d effects the conductivity anomalies revealed in the area are i a conductive ring structure in the shallow crust along the northern part of the profile ii an anisotropic region in the upper crust with high conductivity parallel to the wf ol iii anisotropy in the lower crust with a different but undetermined strike direction and iv a shallow elongated conductor sub normal to the wf ol modelling studies further suggest that the anisotropic fault zone is approximately 10 km wide and may reach down to a depth of 14 km or more

a soft solid surface on titan as revealed by the huygens surface science package the surface of saturn s largest satellite titan is largely obscured by an optically thick atmospheric haze and so its nature has been the subject of considerable speculation and discussion1 the huygens probe entered titan s atmosphere on 14 january 2005 and descended to the surface using a parachute system2 here we report measurements made just above and on the surface of titan by the huygens surface science package3 4 acoustic sounding over the last 90 m above the surface reveals a relatively smooth but not completely flat surface surrounding the landing site penetrometry and accelerometry measurements during the probe impact event reveal that the surface was neither hard like solid ice nor very compressible like a blanket of fluffy aerosol rather the huygens probe landed on a relatively soft solid surface whose properties are analogous to wet clay lightly packed snow and wet or dry sand the probe settled gradually by a few millimetres after landing

transient surface liquid in titan s polar regions from cassini cassini radar images of titan s south polar region acquired during southern summer contain lake features which disappear between observations these features show a tenfold increases in backscatter cross section between images acquired one year apart which is inconsistent with common scattering models without invoking temporal variability the morphologic boundaries are transient further supporting changes in lake level these observations are consistent with the exposure of diffusely scattering lakebeds that were previously hidden by an attenuating liquid medium we use a two layer model to explain backscatter variations and estimate a drop in liquid depth of approximately 1 m per year on larger scales we observe shoreline recession between iss and radar images of ontario lacus the largest lake in titan s south polar region the recession occurring between june 2005 and july 2009 is inversely proportional to slopes estimated from altimetric profiles and the exponential decay of near shore backscatter consistent with a uniform reduction of 4 1 3 m in lake depth of the potential explanations for observed surface changes we favor evaporation and infiltration the disappearance of dark features and the recession of ontario s shoreline represents volatile transport in an active methane based hydrologic cycle observed loss rates are compared and shown to be consistent with available global circulation models to date no unambiguous changes in lake level have been observed between repeat images in the north polar region although further investigation is warranted these observations constrain volatile flux rates in titan s hydrologic system and demonstrate that the surface plays an active role in its evolution constraining these seasonal changes represents the first step toward our understanding of longer climate cycles that may determine liquid distribution on titan over orbital time periods

making ends meet in gondwana retracing the transforms of the indian ocean and reconnecting continental shear zones interpretation of the detailed patterns of ocean floor transforms revealed by satellite altimetry enables the creation of the indian ocean to be described quantitatively as four consecutive plate tectonic regimes separated at 200 136 89 and 43 ma each regime is reversed in turn by keeping transform termini coincident and colinear until conjugate points on the margins of pre existing plates regain their pre regime integrity progressive elimination of the indian ocean demonstrable as a smooth computer animation http www kartoweb itc nl gondwana leads to a refined re assembly of the continental fragments of central gondwana that is substantiated by new geological data a sequence of euler interval poles that describes the dispersal of the gondwana fragments time calibrated against available magnetic anomaly data is given the model requires a mid cretaceous position for india s southern tip about 1000 km south of madagascar prior to india s rapid northward migration

cassini radar views the surface of titan the cassini titan radar mapper imaged about 1 of titan s surface at a resolution of 0 5 kilometer and larger areas of the globe in lower resolution modes the images reveal a complex surface with areas of low relief and a variety of geologic features suggestive of dome like volcanic constructs flows and sinuous channels the surface appears to be young with few impact craters scattering and dielectric properties are consistent with porous ice or organics dark patches in the radar images show high brightness temperatures and high emissivity and are consistent with frozen hydrocarbons

