Olivine or Impact Melt: Nature of the "Orange" Material on Vesta from Dawn

NASA's Dawn mission observed a great variety of colored terrains on asteroid (4) Vesta during its survey with the Framing Camera (FC). Here we present a detailed study of the orange material on Vesta, which was first observed in color ratio images obtained by the FC and presents a red spectral slope. The orange material deposits can be classified into three types, a) diffuse ejecta deposited by recent medium-size impact craters (such as Oppia), b) lobate patches with well-defined edges, and c) ejecta rays from fresh-looking impact craters. The location of the orange diffuse ejecta from Oppia corresponds to the olivine spot nicknamed "Leslie feature" first identified by Gaffey (1997) from ground-based spectral observations. The distribution of the orange material in the FC mosaic is concentrated on the equatorial region and almost exclusively outside the Rheasilvia basin. Our in-depth analysis of the composition of this material uses complementary observations from FC, the visible and infrared spectrometer (VIR), and the Gamma Ray and Neutron Detector (GRaND). Combining the interpretations from the topography, geomorphology, color and spectral parameters, and elemental abundances, the most probable analog for the orange material on Vesta is impact melt

Decisin support system for risk assessment and management of floods

The objective of the RAMFLOOD project is to develop and validate a new decision support system (DSS) for the risk assessment and management of emergency scenarios due to severe floods. The DSS combines environmental and geo-physical data from earth observation, with advanced computer simulation and graphical visualisation methods and artificial intelligence techniques, for generating knowledge contributing to the risk prevention of floods and the design of effective response actions maximising the safety of infrastructures and human life

The geophysical evolution of impact basins and volcanic structures on Mercury and the Moon

The geologic histories of most terrestrial bodies are dominated by two major processes: meteorite bombardment and volcanism. The forms that the resulting impact craters and volcanic structures take can tell us a great deal about the ways in which these processes occur and about the environment of the host body at the time of their formation. The surfaces of bodies like Mercury and the Moon are old, however, and most such features formed more than a billion years in the past. Impact craters and volcanic structures are thus generally not visible in their original states, but instead in a form which has evolved over geologic time. ^ In this work, I combine observations of planetary surfaces from spacecraft like MESSENGER and GRAIL with modern numerical modeling techniques in order to explore the various ways in which the long-term geophysical evolution of impact craters and volcanic structures can reveal information about the subsurface environment. I find that the pattern of fractures on the floors of the Rachmaninoff, Raditladi, and Mozart peak-ring impact basins on Mercury reveals the contours of the underlying terrain; that the present-day gravitational and topographic signatures over Orientale Basin emerged due to a combination of syn- and post-impact processes which can help to constrain both the parameters of the impact and the rheology of the lunar mantle; and that the tremendous sizes at which lunar lava tubes can be stable open up both new ways of interpreting GRAIL observations of the lunar gravity field and new possibilities for human exploration of the Moon

