To see the other types of publications on this topic, follow the link: Mars craters.
Dissertations / Theses on the topic 'Mars craters'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 48 dissertations / theses for your research on the topic 'Mars craters.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
De, Villiers Germari Marzen Luke J. King David T. "Remote sensing of shallow-marine impact craters on Mars." Auburn, Ala., 2007. http://hdl.handle.net/10415/1343.
Full text
2
Kukkonen, S. (Soile). "Small impact craters in crater counting:evolution studies of the eastern Hellas outflow channels, Mars." Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526218779.
Full textAbstract:
Abstract Crater counting is a method which allows us to estimate the surface ages of the planetary bodies, from which the sampling and sample delivery to laboratories on Earth are difficult or impossible. Because the number of craters on a surface unit increases over the time the surface has been exposed to space, old, geologically stable units have more craters than young and active units. When the crater production rate as a function of time is known, the absolute age of the surface unit can be determined based on its crater density. The purpose of this thesis is to investigate the role of small impact craters in crater counts to find out how modern very high-resolution space images can be utilized in age determination of planetary surfaces. The thesis focuses on how reliable crater count based datings are, if only small craters and counting areas are used in age determination. The research is carried out by utilizing crater counts on the outflow channels of Dao, Niger, Harmakhis and Reull Valles, which all are located in the eastern rim region of the Hellas impact basin, on the southern hemisphere of Mars. Crater counts are performed mainly based on the images of ConTeXt Imager (CTX) and High Resolution Imaging Science Experiment (HiRISE) aboard Mars Reconnaissance Orbiter (MRO). The results show that small craters are a very valuable tool to get information about the surface age. Instead of the size-range of counted craters, or the size of counting areas, results are dependent on the variability and scale of the surface modification history. The more variable or larger scale the modification history is, the larger surface area and wider crater diameter range are typically needed to achieve comprehensive age estimations. The crater counts on the eastern Hellas outflow channels support the earlier theories according to which the valles formed during a relatively short time interval, ~ 3.4–3.7 Ga ago. The existence of terrace structures and smaller tributary channels indicate that the outflow channels were filled by several pulses of liquids. The major fluvial activity ended no later than ~ 0.8–1.9 Ga ago, and it was probably controlled by the activity of nearby highland volcanoes. Soon after the declined fluvial activity, the outflow channels were covered by ice-rich deposits. The major reason for this was probably the changed climatic conditions, although in places e.g. impact cratering seems to have contributed to the emplacement of the deposits. The region as a whole was also resurfaced several times because of changes in local climate conditions. The most significant of the resurfacing processes seem to be the episodes of thin ice-rich mantling deposits, the most recent of which dominated the regional modification less than 10 Ma ago. In addition, the region has experienced eolian activity during the last 1 MaOriginal papers The original publications are not included in the electronic version of the dissertation. Kostama, V.-P., Kukkonen, S., & Raitala, J. (2017). Resurfacing event observed in Morpheos basin (Eridania Planitia) and the implications to the formation and timing of Waikato and Reull Valles, Mars. Planetary and Space Science, 140, 35–48. https://doi.org/10.1016/j.pss.2017.04.001 Kukkonen, S., & Kostama, V.-P. (2018). Modification history of the Harmakhis Vallis outflow channel, Mars, based on CTX-scale photogeologic mapping and crater count dating. Icarus, 299, 46–67. https://doi.org/10.1016/j.icarus.2017.07.014 Kukkonen, S., & Kostama, V.-P. (2018). Usability of small impact craters on small surface areas in crater count dating: Analysing examples from the Harmakhis Vallis outflow channel, Mars. Icarus, 305, 33–49. https://doi.org/10.1016/j.icarus.2018.01.004 Kukkonen, S., & Kostama, V.-P. (2018). Mapping and dating based evolution studies of the Niger Vallis outflow channel, Mars. Planetary and Space Science, 153, 54–71. https://doi.org/10.1016/j.pss.2017.12.012 Korteniemi, J., & Kukkonen, S. (2018). Volcanic Structures Within Niger and Dao Valles, Mars, and Implications for Outflow Channel Evolution and Hellas Basin Rim Development. Geophysical Research Letters, 45(7), 2934–2944. https://doi.org/10.1002/2018gl077067 http://jultika.oulu.fi/Record/nbnfi-fe201902226008
3
Chee, Yenlai. "Remote sensing analysis of cratered surfaces Mars landing hazard assessment, comparison to terrestrial crater analogs, and Mars crater dating models /." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2007. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
Full text
4
BARLOW, NADINE GAIL. "RELATIVE AGES AND THE GEOLOGIC EVOLUTION OF MARTIAN TERRAIN UNITS (MARS, CRATERS)." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184013.
Full textAbstract:
Existing martian relative age chronologies rely entirely or predominantly on Mariner 9 images, extrapolated numbers of craters, and craters 500(DEGREES)K) for the planet are consistent with the derived chronology.
5
Daubar, Ingrid Justine. "New Dated Craters On Mars And The Moon: Studies Of The Freshest Craters In The Solar System." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/337303.
Full textAbstract:
New, dated impacts discovered on Mars and the Moon provide direct observations of modern bombardment in the inner Solar System and the freshest available examples of recent craters. Their population, morphology, formation and modification processes relate to issues with secondaries and help calibrate cratering chronology models. I use a subset of the new impacts to measure the current production function at Mars. The resulting production function is a factor of approximately four lower than widely-used models, and the size frequency distribution has a shallower slope. This discrepancy between the measured current impact flux and model predictions could be due to many issues, so craters <~50m diameter should not be used for crater age dating unless the uncertainties are understood. I find that these new martian craters are only slightly deeper on average than the expected depth/diameter ratio (d/D) of ~0.2 for simple primaries; the majority would not be mistaken for secondaries based on d/D. A wide spread in d/D indicates that impact conditions or target properties might influence final crater morphologies at these sizes. Extended low-albedo features surround these new craters, presumed to have formed when the impact blast disturbed a surface coating of high-albedo dust, exposing a darker substrate. Some of these features changed drastically over a few Mars years, however, half of the sites show no changes at all. Estimated fading lifetimes cluster around ~7 Mars years. Controls on the amount and rates of fading have yet to be determined. These results show that the current impact production function is not under-sampling new impacts due to fading prior to detection. New craters have also been discovered on the Moon, using similar techniques. Five new impact craters were found that formed within the last ~40 years. Conclusions are unreliable with only these scant statistics, but preliminary comparisons indicate they follow the expected size frequency distribution predicted by the Neukum [1983; Neukum et al., 2001] production function and chronology. This also leads to a very preliminary measurement of the current Moon/Mars cratering ratio at a single diameter, which falls below models by only a factor of approximately six.