physical properties of titan s surface at the huygens landing site from the surface science package acoustic properties sensor api s abstract we present the results from the first sonar to be deployed outside of earth and the first active acoustic instrument on titan onboard the huygens probe and the implications of its data for the geomorphology and characteristics of the huygens landing site signals were recorded from 90 m downwards until impact with a maximum sensor footprint diameter at the ground of 39 2 m probe impact speed was measured to be 4 67 m s 1 derivation of terrain topography in a transect beneath the probe may indicate a ridge trough terrain with an amplitude of about 1 m and a wavelength of about 10 m although a flat surface is also consistent with the results modelling of the returned signal indicates that the surface acoustic properties at the landing site must be specular in nature which may have two possible not incompatible causes the surface may consist of sorted interlocking grains smooth on the centimetre scale which would imply either fluvial sorting or the infill of small particles interstitial to the larger particles similar to a terrestrial playa alternatively specularity may indicate the presence of methane as an interstitial liquid or as very small pools due to mission constraints tens of metres around the landing site were not well imaged by huygens cameras except for the narrow azimuth observed after impact the camera did not look straight down and was not in imaging mode during the last few hundred metres of descent thus the data presented are among the few direct observations of the landing site surroundings

hydrocarbon lakes on titan distribution and interaction with a porous regolith from 10 to more than 100 000 km 2 the size and location of lakes provide constraints on parameters associated with subsurface transport using porous media properties inferred from huygens probe observations timescales for flow into and out of observed lakes are shown to be in the tens of years similar to seasonal cycles derived timescales are compared to the time between collocated sar observations in order to considertheroleofsubsurfacetransportintitan shydrologic cycle citation hayes a et al 2008 hydrocarbon lakes on titan distribution and interaction with a porous regolith geophys res lett 35 l09204 doi 10 1029 2008gl033409

plumbing the depths of ligeia considerations for depth sounding in titan s hydrocarbon seas saturn s moon titan is the only satellite in this solar system with a dense atmosphere and hydrocarbon seas the titan mare explorer time mission would splashdown a capsule to float for 3 months on ligeia mare a several hundred kilometer wide sea near titan s north pole among time s scientific goals is the determination of the depth of ligeia to be achieved with an acoustic depth sounder since titan s surface temperature is known to vary around 92 k all instruments must be ruggedized to operate at cryogenic temperatures this paper s contributions include an approach to infer key acoustic properties of this remote environment and the extraterrestrial environment s influence on the development of a cryogenic depth sounder additionally an approach is formulated to infer the transducer s response sensitivity and performance when in situ calibration is impossible or when replicating key environmental conditions is too costly

crustal structure of the southern margin of the african continent results from geophysical experiments 1 a number of geophysical onshore and offshore experiments were carried out along a profile across the southern margin of the african plate in the framework of the inkaba yeafrica project refraction seismic experiments show that moho depth decreases rapidly from over 40 km inland to around 30 km at the present coast before gently thinning out toward the agulhas falkland fracture zone which marks the transition zone between the continental and oceanic crust in the region of the abruptly decreasing moho depth in the vicinity of the boundary between the namaqua natal mobile belt and the cape fold belt lower crustal p wave velocities up to 7 4 km s are observed this is interpreted as metabasic lithologies of precambrian age in the namaqua natal mobile belt or mafic intrusions added to the base of the crust by younger magmatism the velocity model for the upper crust has excellent resolution and is consistent with the known geological record a joint interpretation of the velocity model with an electrical conductivity model obtained from magnetotelluric studies makes it possible to correlate a high velocity anomaly north of the center of the beattie magnetic anomaly with a highly resistive body

penetrometry of granular and moist planetary surface materials application to the huygens landing site on titan the huygens probe landed on the then unknown surface of titan in january 2005 a small protruding penetrometer part of the surface science package ssp was pushed into the surface material measuring the mechanical resistance of the ground as the probe impacted the landing site we present laboratory penetrometry into room temperature surface analogue materials using a replica penetrometer to investigate further the nature of titan s surface and examine the sensor s capabilities the results are then compared to the flight instrument s signature and suggest the titan surface substrate material consists of sand sized particles with a mean grain size 2 mm a possible thin 7 mm coating with mechanical properties similar to terrestrial snow may overlie this substrate although due to the limited data we are unable to detect any further layering or grading within the near surface material the unusual weakening with depth of the signature returned from titan has to date only been reproduced using a damp sand target that becomes progressively wetter with depth and supports the suggestion that the surface may consist of a damp and cohesive material with interstitial liquid contained between its grains comparison with terrestrial analogues highlights the unusual nature of the landing site material