The Pitted Impact Deposits on Asteroid 4 Vesta: An In-Depth Analysis

This work analyzes geomorphological devolatilization features on the atmosphereless asteroid Vesta. In particular, it predominantly analyzes the features associated with the crater Marcia, as those add up to more than 96% on the whole body and are the only ones occurring within the ejecta of a crater. These features are called Pitted Impact Deposits, or short PIDs, and they have been previously identified on Mars, Vesta and the dwarf planet Ceres. PIDs are characterized by closely spaced pits that occur as locally confined clusters of several kilometers length. The individual pits can overlap and often share boundaries. They lack raised rims as would be typical of an impact crater and are polygonal to circular in shape. Furthermore, they show distinct spectral characteristics like higher reflectance at 750 nm and more intense pyroxene absorptions near 0.9 and 1.9 µm. It is evident through previous studies that PIDs formed via degassing or devolatilization of parts of the ejecta, yet the detailed mechanism behind remained debated. Additionally to the previously known dominance of pyroxene-rich HED-like material on Vesta (HED: howardite, eucrite, diogenite meteorites), many studies have reported on the existence of OH-bearing material and the so-called ‘dark material’ which has been proposed to originate from influx of carbonaceous chondrite material. The identified OH is likely bound within the crystal structure of phyllosilicates (that are commonly found in carbonaceous chondrites) and is able to leave the crystal structure when heated. All remote observations shown here were obtained by NASA’s Dawn mission. The presented analysis show that the formation of PIDs is controlled by the proportion of an ejecta deposit’s volume to surface area, or depth. Many PIDs are located in small craters or at steep topographic slopes that existed prior to the Marcia impact or to the time of PID formation. This enables the estimation of the pre-existing topography and therefore of the shape and extent of the post-impact ejecta deposit. The accumulation of ejecta at these sites leads to a slower cooling of the ejecta deposit, a larger volume not exposed to the space environment and an extended possibility for volatiles to escape from its host mineral. The depth of the ejecta deposit appears to control the shape and extent of the developing devolatilization vents and therefore, of the individual pits themselves. The proportion of volatiles within the whole ejecta is estimated here to be less than 2 wt% and the proportion of lost volatiles at the PIDs’ sites to ~1 wt%. This shows that particularly elevated volatile contents are not needed to form PIDs. PIDs are always part of a larger impact deposit not featuring a pitted surface. This suggest that the original material of both deposit parts were identical or very similar. The spectral changes of the PIDs with respect to their immediate surroundings are not consistent with variations in grain size, roughness or glass content. One possibility of creating similar spectral characteristics is the removal of darkening agents. At high temperatures, organic material (which are commonly dark) can decompose, as do other components of carbonaceous chondrites. Tochilinite for example is a major constituent in the carbonaceous chondrite Murchison and decomposes already at 400 °C. However, the mere removal of dark components cannot explain all aspects of spectral characteristics shown for PIDs, i.e. the ratio of pyroxene band strength to reflectance at 750 nm with respect to other more typical regions on Vesta. This thesis furthermore presents laboratory experiments in order to explain the PIDs’ spectral characteristics. Both terrestrial and meteoritic materials were used. These were assembled to adequately represent the Vestan regolith. The experiments involving the heating of these analog materials show that hematite formed due to oxidation and therefore, a strong reddening of the visible spectral slope of the samples was observed. This is not observed on Vesta, yet might be explained. First, the ejecta deposit on Vesta is likely very heterogeneous, as has been