6
Bamberg, Marlene. "Planetary mapping tools applied to floor-fractured craters on Mars." Phd thesis, Universität Potsdam, 2014. http://opus.kobv.de/ubp/volltexte/2014/7210/.
Full textAbstract:
Planetary research is often user-based and requires considerable skill, time, and effort. Unfortunately, self-defined boundary conditions, definitions, and rules are often not documented or not easy to comprehend due to the complexity of research. This makes a comparison to other studies, or an extension of the already existing research, complicated. Comparisons are often distorted, because results rely on different, not well defined, or even unknown boundary conditions.
The purpose of this research is to develop a standardized analysis method for planetary surfaces, which is adaptable to several research topics. The method provides a consistent quality of results. This also includes achieving reliable and comparable results and reducing the time and effort of conducting such studies. A standardized analysis method is provided by automated analysis tools that focus on statistical parameters. Specific key parameters and boundary conditions are defined for the tool application. The analysis relies on a database in which all key parameters are stored. These databases can be easily updated and adapted to various research questions. This increases the flexibility, reproducibility, and comparability of the research. However, the quality of the database and reliability of definitions directly influence the results. To ensure a high quality of results, the rules and definitions need to be well defined and based on previously conducted case studies. The tools then produce parameters, which are obtained by defined geostatistical techniques (measurements, calculations, classifications).
The idea of an automated statistical analysis is tested to proof benefits but also potential problems of this method. In this study, I adapt automated tools for floor-fractured craters (FFCs) on Mars. These impact craters show a variety of surface features, occurring in different Martian environments, and having different fracturing origins. They provide a complex morphological and geological field of application. 433 FFCs are classified by the analysis tools due to their fracturing process. Spatial data, environmental context, and crater interior data are analyzed to distinguish between the processes involved in floor fracturing.
Related geologic processes, such as glacial and fluvial activity, are too similar to be separately classified by the automated tools. Glacial and fluvial fracturing processes are merged together for the classification. The automated tools provide probability values for each origin model. To guarantee the quality and reliability of the results, classification tools need to achieve an origin probability above 50 %. This analysis method shows that 15 % of the FFCs are fractured by intrusive volcanism, 20 % by tectonic activity, and 43 % by water & ice related processes. In total, 75 % of the FFCs are classified to an origin type. This can be explained by a combination of origin models, superposition or erosion of key parameters, or an unknown fracturing model. Those features have to be manually analyzed in detail. Another possibility would be the improvement of key parameters and rules for the classification.
This research shows that it is possible to conduct an automated statistical analysis of morphologic and geologic features based on analysis tools. Analysis tools provide additional information to the user and are therefore considered assistance systems.Planetenforschung umfasst oft zeitintensive Projekte, bei denen Expertise und Erfahrung eine wesentliche Rolle spielen. Auf Grund äusserst komplexer und sich selten wiederholender Forschungsfragen sind Annahmen, Definitionen und Regeln zur Lösung dieser Fragen nicht leicht nachvollziehbar oder aber nicht eindeutig dokumentiert. Ein Vergleich der Ergebnisse unterschiedlicher Forscher zum selben Thema oder eine Erweiterung der Forschungsfrage macht dies somit nur schwer möglich. Vergleiche liefern oftmals verzerrte Ergebnisse, da die Ausgangslage und Randbedingungen unterschiedlich definiert worden sind. Das Ziel dieser Arbeit ist es eine Standardmethode zur Oberflächenanalyse zu entwickeln, die auf zahlreiche Untersuchungsfragen angewandt werden kann. Eine gleichbleibende Qualität der Ergebnisse muss durch diese Methode gewährleistet sein. Ein weiteres Ziel ist es, dass diese Methode ohne Vorwissen und Expertise angewandt werden kann und die Ergebnisse in kurzer Zeit vorliegen. Ausserdem müssen die Ergebnisse vergleichbar und nachvollziehbar sein. Automatisch operierende Analysewerkzeuge können die zahlreichen Anforderungen erfüllen und als Standardmethode dienen. Statistische Ergebnisse werden durch diese Methode erzielt. Die Werkzeuge basieren auf vordefinierten, geowissenschaftlichen Techniken und umfassen Messungen, Berechnungen und Klassifikationen der zu untersuchenden Oberflächenstrukturen. Für die Anwendung dieser Werkzeuge müssen Schlüsselstrukturen und Randbedingungen definiert werden. Des Weiteren benötigen die Werkzeuge eine Datenbank, in der alle Oberflächenstrukturen, aber auch Informationen zu den Randbedingungen gespeichert sind. Es ist mit geringem Aufwand möglich, Datenbanken zu aktualisieren und sie auf verschiedenste Fragestellungen zu adaptieren. Diese Tatsache steigert die Flexibilität, Reproduzierbarkeit und auch Vergleichbarkeit der Untersuchung. Die vordefinierten Randbedingungen und die Qualität der Datenbank haben jedoch auch direkten Einfluss auf die Qualität der Ergebnisse. Um eine gleichbleibend hohe Qualität der Untersuchung zu gewährleisten muss sichergestellt werden, dass alle vordefinierten Bedingungen eindeutig sind und auf vorheriger Forschung basieren. Die automatisch operierenden Analysewerkzeuge müssen als mögliche Standardmethode getestet werden. Hierbei geht es darum Vorteile, aber auch Nachteile zu identifizieren und zu bewerten. In dieser Arbeit werden die Analysewerkzeuge auf einen bestimmten Einschlagskratertyp auf dem Mars angewandt. Krater mit zerbrochenen Kraterböden (Floor-Fractured Craters) sind in verschiedensten Regionen auf dem Mars zu finden, sie zeigen zahlreiche Oberflächenstrukturen und wurden durch unterschiedliche Prozesse geformt. All diese Fakten machen diesen Kratertyp zu einem interessanten und im geologischen und morphologischen Sinne sehr komplexen Anwendungsgebiet. 