towards defining a baseline status of scarce groundwater resources in anticipation of hydraulic fracturing in the eastern cape karoo south africa salinity aquifer yields and groundwater levels

fluvial erosion and post erosional processes on titan the surface of titan has been revealed by cassini observations in the infrared and radar wavelength ranges as well as locally by the huygens lander instruments sand seas recently discovered lakes distinct landscapes and dendritic erosion patterns indicate dynamic surface processes this study focus on erosional and depositional features that can be used to constrain the amount of liquids involved in the erosional process as well as on the compositional characteristics of depositional areas fluvial erosion channels on titan as identified at the huygens landing site and in radar and visible and infrared mapping spectrometer vims observations have been compared to analogous channel widths on earth yielding average discharges of up to 1600 m3 s for short recurrence intervals that are sufficient to move centimeter sized sediment and significantly higher discharges for long intervals with respect to the associated drainage areas this roughly translates to 1 150 cm day runoff production rates with 10 years recurrence intervals and by assuming precipitation this implies 0 6 60 mm h rainfall rates thus the observed surface erosion fits with the methane convective storm models as well as with the rates needed to transport sediment during cassini s t20 fly by the vims observed an extremely eroded area at 30 w 7 s with resolutions of up to 500 m pixel that extends over thousands of square kilometers the spectral characteristics of this area change systematically reflecting continuous compositional and or particle size variations indicative of transported sediment settling out while flow capacities cease to account for the estimated runoff production and widespread alluvial deposits of fine grained material release of area dependent large fluid volumes are required only frequent storms with heavy rainfall or cryovolcanic induced melting can explain these erosional features

dissipation of titan s south polar clouds nearly all adaptive optics images of titan taken between december 2001 and november 2004 showed tropospheric clouds located within 30 of the south pole we report here on a dissipation of titan s south polar clouds observed in twenty nine keck and gemini images taken between december 2004 and april 2005 the near complete lack of south polar cloud activity during this time and subsequent resurgence months later at generally higher latitudes may be the beginning of seasonal change in titan s weather the 5 month decrease in cloud activity may also have been caused by methane rainout from a large cloud event in october 2004 understanding the seasonal evolution of titan s clouds and of any precipitation associated with them is essential for interpreting the geological observations of fluid flow features observed over a wide range of titan latitudes with the cassini huygens spacecraft

magnetotelluric image linked to surface geology across the cape fold belt south africa terra nova 24 207 212 2012 abstract the subsurface structure of the cape fold belt cfb that traverses southern africa remains largely unknown because it lacks deep penetrating high resolution geophysics this hampers studies from local scale exploration for important resources such as water to continental scale modelling such as gondwana reconstructions our magnetotelluric mt soundings across the cfb provide a high resolution crustal scale electrical conductivity image inversion models of these data correlate well with surface geology and resolve deep resistive roots of the cfb s regional palaeozoic quartzite ridges swartberg and outeniqua mountains and thin tectonic wedges of proterozoic rocks of higher resistivity kango and kaaimans inliers separated by 2 3 km of cretaceous sediments in asymmetric intermontaine basins one of these basins the oudtshoorn basin is flanked by a listric normal fault rooted in an upper crustal detachment zone and is underlain by a massive conductivity anomaly that is likely to be a major saline water reservoir

surface albedo spectral properties of geologically interesting areas on titan we investigate the nature and possible formation processes of three areas on titan s surface which have been suggested as geologically interesting hotei regio tui regio and sotra patera we also reanalyze the spectral characteristics of the huygens landing site we apply a statistical principal component analysis pca and a radiative transfer rt method on the visual and infrared mapping spectrometer datacubes in order to retrieve the surface albedo of distinct spectral units in the near infrared we have been able to exploit only a subset of the currently available hotei regio data which are in general not optimal in terms of geometry for an analysis with a plane parallel rt code our inferred surface albedos present generally higher values from 1 to 2 m and lower ones at 0 94 and in the 2 6 5 m region the regions of interest rois within hotei regio tui regio and sotra patera are always significantly brighter than the surrounding areas the largest variations are found longward of 2 m and mainly at 5 m this higher surface albedo with respect to the surrounding area and in general the fact that the spectral behavior is different for each of these areas is probably indicative of diverse chemical compositions and origins we compare the spectral albedos with some suggested surface candidates on titan such as h2o co2 and ch4 ices as well as tholin and discuss possible chemical composition variations as well as other interpretations