shown by previous studies. This can lead to a smaller and slower extent of these oxidation processes. Second, the estimated devolatilization duration is in the range of hours to days, possibly inhibiting the onset of hematite formation or the incapability of remote spectrometers to record the small amounts that might have already formed. Third, the processes of space weathering of hematite over geological timescales are not well-known, which could additionally play a role. In combination with existing literature, the laboratory experiments presented here show that an oxidizing environment together with higher temperatures (≥400 °C, well below the minerals’ melting point) can result in similar spectral characteristics, i.e. higher reflectance and pyroxene band strength, as shown for PIDs. The underlying process could involve the migration of Fe2+ to the grain surfaces, where it increases the relative iron abundance that electromagnetic energy (i.e., light) encounters first which in turn intensifies the pyroxene absorption. Many studies have observed similar processes where Fe2+ is converted to Fe3+ and forms hematite (Fe2O3) or other iron (hydr-)oxides. An alternative explanation also includes the migration of Fe2+, yet to its preferred crystallographic M2 site, where it likewise would intensify the pyroxene absorption. Original pyroxene crystals might have been disordered regarding their cation distribution, whereas the temperature increase would enable the cations to migrate to their preferred position. This work shows that oxidation processes can occur on planetary bodies thought to be dry. The surficial contamination with carbonaceous chondrite material enables this process, which might be relevant to future space missions and could influence the search for organic matter.Diese Arbeit analysiert geomorphologische Entgasungserscheinungen auf dem atmosphärenlosen Asteroiden Vesta, insbesondere jene, die mit dem Krater Marcia assoziiert sind. Diese machen über 96% der Gesamtanzahl aus und sind die einzigen, die in der Ejekta eines Kraters auftreten. Diese Pitted Impact Deposits (PIDs, zu deutsch: Einschlagsablagerungen, die eng gruppierte Senken/Mulden aufweisen) wurden zuvor bereits auf Vesta, sowie schon auf dem Mars und auf dem Zwergplaneten Ceres beobachtet. Die eng gruppierten Senken treten als Ansammlung von mehreren Kilometern Länge auf, können überlappen und teilen sich häufig ihre Ränder. Lokal sind sie stark begrenzt zu ihrem direkten Umfeld, welches ebenfalls aus Einschlagsablagerungen besteht. Sie zeigen zudem keine erhöhten Ränder, was für Einschlagskrater typisch wäre. Diese Senken sind polygonal bis rund geformt und zeigen zudem spektrale Besonderheiten, wie höhere Reflektanz bei 750 nm und intensivere Pyroxen-Absorptionsbanden bei ~0.9 und 1.9 µm, auf. Während eindeutig ist, dass diese Erscheinungsformen durch Entgasung bzw. Devolatilisierung der Ejekta entstehen, blieb die genaue Entstehungsursache auf Vesta bisher jedoch ungeklärt. Viele Studien haben zusätzlich zum bereits bekannten und vorherrschenden, pyroxenreichen HED-ähnlichen Material (von den pyroxenreichen HED-Meteoriten: Howardite, Eukrite, Diogenite) OH-haltiges Material und ‘dunkles Material’, wahrscheinlich von kohligen Chondriten stammend, im Regolith von Vesta nachgewiesen bzw. eindeutige Hinweise darauf gefunden. Dieses OH liegt in den Kristallstrukturen von Phyllosilikaten vor und kann unter Temperatureinwirkung aus der Kristallstruktur gelöst werden und entgasen bzw. devolatilisieren. Alle hier dargestellten Beobachtungen des Asteroiden Vesta stützen sich auf Daten, die von der NASA-Raumsonde Dawn aufgenommen wurden. Die hier vorgestellten Analysen zeigen, dass die Entgasung mit Senkenbildung vornehmlich durch das Verhältnis von Volumen zur Oberfläche bzw. Tiefe der Ablagerung kontrolliert wird, da viele PIDs in bereits vor dem Impakt existierenden Kratern und an steilen topografischen Erhöhungen auftreten. Das Vorkommen an solch topographisch eindeutigen Morphologien ermöglicht die Abschätzung der Topographie vor dem Marcia-bildenden Impakt sowie die Abschätzung der Ausprägung und Form der Einschlagsablagerungen nach Impakt. Die Akkumulation von Ejekta an diesen