433 Krater sind durch die Werkzeuge analysiert und je nach Entstehungsprozess klassifiziert worden. Für diese Analyse sind Position der Krater, Art des Umfeldes und Strukturen im Kraterinneren ausschlaggebend. Die kombinierten Informationen geben somit Auskunft über die Prozesse, welche zum Zerbrechen des Kraterbodens geführt haben. Die entwickelten Analysewerkzeuge können geologische Prozesse, die sehr ähnlich zueinander sind, von einander abhängig sind und zusätzlich auch dieselben Oberflächenstrukturen formen, nicht eindeutig unterscheiden. Aus diesem Grund sind fluviale und glaziale Entstehungsprozesse für den untersuchten Kratertyp zusammengefasst. Die Analysewerkzeuge liefern Wahrscheinlichkeitswerte für drei mögliche Entstehungsarten. Um die Qualität der Ergebnisse zu verbessern muss eine Wahrscheinlichkeit über 50 % erreicht werden. Die Werkzeuge zeigen, dass 15 % der Krater durch Vulkanismus, 20 % durch Tektonik und 43 % durch Wasser- und Eis-bedingte Prozesse gebildet wurden. Insgesamt kann für 75 % des untersuchten Kratertyps ein potentieller Entstehungsprozess zugeordnet werden. Für 25 % der Krater ist eine Klassifizierung nicht möglich. Dies kann durch eine Kombination von geologischen Prozessen, einer Überprägung von wichtigen Schlüsselstrukturen, oder eines bisher nicht berücksichtigten Prozesses erklärt werden. Zusammenfassend ist zu sagen, dass es möglich ist planetare Oberflächenstrukturen quantitativ durch automatisch operierende Analysewerkzeuge zu erfassen und hinsichtlich einer definierten Fragestellung zu klassifizieren. Zusätzliche Informationen können durch die entwickelten Werkzeuge erhalten werden, daher sind sie als Assistenzsystem zu betrachten.
7
Perälä, Jesper. "Pit Craters of Arsia Mons Volcano, Mars, and Their Relation to Regional Volcano-tectonism." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-255563.
Full textAbstract:
Pit crater and pit crater chains associated to the volcano Arsia Mons on Mars have been mapped to analyse their spatial pattern and to conclude about their formation. For the mapping, high resolution satellite data gathered during the Mars Express mission were used. The spatial distribution of the pit craters was then compared with typical patterns of magmatic sheet intrusions within volcanoes as they are known from Earth. The results show that the pattern of the mapped pit craters and pit crater chains are in good agreement with these sheet intrusions and are therefore likely related to Martian sheet intrusions.Kollapskratrar och kraterkedjor relaterade till vulkanen Arsia Mons på Mars har karterats för att analysera deras spatiala mönster och för att komma till slutsatser för deras tillblivelse. Högupplösta satellitbilder tagna av Mars Express-sonden har använts för karteringen. Fördelningen av de karterade kraterkedjorna jämfördes med typiska fördelningar av magmatiska gångbergarter från vulkaner på jorden. Resultaten visar att fördelningen av kollapskratrar och kraterkedjor överensstämmer enligt förväntningarna och påvisar en relation mellan kollapskratrar och magmatiska gångbergarter på Mars.
8
Viola, Donna, and Donna Viola. "Expanded Craters on Mars: Implications for Shallow, Mid-Latitude Excess Ice." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625594.
Full textAbstract:
Understanding the age and distribution of shallow ice on Mars is valuable for interpreting past and present climate conditions, and has implications on habitability and future in situ resource utilization. Many ice-related features, such as lobate debris aprons and concentric crater fill, have been studied using a range of remote sensing techniques. Here, I explore the distribution of expanded craters, a form of sublimation thermokarst where shallow, excess ice has been destabilized and sublimated following an impact event. This leads to the collapse of the overlying dry regolith to produce the appearance of diameter widening. The modern presence of these features suggests that excess ice has remained preserved in the terrain immediately surrounding the craters since the time of their formation in order to maintain the surface. High-resolution imagery is ideal for observing thermokarst features, and much of the work described here will utilize data from the Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO). Expanded craters tend to be found in clusters that emanate radially from at least four primary craters in Arcadia Planitia, and are interpreted as secondary craters that formed nearly simultaneously with their primaries. Crater age dates of the primaries indicate that the expanded secondaries, as well as the ice layer into which they impacted, must be at least tens of millions of years old. Older double-layer ejecta craters in Arcadia Planitia commonly have expanded craters superposed on their ejecta – and they tend to be more expanded (with larger diameters) in the inner ejecta layer. This has implications on the formation mechanisms for craters with this unique ejecta morphology. Finally, I explore the distribution of expanded craters south of Arcadia Planitia and across the southern mid-latitudes, along with scalloped depressions (another form of sublimation thermokarst), in order to identify the modern excess ice boundary in this region and any longitudinal variations. This study identifies some potential low-latitude locations with patchy excess ice, possibly preserved during a past climate. Through these studies, I will infer regions that contain abundant ice today and consider the implications that this ice has on both the martian climate and future exploration.
9
Breton, Sylvain. "Dynamique des surfaces planétaires actives : quantification des paysages, modélisation et inversion." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1280.