sonar equations for planetary exploration the set of formulations commonly known as the sonar equations have for many decades been used to quantify the performance of sonar systems in terms of their ability to detect and localize objects submerged in seawater the efficacy of the sonar equations with individual terms evaluated in decibels is well established in earth s oceans the sonar equations have been used in the past for missions to other planets and moons in the solar system for which they are shown to be less suitable while it would be preferable to undertake high fidelity acoustical calculations to support planning execution and interpretation of acoustic data from planetary probes to avoid possible errors for planned missions to such extraterrestrial bodies in future doing so requires awareness of the pitfalls pointed out in this paper there is a need to reexamine the assumptions practices and calibrations that work well for earth to ensure that the sonar equations can be accurately applied in combination with the decibel to extraterrestrial scenarios examples are given for icy oceans such as exist on europa and ganymede titan s hydrocarbon lakes and for the gaseous atmospheres of for example jupiter and venus

mapping of titan results from the first titan radar passes the first two swaths collected by cassini s titan radar mapper were obtained in october of 2004 ta and february of 2005 t3 the ta swath provides evidence for cryovolcanic processes the possible occurrence of fluvial channels and lakes and some tectonic activity the t3 swath has extensive areas of dunes and two large impact craters we interpret the brightness variations in much of the swaths to result from roughness variations caused by fracturing and erosion of titan s icy surface with additional contributions from a combination of volume scattering and compositional variations despite the small amount of titan mapped to date the significant differences between the terrains of the two swaths suggest that titan is geologically complex the overall scarcity of impact craters provides evidence that the surface imaged to date is relatively young with resurfacing by cryovolcanism fluvial erosion aeolian erosion and likely atmospheric deposition of materials future radar swaths will help to further define the nature of and extent to which internal and external processes have shaped titan s surface

velocity conductivity relationships for mantle mineral assemblages in archean cratonic lithosphere based on a review of laboratory data and hashin shtrikman extremal bounds article i nfo can mineral physics and mixing theories explain field observations of seismic velocity and electrical conductivity and is there an advantage to combining seismological and electromagnetic techniques these two questions are at the heart of this paper using phenomenologically derived state equations for individual minerals coupled with multi phase hashin shtrikman extremal bound theory we derive the likely shear and compressional velocities and electrical conductivity at three depths 100 km 150 km and 200 km beneath the central part of the slave craton and beneath the kimberley region of the kaapvaal craton based on known petrologically observed mineral abundances and magnesium numbers combined with estimates of temperatures and pressures we demonstrate that there are measurable differences between the physical properties of the two lithospheres for the upper depths primarily due to the different ambient temperature but that differences in velocity are negligibly small at 200 km we also show that there is an advantage to combining seismic and electromagnetic data given that conductivity is exponentially dependent on temperature whereas the shear and bulk moduli have only a linear dependence in cratonic lithospheric rocks focussing on a known discontinuity between harzburgite dominated and lherzolitic mantle in the slave craton at a

fluvial erosion as a mechanism for crater modification on titan abstract there are few identifiable impact craters on titan especially in the polar regions one explanation for this observation is that the craters are being destroyed through fluvial processes such as weathering mass wasting fluvial incision and deposition in this work we use a landscape evolution model to determine whether or not this is a viable mechanism for crater destruction on titan we find that fluvial degradation can modify craters to the point where they would be unrecognizable by an orbiting spacecraft such as cassini given enough time and a large enough erosion rate a difference in the erosion rate between the equator and the poles of a factor of a few could explain the latitudinal variation in titan s crater population fluvial erosion also removes central peaks and fills in central pits possibly explaining their infrequent occurrence in titan craters although many craters on titan appear to be modified by aeolian infilling fluvial modification is necessary to explain the observed impact crater morphologies thus it is an important secondary modification process even in titan s drier equatorial regions