topographisch markanten Stellen führt zu einer verlangsamten Abkühlung des Ejektamaterials, einem größeren erhitzten Volumen welches nicht an der Oberfläche der Weltraumumgebung ausgesetzt wird und dabei zu einer verlängerten Möglichkeit, Volatile aus Mineralstrukturen zu lösen. Die Tiefe der Ablagerung bedingt die Ausprägung der entstehenden Entgasungsschlote und damit der Senken. Der Anteil an Volatilen in der Gesamtejekta wird mit 2% geschätzt und der Anteil bei Ausgasung der PIDs mit 1%. Dies zeigt, dass besonders hohe Volatilanteile nicht benötigt werden, um diese Erscheingsformen hervorzurufen. PIDs sind immer Teil einer größer ausgeprägten Einschlagsablagerung, was ein identisches Ausgangsmaterial suggeriert. Die spektralen Veränderungen von PIDs im Vergleich zu ihrer direkten Umgebung sind nicht konsistent mit Veränderungen von Korngrößen, Rauigkeit oder dem Vorhandensein von Glaskomponenten im Material. Eine Möglichkeit, die gezeigten spektralen Eigenschaften zu erzeugen, ist das Entfernen von ‘dunklem Material’. Bei erhöhten Temperaturen können organische Strukturen (die meist dunkel sind) sowie andere Komponenten von kohligen Chondriten zerfallen. Tochilinit zum Beispiel, ein Hauptbestandteil der Matrix im kohligen Chondrit Murchison, zerfällt bereits bei 400 °C. Jedoch kann die bloße Entfernung von ‘dunklem Material’ nicht alle Aspekte der spektralen Eigenschaften der PIDs erklären, wie z.B. das höhere Verhältnis der Stärke der Pyroxenabsorption im Vergleich zur Reflektanz bei 750 nm im Vergleich zu anderen typischen Regionen auf Vesta. Diese Arbeit präsentiert darüber hinaus Laborexperimente, die die spektralen Eigenschaften der PIDs erklären sollten. Diese wurden mit terrestrischem und meteoritischem Material, welches sich zur Simulation des Regoliths auf Vesta sehr gut eignet, durchgeführt. Die Temperaturexperimente zeigen die Entstehung von Hämatit durch Oxidation und damit einhergehend eine sehr starke Steigung der Reflektanz im visuellen Wellenlängenbereich. Dies wird nicht auf Vesta beobachtet, was jedoch auch andere Gründe haben kann. Zum einen ist das Material auf Vesta sehr inhomogen gemischt, was zu verlangsamten Reaktionen führen kann. Außerdem liegt die geschätzte Ausgasungszeit der PIDs auf Vesta bei Stunden oder wenigen Tagen, was unter Umständen dazu führt, dass die Bildung von Hämatit noch nicht begonnen hat oder nur in einem so geringen Maß, welches nicht per Spektroskopie erkannt werden kann. Des Weiteren ist wenig über die Verwitterung von Hämatit, welches der Weltraumumgebung über geologische Zeiträume ausgesetzt wurde, bekannt, was ebenso eine Rolle spielen könnte. Vor allem jedoch zeigen die Laborexperimente, in Verbindung mit bereits existierender Literatur zu dem Thema, dass eine oxidierende Umgebung in Verbindung mit erhöhten Temperaturen (≥400 °C, weit unter dem Schmelzpunkt der Minerale) genau jene Erscheinung der PIDs - erhöhte Reflektanzen und intensivere Pyroxen-Absorptionsbanden - hervorrufen kann. Dabei könnten Fe2+-Kationen aus ihrer Kristallposition mobilisiert werden und zu den Partikelrändern migrieren. In vielen Studien, auch mit extraterrestrischem Material, wurde dies bereits beobachtet; mit dem Resultat, dass Fe2+ zu Fe3+ oxidiert und nach Verlassen der Pyroxenstruktur in Verbindung mit den verfügbaren Volatilen Hämatit (Fe2O3) oder andere Eisen(hydr-)oxide bildet. Eine mögliche Anreicherung von Fe2+-Kationen während dieses Prozesses an den Partikelrändern führt dazu, dass eletromagnetische Energie (Licht) zunächst auf mehr Eisen-Kationen im Kristallgitter trifft, was eine Intensivierung der Absorptionsbanden nach sich zieht. Alternativ kann es sein, dass sich im ursprünglich ungeordneten Kristall durch die Erhöhung der Temperatur die Kationen neu ordnen können und Fe2+ in seine bevorzugte kristallographische M2-Position migriert. Auch dies würde eine Intensivierung der Pyroxen-Absorptionsbanden hervorrufen. Diese Arbeit zeigt, dass Oxidationsprozesse auch auf Körpern geschehen können, die eigentlich als "trocken" gelten. Die oberflächliche Kontamination mit kohligen Chondriten ermöglicht dabei diesen Prozess, was für zukünftige Missionen und die Suche nach organischem Material eine Rolle spielen könnte