Full textAbstract:
Les cratères d'impact sont indispensables dans l'étude des surfaces planétaires. D'une part, les statistiques de leur nombre permet de dater les surfaces planétaires, d'autre part, leur forme révèle les processus de surface qu'ils ont connu. Cette thèse propose de coupler les études statistiques et morphologiques afin d'étudier la temporalité et l'importance des processus sédimentaires et/ou volcaniques des surfaces planétaires. L'utilisation de la profondeur des cratères permet de rajouter une dimension aux distributions avec l'introduction des distributions en fréquence de taille et de profondeur (SDFD), offrant ainsi un aperçu des modifications morphologiques des cratères. Nous avons développé en conséquence des modèles permettant de modéliser l'évolution d'une population de cratères en prenant en compte les phénomènes d'oblitération. La surface Mars est largement cratérisée, mais ils ont pour la plupart été fortement modifiés par des processus volcaniques et/ou sédimentaires. A partir des SDFDs, nous avons estimé les taux d'oblitération martiens à une échelle globale. Ces taux sont, au Noachien, de plusieurs milliers de m/Ga, mais décroissent rapidement dès l'Hespérien inférieur et sont proches de 0 à l'Amazonien. L'oblitération sur la province de Tharsis a décru beaucoup moins rapidement suggérant une persistance du volcanisme à l'Amazonien inférieur. Les plaines du nord à l'Amazonien sont marqué par des taux d'oblitération un ordre de grandeur au-dessus du reste de la planète, qui pourraient indiquer la mise en place continue de la Vastitas Borealis Formation au cours de l'Amazonien moyen. En complément de notre approche à l'échelle globale, nous avons déterminé des taux d'oblitération actuels à partir de cartographies de cratères réalisées à haute résolution spatiale sur des sites d'atterrissage de rovers actuels et futurs. Les sites de Mawrth Vallis et d'Oxia Planum présentent les taux d'oblitération actuels les plus importants en particulier au niveau de leurs unités geologiques riches en minéraux hydratésImpact crater are often used in the study of planetary surfaces. On the one hand, statistics on crater number provide the age of the surface, on the other hand, their shapes reflect the surface processes they witnessed. This study combines the statistic and morphology approaches in order to investigate the timing and intensity of sedimentary and volcanic processes of planetary surfaces. The use of crater depth measurements add a dimension to frequency distributions with the introduction of size and depth frequency distribution (SDFD). SDFSs can be interpreted in term of crater obliteration rates thanks to crater chronology models. We also developed models of crater population taking into account obliteration. Mars surface is highly cratered with many craters displaying signs of modifications by volcanic process, sedimentation and erosion. We interpreted SDFDs using a classic crater chronology system, to produce global maps of obliteration at different epochs of Mars. During Noachian, obliteration rates reach several thousands m/Gy, but rapidly decrease during early Hesperian and are close to 0 during Amazonian. Obliteration on the province of Tharsis decreased slower, suggesting a persistence of volcanic activity until early Amazonian. Northern lowlands witness Amazonian obliteration rates one order of magnitude higher than the rest of the planet, which may indicate the continuous formation of Vastitas Borealis during middle Amazonian. In addition to our global approach, we computed recent obliteration rates from mapping of high resolution images on landing sites of rover missions. Mawrth Vallis and Oxia Planum present significant obliteration rates, especially on units containing hydrated minerals
10
Viola, D., and A. S. McEwen. "Geomorphological Evidence for Shallow Ice in the Southern Hemisphere of Mars." AMER GEOPHYSICAL UNION, 2018. http://hdl.handle.net/10150/627126.
Full textAbstract:
The localized loss of near-surface excess ice on Mars by sublimation (and perhaps melting) can produce thermokarstic collapse features such as expanded craters and scalloped depressions, which can be indicators of the preservation of shallow ice. We demonstrate this by identifying High Resolution Imaging Science Experiment images containing expanded craters south of Arcadia Planitia (25-40 degrees N) and observe a spatial correlation between regions with thermokarst and the lowest-latitude ice-exposing impact craters identified to date. In addition to widespread thermokarst north of 35 degrees N, we observe localized thermokarst features that we interpret as patchy ice as far south as 25 degrees N. Few ice-exposing craters have been identified in the southern hemisphere of Mars since they are easier to find in dusty, high-albedo regions, but the relationship among expanded craters, ice-exposing impacts, and the predicted ice table boundary in Arcadia Planitia allows us to extend this thermokarst survey into the southern midlatitudes (30-60 degrees S) to infer the presence of ice today. Our observations suggest that the southern hemisphere excess ice boundary lies at 45 degrees S regionally. At lower latitudes, some isolated terrains (e.g., crater fill and pole-facing slopes) also contain thermokarst, suggesting local ice preservation. We look for spatial relationships between our results and surface properties (e.g., slope and neutron spectrometer water ice concentration) and ice table models to understand the observed ice distribution. Our results show trends with thermal inertia and dust cover and are broadly consistent with ice deposition during a period with a higher relative humidity than today. Shallow, lower-latitude ice deposits are of interest for future exploration.
11
Bart, Gwendolyn Diane. "Lunar Surface Geology From Analysis of Impact Craters and Their Ejecta." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/193987.
Full textAbstract:
Analysis of impact craters and their ejecta addresses someunanswered questions about the lunar surface. First I estimatethe regolith depth on the south farside of the Moon to be about40 m, which is significantly deeper than the nearside regolith,estimated to be 3-16 m. This result is obtained by studyinghundred meter diameter flat floored craters, using the method ofQuaide and Oberbeck (J. Geophys. Res., 1968, 73, 5247-5270). This measurement has implications for the formation of the lunarregolith, and for interpretation of samples returned in thefuture by astronauts or automated sample return missions.Next, I report the discovery of a method that distinguishesbetween primary and distant secondary craters in high resolutionplanetary images. For a given crater size, the largest bouldersof secondary craters are significantly larger than those ofprimary craters. The ability to identify distant secondarycraters will help constrain primary production rates of smallcraters and improve surface age determination of small areasbased on small crater counts.Third, I characterize the distributions of boulders ejected from18 lunar impact craters. I find that in large craters, thelargest boulders are preferentially ejected at low velocities(closer to the crater), whereas the largest boulders from smallcraters are ejected over a wider range of ejection velocities. Also, for a given crater size, deeper regolith reduces themaximum ejection velocity attained by a boulder ejected from acrater. I show that this is a logical result of the streamlinesof excavation in an impact when there are no coherent boulders inthe regolith. Cumulative plots of the boulders have slopessteeper than -2, as do secondary craters. This result isexpected because ejecta fragments produce secondary craters.Finally, I describe the morphology of some lunar crater walllandslides that strongly resemble martian gullies, despite thelack of geologically active water on the Moon today or in thepast. The lunar features indicate that alcove-channel-apronmorphology, attributed on Mars to seepage of liquid water, canalso form via a dry landslide mechanism. Therefore alcove-channel-apron morphology is not diagnostic of water carvedgullies.
12
Bamberg, Marlene [Verfasser], and Hartmut [Akademischer Betreuer] Asche. "Planetary mapping tools applied to floor-fractured craters on Mars / Marlene Bamberg. Betreuer: Hartmut Asche." Potsdam : Universitätsbibliothek der Universität Potsdam, 2014. http://d-nb.info/1064159745/34.
Full text
13
Wyant, Michael Anthony DeFrancesco. "BURIED IMPACT STRUCTURES IN THE MarsCrust-3 CRUSTAL THICKNESS MODEL: IDENTIFICATION, CLASSIFICATION, AND SIGNIFICANCE." Master's thesis, Temple University Libraries, 2011. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/120503.
Full textAbstract:
GeologyM.S.
The addition of buried impact structures to the known database of surface structures is key to a complete understanding of the geologic history of Mars because it allows for a more precise calculation of crustal age. Also, because these buried structures record an impact event and a resurfacing event they can be used to clearly define crustal versus surface ages. This study used topographic data and a crustal thickness model to identify buried and visible impact structures. This process was repeated twice and then correlated to create a global database of impact structures greater than 200 km. During the study confidence factor protocol was developed based on [1] ratio of crater diameter to relief and [2] percentage of rim present. This criteria was applied to each visible and buried structure. The comparison of visible and buried impact structures provides constraints on the timing of resurfacing events. Cumulative and N(300) values were calculated to derive the relative crustal ages in major geologic provinces. It was found that [1] the Martian lowlands and highlands have similar crustal ages when combining the visible and buried impact structures, [2] Tharsis is younger than these two regions, [3] the lowlands appear to have been thinned before or during the Late Heavy Bombardment (LBH), and [4] the resurfacing of the lowlands must have happened at the same time or shortly after the rise of the Tharsis bulge.
Temple University--Theses
14
Landis, Margaret E., Shane Byrne, Ingrid J. Daubar, Kenneth E. Herkenhoff, and Colin M. Dundas. "A revised surface age for the North Polar Layered Deposits of Mars." AMER GEOPHYSICAL UNION, 2016. http://hdl.handle.net/10150/615108.
Full textAbstract:
The North Polar Layered Deposits (NPLD) of Mars contain a complex stratigraphy that has been suggested to retain a record of past eccentricity- and obliquity-forced climate changes. The surface accumulation rate in the current climate can be constrained by the crater retention age. We scale NPLD crater diameters to account for icy target strength and compare surface age using a new production function for recent small impacts on Mars to the previously used model of Hartmann (2005). Our results indicate that ice is accumulating in these craters several times faster than previously thought, with a 100m diameter crater being completely infilled within centuries. Craters appear to have a diameter-dependent lifetime, but the data also permit a complete resurfacing of the NPLD at similar to 1.5 ka.
15
Tirsch, Daniela [Verfasser]. "Dark Dunes on Mars : Analyses on origin, morphology, and mineralogical composition of the dark material in Martian craters / Daniela Tirsch." Berlin : Freie Universität Berlin, 2009. http://d-nb.info/102349843X/34.
Full text
16
Lotti, Alex. "Distribuzione e genesi di pit craters in due diverse regione vulcaniche di Marte (Pavonis-Ascraeus Montes ed Elysium Mons)." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21797/.
Full textAbstract:
Osservazioni e analisi preliminari sono estremamente importanti per pianificare una missione spaziale, in particolare quelle che devono atterrare su corpi celesti, per poter definire gli itinerari dei luoghi da analizzare ed esplorare una volta raggiunta la superficie.
Questa tesi è volta ad un’analisi sulle differenze e similitudini di due regioni di Marte, Pavonis-Ascraeus Montes ed Elysium Mons, con lo scopo di analizzare la presenza di cavità di collasso denominate “pit” sotto diversi aspetti morfologici e di distribuzione ed eventualmente dare spunti per analisi più nel dettaglio o siti di analisi sul suolo marziano. I pit presi in considerazione sono forniti dalla lista del “Mars Global Cave Candidate Catalog” (MGC3). Per mezzo delle immagini satellitari è stato definito su quali terreni e con quale disposizione rispetto alle altre strutture regionali (forme tettoniche o vulcaniche) si trovano i pit analizzati. Lo studio ha mostrato che le stesse tipologie di pit si incontrano in entrambe le zone vulcaniche analizzate, con una prevalenza di cavità legate a tubi lavici in Elysium Mons.
17
Lagain, Anthony. "Reconstitution du flux d'impact et des variations paléoclimatiques martiennes par la datation des cratères à éjecta lobés." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS430/document.
Full textAbstract:
Le comptage de cratères sur une surface planétaire est à l’heure actuelle le seul moyen de préciser la temporalité des événements ayant marqué l’histoire des corps telluriques. Cette technique nécessite de connaitre précisément le taux avec lequel se forme les cratères d’impact, c'est-à-dire le flux d’impact, mais aussi son évolution en fonction du diamètre des cratères, la fonction de production. Ensemble, ces deux variables forment le système de chronologie d’un corps planétaire. Il est relativement bien contraint entre 3,9 et 3,5 milliards d’années avant notre ère et considéré comme constant depuis 3 milliards d’années, une hypothèse remise en cause par des observations lunaires et terrestres. Les cratères d’impact à éjecta lobés sont très nombreux sur Mars. Leur morphologie traduit la présence d’une grande quantité de glace d’eau dans le sous-sol au moment de l’impact. La variation spatio-temporelle de cette couche est très peu contrainte. Celle-ci est principalement influencée par l’obliquité de la planète. Leurs nappes d’éjecta sont continues et constituent donc des surfaces idéales pour dater leur formation. L’objectif de cette thèse est de mieux contraindre la chronologie martienne et la variation de l’extension de la couche de volatiles présente sous la surface de Mars responsable de telles morphologies. Par la datation de la mise en place d’une population de cratères à éjecta lobés situés sur Acidalia Planitia, il a été possible de comparer leur fréquence de formation avec le flux d’impact qui a été utilisé pour les dater. Un important désaccord entre nos données et le modèle à flux constant a pu être observé. Un test d’autocohérence entre le flux d’impact mesuré et le flux utilisé pour dater chaque cratère a permis de montrer que le taux d’impact le plus en accord avec nos données était celui présentant un pic de cratérisation entre 0,5 milliards d’années et la période actuelle. Ce pic est associé à deux collisions dans la ceinture principale d’astéroïdes. Néanmoins, cette méthode inverse est soumise à un problème logique mis en évidence par la simulation d’une population de cratères synthétiques. Il apparaît à posteriori que la variable temporelle de la chronologie martienne doit être la fonction de production des cratères d’une centaine de mètres de diamètre. Ces résultats modifient profondément l’âge des surfaces martiennes qui peuvent être mesurés par comptage de cratères. La datation de l’ensemble des cratères martiens dont les nappes d’éjecta lobés sont très étendues a permis également de mettre en évidence une augmentation de l’âge de ces cratères avec la diminution en latitude. Nous avons interprété ces observations comme étant le résultat de l’évolution récente de l’extension de la couche riche en volatils sous la surface de Mars, en