Mars: Past, Present, and Future. Results from the MSATT Program, part 1

This volume contains papers that were accepted for presentation at the workshop on Mars: Past, Present, and Future -- Results from the MSATT Program. Topics include, but are not limited to: Martian impact craters; thermal emission measurements of Hawaiian palagonitic soils with implications for Mars; thermal studies of the Martian surface; Martian atmospheric composition studies; temporal and spatial mapping of Mars' atmospheric dust opacity and surface albedo; studies of atmospheric dust from Viking IR thermal mapper data; the distribution of Martian ground ice at other epochs; numerical simulation of thermally induced near-surface flows over Martian terrain; the pH of Mars; the mineralogic evolution of the Martian surface through time; geologic controls of erosion and sedimentation on Mars; and dielectric properties of Mars' surface: proposed measurement on a Mars Lander

The use of Terrestrial Laser Scanning in characterizing active tectonic processes from postseismic slip to the long term growth of normal faults

This thesis investigates two main hypotheses regarding uncertainty in the measurement of paleoseismic offsets used to estimate fault activity and paleoearthquake magnitudes on normal faults: (1) That variations in fault geometry have a significant effect on throw-rates and fault offsets; and (2) that postseismic deformation can be a significant component of the total fault slip for moderate magnitude earthquakes. These hypotheses are tested using high resolution terrestrial laser scan datasets of normal fault topographic offsets and surface ruptures. The first hypothesis is addressed by studying the crustal scale Campo Felice active normal fault in the Central Apennines, Italy. Variation in throw-rate along strike since the last glacial maximum (15 ka ±3) is measured from an offset periglacial surface at two hundred and fifty sites using cross sectional data derived from a high resolution terrestrial laser scan (TLS) dataset. The measurements are used to create a detailed throw-rate profile. Field measurements of fault geometry (strike, dip and kinematic slip direction) are also gathered. Variation in fault throw-rate is found to correlate with fault strike. A study of weathered band thickness on the exposed Miocene limestone bedrock fault scarp, thought to have been created by single past slip events on the fault also appears to correlate with fault strike. A strain-rate profile is calculated using the throw-rate profile and the field measurements of kinematic slip. In contrast to throw-rate, strainrate is independant of changes in fault strike and dip. It is suggested that strain-rate in comparison to throw-rate provides a more robust measure of fault activity as it is unaffected by changes in fault geometry. The outcome of this study is that paleoseismic studies on active faults should take into account fault geometry before choosing sites which may have anomalously high or low paleoseismic offsets. Fault geometry introduces significant uncertainty into the estimation of inferred paleoearthquake magnitudes from paleoseismic offsets and hence seismic hazard analysis. The second hypothesis is addressed through the study of near-field postseismic deformation (surface rupture afterslip) following the 6th April 2009 6.3 Mw L’Aquila earthquake, created by slip on the Paganica normal fault in the Central Italian Apennines. A novel use of TLS technology allowed the postseismic deformation at four sites along the L’Aquila surface rupture to be measured between 8 – 126 days after the earthquake. Complimentary measurements of postseismic deformation at a fifth site using a robotic total station were combined with the TLS datasets to describe the along strike variation in postseismic deformation. The near-field postseismic deformation measured occurred mostly in the immediate hangingwall of the surface rupture and increased with decreasing rate over time. The postseismic deformation measured is comparable to theoretical and empirical models which have been used to describe afterslip for previous earthquakes. The magnitude of near-field postseismic deformation was up to 60% that of the coseismic offset in the near-field and suggests that postseismic deformation can form a significant component of paleoseismic offsets of moderate magnitude. Postseismic deformation was also found to be greatest above regions of the fault zone where a high coseismic slip gradient existed, suggesting that postseismic deformation occurs at the periphery of the coseismic slip patch within the fault zone. Regression relationships which relate surface offset to moment magnitude are populated by field observations of surface offsets where earthquake magnitude is known. These regression relationships are then used to infer paleoearthquake magnitudes from paleoseismic offsets. The field studies used to populate regression relationships do not routinely take into account the potential effects of fault geometry and significant postseismic slip. As a result paleoearthquake magnitudes inferred from such regression relationships are maybe over estimated. It is suggested that future regression relationships of surface offset and moment magnitude should factor in the effects of fault geometry and postseismic deformation in order to produce a relationship in which surface offset (both coseismic and postseismic) is described for a range of magnitudes and, where possible, any local effects of fault geometry are removed from the input dataset. The production of such a relationship will allow paleoseismologists to measure combined coseismic and postseismic offsets from field studies and to infer paleoearthquake magnitude with decreased uncertainty