lien avec la variation de l’obliquité de la planète. En effet, une diminution de l’angle d’obliquité de Mars il y a 4 millions d’années a restreint l’extension de la couche de volatils à haute latitude. Le lien étroit entre la localisation de ces cratères et leurs âges a permis de poser certaines conditions quant à l’évolution possible de l’obliquité martienne sur les 80 derniers millions d’années. Enfin, la révision de la base de données de cratères martiens la plus complète à ce jour au moyen d’une interface accessible à tous a permis de créer le premier catalogue de cratères adapté à la datation de surfaces martiennes. Nous avons pour cela mis en place une classification des cratères permettant l’exclusion, lors d’une datation, des cratères de type secondaire, fantôme ainsi que des fausses détections contenus dans la base de donnée originelleCounting craters on planetary surfaces is currently the only way to precise the events temporality which have marked the history of terrestrial bodies. This technique requires the precise knowledge of the rate with which impact craters are emplaced over time, the impact flux, but also its evolution in function of crater diameter, the production function. Together, these two variables constitute the chronology system of a planetary body. This system is relatively well constrained between 3,9 and 3,5 billion years before present and considered to be constant since 3 billion years, a hypothesis challenged by earthly and lunar observations. Layered ejecta craters are numerous on Mars. Their morphology is related to the presence of ice-rich material in the subsurface at the moment of the impact. The spatial and temporal evolution of this layer is poorly constrained. This one is primarily influenced by the obliquity of Mars. Their ejecta blankets are continuous and therefore constitute ideal surfaces to date the impact itself. The purpose of this thesis is to better constraint the Martian chronology and to better understand the variation of volatiles layer extent present under the surface of Mars. By the dating of the formation of a layered ejecta crater population located on Acidalia Planitia, it has been possible to compare the emplacement frequency of these structures with the impact flux that has been used to date them. An important mismatch between our data and the constant flux has been noted. An auto-consistency test between the measured impact rate and the rate used to date each crater has shown that the most consistent flux with our data is a cratering spike between 0,5 billion years and the actual period. This spike is associated to two main asteroid break-ups in the main asteroid belt. Nevertheless, this inverse method is challenged by a logical problem highlighted by the simulation of a synthetic population of craters. It appears a posteriori that the temporal fluctuation of the Martian chronology comes from the production function of impact craters of hundred meters of diameter. These results modify considerably the age of the Martian surface that we can measure by counting craters. The dating of all craters which exhibits a high extent of their ejecta blankets has also allowed to highlight an increasing of their age with the decreasing of the latitude. We have interpreted this observation by the result of the late evolution of the volatiles layer extent under the surface of Mars, linked to the shift of the obliquity. A decreasing of the Martian obliquity angle there was 4 million years ago has restricted the volatiles layer extent to high latitude. The close link between the location of these craters and their ages has allowed us to set some conditions of possible evolution of the Martian obliquity during the last 80 Myrs. Finally, the correction of the most complete Martian crater database thanks to a web interface accessible to everyone has allowed to create the first crater catalogue adapted to the martian surface dating. We have developed a crater classification allowing the exclusion, during a surface dating, of secondary craters, ghosts craters as well as false detections contained in the original database
18
Dolan, Daniel J. "Structural Evolution of Martin Crater Thaumasia Planum, Mars." Thesis, California State University, Long Beach, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10606452.
Full textAbstract:
A detailed structural map of the central uplift of Martin Crater in western Thaumasia Planum, Mars, reveals highly folded and fractured geology throughout the 15-km diameter uplift. The stratigraphy in the central uplift of the crater has been rotated to near vertical dip and imaged by high-definition cameras aboard the Mars Reconnaissance Orbiter (MRO). These unique factors allow individual geologic beds in Martin Crater to be studied and located across the length of the uplift.
Bedding in Martin Crater primarily strikes SSE-NNW and dips near vertically. Many units are separated by a highly complex series of linear faults, creating megablocks of uplifted material. Faulting is dominantly left-slip in surface expression and strikes SW-NE, roughly perpendicular to bedding, and major fold axes plunge toward the SW. Coupled with infrared imagery of the ejecta blanket, which shows an “exclusion zone” northeast of the crater, these structural indicators provide strong support for a low-angle impactor (approximately 10–20°) originating from the northeast.
Acoustic fluidization is the prevailing theoretical model put forth to explain complex crater uplift. The theory predicts that uplifted megablocks in craters are small, discrete, separated and highly randomized in orientation. However, megablocks in Martin Crater are tightly interlocked and often continuous in lithology across several kilometers. Thus, the model of acoustic fluidization, as it is currently formulated, does not appear to be supported by the structural evidence found in Martin Crater.
19
Westbrook, Owen William. "Crater ice deposits near the south pole of Mars." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53113.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2009.Includes bibliographical references (p. 55-60).
Layered deposits atop both Martian poles are thought to preserve a record of past climatic conditions in up to three km of water ice and dust. Just beyond the extent of these south polar layered deposits (SPLD), dozens of impact craters contain large mounds of fill material with distinct similarities to the main layered deposits. Previously identified as outliers of the main SPLD, these deposits could offer clues to the climatic history of the Martian south polar region. We extend previous studies of these features by cataloging all crater deposits found near the south pole and quantifying the physical parameters of both the deposits and their host craters. Using MOLA topography data, MOC and THEMIS imagery, and SHARAD radar sounding data, we characterize the distribution, morphology, and structure of the deposits. In addition, we examine the effect of the crater microenvironment on the formation and persistence of these deposits, exploring the relative importance of solar and eolian processes in shaping their present-day distribution and appearance. We consider the possibility that crater sand dunes may have promoted ice accumulation over time and weigh various explanations for the origins and larger climatic significance of these features.
by Own William Westbrook.
S.M.
20
Achilles, C. N., R. T. Downs, D. W. Ming, E. B. Rampe, R. V. Morris, A. H. Treiman, S. M. Morrison, et al. "Mineralogy of an active eolian sediment from the Namib dune, Gale crater, Mars." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626447.
Full textAbstract:
The Mars Science Laboratory rover, Curiosity, is using a comprehensive scientific payload to explore rocks and soils in Gale crater, Mars. Recent investigations of the Bagnold Dune Field provided the first in situ assessment of an active dune on Mars. The Chemistry and Mineralogy (CheMin) X-ray diffraction instrument on Curiosity performed quantitative mineralogical analyses of the <150m size fraction of the Namib dune at a location called Gobabeb. Gobabeb is dominated by basaltic minerals. Plagioclase, Fo56 olivine, and two Ca-Mg-Fe pyroxenes account for the majority of crystalline phases along with minor magnetite, quartz, hematite, and anhydrite. In addition to the crystalline phases, a minimum similar to 42wt % of the Gobabeb sample is X-ray amorphous. Mineralogical analysis of the Gobabeb data set provides insights into the origin(s) and geologic history of the dune material and offers an important opportunity for ground truth of orbital observations. CheMin's analysis of the mineralogy and phase chemistry of modern and ancient Gale crater dune fields, together with other measurements by Curiosity's science payload, provides new insights into present and past eolian processes on Mars.
21
Russell, Patrick S. "On the activity of water on Mars : investigations into the groundwater system and the stability of ice in the crater-interior environment /." View online version; access limited to Brown University users, 2005. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3174667.
Full textAbstract:
Thesis (Ph.D.)--Brown University, 2005.Vita. Thesis advisor: James W. Head III. Includes bibliographical references (leaves 43-49, 86-87, 125-130, 191-194, 237-238, 276-277). Also available online.
22
Horvath, David G., and Jeffrey C. Andrews-Hanna. "Reconstructing the past climate at Gale crater, Mars, from hydrological modeling of late-stage lakes." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/625822.
Full textAbstract:
The sedimentary deposits in Gale crater may preserve one of the best records of the early Martian climate during the Late Noachian and Early Hesperian. Surface and orbital observations support the presence of two periods of lake stability in Gale craterprior to the formation of the sedimentary mound during the Late Noachian and after the formation and erosion of the mound to its present state in the Early Hesperian. Here we use hydrological models and late-stage lake levels at Gale, to reconstruct the climate of Mars after mound formation and erosion to its present state. Using Earth analog climates, we show that the late-stage lakes require wetter interludes characterized by semiarid climates after the transition to arid conditions in the Hesperian. These climates are much wetter than is thought to characterize much of the Hesperian and are more similar to estimates of the Late Noachian climate.
23
Clark, Madeline E. "Investigation of the depth and diameter of simple craters in the lunar mare." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/114351.
Full textAbstract:
Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (page 33).
Using altimetry data from the Lunar Orbiter Laser Altimeter (LOLA), the depths and diameters of 1429 simple craters in six different lunar maria units were measured, The analysis utilized a Graphical User Interface that was developed to access the LOLA data base and measure crater depth and diameter.The craters were compared to a published trend of depth/diameter relationships for fresh craters by Pike. By and large, the measured craters were shallower than the fresh crater trend. The pattern of shallowing did not correlate with the age of maria units, indicating a complex pattern of basin degradation.
by Madeline E. Clark.
S.B.
24
L'Haridon, Jonas. "Diagenetic processes on Mars : analysis by the ChemCam instrument on the Curiosity rover." Thesis, Nantes, 2018. http://www.theses.fr/2018NANT4087/document.
Full textAbstract:
L’exploration de la surface de Mars par le rover Curiosity, au niveau du cratère Gale, a permis de révéler la présence de conditions habitables par le passe, a travers l’observation de dépôts sédimentaires fluvio-lacustres attestant d'une activité hydrologique prolongée. Ces roches portent également les stigmates de l’évolution complexe des sédiments lors de la diagenèse, sous forme de veines, nodules et concrétions s'etant formes par la circulation de fluides en sub-surface. A bord du rover, la spectroscopie de plasma induit par laser (LIBS) de l’instrument ChemCam permet une mesure chimique a petite échelle, particulièrement adaptée a l'analyse de tels éléments géologiques. Cette étude démontre que les veines de Ca-sulfate, observées dans toutes les unités géologiques traversées par le rover, présentent des enrichissements ponctuels en Fe témoignant de conditions de formation oxydantes lors de la diagenèse tardive. Par ailleurs, l’une des structures sédimentaires du cratère est caractérisée par des signatures spectrales d’hématite depuis l'orbite, suggérant que sa formation est en partie liée a des processus d'oxydo-reduction, pendant et/ou après le dépôt des sédiments. A cet endroit, ChemCam a mis en évidence la mobilité du Fe lors de la diagenèse, ainsi que la formation d'oxyde de Fe en association avec les veines de Ca-sulfate. Pour conclure, ces travaux montrent l'importance des interactions fluides-roches, comme les réactions d’oxydoreduction, lors de l’enfouissement des sédiments martiens, processus devant être pris en compte pour éviter des erreurs d’interprétation sur l’environnement de dépôt et l’intérêt exo-biologique des sédiments étudiésThe exploration of the Martian surface by the rover Curiosity, at Gale crater, has unveiled past habitable conditions on the planet with evidences for sustained period of surface aqueous activity recorded in fluvio-lacustrine sedimentary deposits. In addition, the rocks also bear traces of the complex post-depositional evolution of the sediments during diagenesis, in the form of small-scale fracture-fills, nodules, and concretions that formed by sub-surface fluid circulations. On board, the rover, the Laser-Induced Breakdown Spectroscopy (LIBS) performed by the ChemCam instrument provide remote fine-scale chemical measurements, especially suited to the analysis of such geological items. This study demonstrates that the Ca-sulfate-bearing veins, observed across all geological terrains, show enrichments in Fe at specific locations along the rover traverse, tracing localized oxidizing conditions at the time of their formation in the later stages of diagenesis. Additionally, a key sedimentary structure in Gale crater is characterized by hematite spectral signatures from orbit, suggesting the involvement of redox-driven processes in its formation, either related to primary deposition or post-depositional conditions. There, in situ ChemCam observations highlight the mobility of Fe during diagenesis and the authigenic formation of Fe-oxide in association with Ca-sulfate bearing features. As such, this work attests of significant fluid interactions, and notably redox-driven chemical reactions, affecting the Martian sediments after their deposition and burial, which need to be taken into account in order to avoid any misinterpretations on the environment of deposition and its habitability
25
Hsu, Hsin-Jen. "Investigation of the relationship of crater depths and diameters in selected regions of Mars." Thesis, Northern Arizona University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1537780.