Camera positioning for 3D panoramic image rendering

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University London.Virtual camera realisation and the proposition of trapezoidal camera architecture are the two broad contributions of this thesis. Firstly, multiple camera and their arrangement constitute a critical component which affect the integrity of visual content acquisition for multi-view video. Currently, linear, convergence, and divergence arrays are the prominent camera topologies adopted. However, the large number of cameras required and their synchronisation are two of prominent challenges usually encountered. The use of virtual cameras can significantly reduce the number of physical cameras used with respect to any of the known camera structures, hence adequately reducing some of the other implementation issues. This thesis explores to use image-based rendering with and without geometry in the implementations leading to the realisation of virtual cameras. The virtual camera implementation was carried out from the perspective of depth map (geometry) and use of multiple image samples (no geometry). Prior to the virtual camera realisation, the generation of depth map was investigated using region match measures widely known for solving image point correspondence problem. The constructed depth maps have been compare with the ones generated using the dynamic programming approach. In both the geometry and no geometry approaches, the virtual cameras lead to the rendering of views from a textured depth map, construction of 3D panoramic image of a scene by stitching multiple image samples and performing superposition on them, and computation of virtual scene from a stereo pair of panoramic images. The quality of these rendered images were assessed through the use of either objective or subjective analysis in Imatest software. Further more, metric reconstruction of a scene was performed by re-projection of the pixel points from multiple image samples with a single centre of projection. This was done using sparse bundle adjustment algorithm. The statistical summary obtained after the application of this algorithm provides a gauge for the efficiency of the optimisation step. The optimised data was then visualised in Meshlab software environment, hence providing the reconstructed scene. Secondly, with any of the well-established camera arrangements, all cameras are usually constrained to the same horizontal plane. Therefore, occlusion becomes an extremely challenging problem, and a robust camera set-up is required in order to resolve strongly the hidden part of any scene objects. To adequately meet the visibility condition for scene objects and given that occlusion of the same scene objects can occur, a multi-plane camera structure is highly desirable. Therefore, this thesis also explore trapezoidal camera structure for image acquisition. The approach here is to assess the feasibility and potential of several physical cameras of the same model being sparsely arranged on the edge of an efficient trapezoid graph. This is implemented both Matlab and Maya. The quality of the depth maps rendered in Matlab are better in Quality

Calibration, selection and mosaicing of SMART-1 AMIE images

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e de ComputadoresSmall Missions for Advanced Research in Technology (SMART-1), represented European Space Agency (ESA) first mission to the moon. It fulfilled the goal of improving the scientific knowledge of earth’s natural satellite, while testing new technologies that had never been used in space exploration. Among the on board instruments of SMART-1 was the Advanced Moon micro-Imager Experiment (AMIE). It was an imaging equipment whose mission was to map the lunar surface providing state-of-the-art resolution. Containing six filters inside its visual scope AMIE allowed the study of the surface composition by multispectral imaging. This thesis aims at building a set of maps covering approximately all the Moon surface as it was mapped by the SMART-1 spacecraft, using the 31945 images captured by the AMIE instrument. During the Earth escape phase the instrument’s CCD was damaged by radiation, causing the accumulation of dark current and invalidating the laboratorial image calibration algorithm. The acquired dataset also suffered from scattered light that got beneath the CCD filters and reduced their contrast. In order to overcome this problem, a new calibration procedure was developed using the in-flight collected data and theoretical models, as well as a method to compensate for the reduced contrast in the filters. For building the lunar maps, the images were individually analysed and classified accordingly to their visual quality and grouped by their illumination conditions, allowing the creation of visually balanced maps. Image mosaicing and projection techniques were used to compensate the geometrical distortions and compose the calibrated images into a set of 88 maps of the Moon. Increasing the flexibility of the process, a comprehensive tool that allows the edition of the images in the mosaiced maps, as well as brightness and contrast correction and adjustment is also presented

Heterogeneous sensor database framework for the sensor observation service: integrating remote and in-situ sensor observations at the database backend

Dissertation submitted in partial fulfillment of the requirements for the Degree of Master of Science in Geospatial Technologies.Environmental monitoring and management systems in most cases deal with models and spatial analytics that involve the integration of in-situ and remote sensor observations. In-situ sensor observations and those gathered by remote sensors are usually provided by different databases and services in real-time dynamic service systems like the Geo-Web Services. Thus, data have to be pulled from different databases and transferred over the web before they are fused and processed on the service middleware. This process is very massive and unnecessary communication and work load on the service, especially when retrieving massive raster coverage data. Thus in this research, we propose a database model for heterogeneous sensortypes that enables geo-scientific processing and spatial analytics involving remote and in-situ sensor observations at the database level of the Sensor Observation Service, SOS. This approach would be used to reduce communication and massive workload on the Geospatial Web Service, as well make query request from the user end a lot more flexible. Hence the challenging task is to develop a heterogeneous sensor database model that enables geoprocessing and spatial analytics at the database level and how this could be integrated with the geo-web services to reduce communication and workload on the service and as well make query request from the client end more flexible through the use of SQL statements