Full textAbstract:
Impact craters are common geomorphological features on Mars. The density of craters is different among various regions. Higher crater density means older terrain. Craters can be divided into two types by the interior morphology: simple and complex. The cavity of Simple craters is bowl-shape, and complex craters display various interior features, such as central peaks. The depth/diameter ratio (d/D) of simple craters is larger than that of complex craters. The transition diameter from simple to complex morphologies ranges between 5 and 10 km, and is commonly cited to be about 7 km in the equatorial regions and 6 km near the poles, but the exact value also could vary with terrain type. In this research, seven regions, Amazonis Planitia, Arabia Terra, Chryse Planitia, Hesperia Planum, Isidis Planitia, Solis/Syria/Sinai Planum, and Terra Sirenum, were selected to investigate the onset diameter of complex craters and the relationship of crater diameter and depth in these regions on Mars in order to understand how the geology affects crater d/D. The analysis revealed that the slopes of the d/D relations are different, and these are linked to the surface material in different regions. The onset diameters in young volcanic regions with stronger material are slightly higher than older volcanic regions, and much higher than that of volatile regions. The research proves the different geological units can affect the morphology and morphometry of craters.
26
Kolb, Kelly Jean. "Modeling Bright Gully Deposits' Formation in Hale Crater, Mars: Implications for Recent Liquid Water." Thesis, The University of Arizona, 2008. http://hdl.handle.net/10150/193349.
Full textAbstract:
This study aims at uncovering the formation mechanism of the recent bright gully deposits observed on Mars in order to assess the viability of liquid water involvement. I use a high resolution topography model as input into a kinematic model to assess whether or not a dry granular flow could form the bright gully deposits seen in Hale Crater. I investigate a dry mechanism due to the difficulty of producing water on the martian surface under present-day pressure and temperature conditions. I examine a range of particle sizes, flow thicknesses, and upslope initiation points to examine how these parameters affect the run-out distances of flows. The results show that multiple combinations of parameters could produce flows that travel to within the observed deposits' boundaries. The results suggest that the recent bright gully deposits are not evidence of recent liquid water on the surface of Mars.
27
Christoff, Vesselinova Nicole. "Détection et caractérisation d'attributs géométriques sur les corps rocheux du système solaire." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0565/document.
Full textAbstract:
L’un des défis de la science planétaire est la détermination de l’âge des surfaces des différents corps célestes du système solaire, pour comprendre leurs processus de formation et d’évolution. Une approche repose sur l’analyse de la densité et de la taille des cratères d’impact. En raison de l’énorme quantité de données à traiter, des approches automatiques ont été proposées pour détecter les cratères d’impact afin de faciliter ce processus de datation. Ils utilisent généralement les valeurs de couleur des images ou les valeurs d’altitude de "modèles numériques d’élévation" (DEM). Dans cette thèse, nous proposons une nouvelle approche pour détecter les bords des cratères. L’idée principale est de combiner l’analyse de la courbure avec une classification basée sur un réseau de neurones. Cette approche comporte deux étapes principales : premièrement, chaque sommet du maillage est étiqueté avec la valeur de la courbure minimale; deuxièmement, cette carte de courbure est injectée dans un réseau de neurones pour détecter automatiquement les formes d’intérêt. Les résultats montrent que la détection des formes est plus efficace en utilisant une carte en deux dimensions s’appuyant sur le calcul d’estimateurs différentiels discrets, plutôt qu’en utilisant la valeur de l’élévation en chaque sommet. Cette approche réduit significativement le nombre de faux négatifs par rapport aux approches précédentes basées uniquement sur une information topographique. La validation de la méthode est effectuée sur des DEM de Mars, acquis par un altimètre laser à bord de la sonde spatiale "Mars Global Surveyor" de la NASA et combinés avec une base de données de cratères identifiés manuellementOne of the challenges of planetary science is the age determination of the surfaces of the different celestial bodies in the solar system, to understand their formation and evolution processes. An approach relies on the analysis of the crater impact density and size. Due to the huge quantity of data to process, automatic approaches have been proposed for automatically detecting impact craters in order to facilitate this dating process. They generally use the color values from images or the elevation values from Digital Elevation Model (DEM). In this PhD thesis, we propose a new approach for detecting craters rims. The main idea is to combine curvature analysis with Neural Network based classification. This approach contains two main steps: first, each vertex of the mesh is labeled with the value of the minimal curvature; second, this curvature map is injected into a neural network to automatically detect the shapes of interest. The results show that detecting forms are more efficient using a two-dimensional map based on the computation of discrete differential estimators, than by the value of the elevation at each vertex. This approach significantly reduces the number of false negatives compared to previous approaches based on topographic information only. The validation of the method is performed on DEMs of Mars, acquired by a laser altimeter aboard NASA’s Mars Global Surveyor spacecraft and combined with a database of manually identified craters
28
Monders, Anna Gabrielle Bogan. "Phase equilibrium investigations of the Adirondack Class basalts from the Gusev plains, Gusev crater, Mars." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37281.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2006.Includes bibliographical references (leaves 48-51).
Phase equilibrium experiments have been performed on a synthetic analog of the Gusev plains basalt composition from the Spirit landing site on Mars, determined by the Alpha Particle X-ray Spectrometer on the Spirit Rover (Gellert et al., 2006; McSween et al., 2006). The near-liquidus phase relations were determined over the pressure range of 0.1 MPa to 1.5 GPa and at temperatures from 1105 °C to 1390 °C in a piston cylinder apparatus and l-atm gas mixing furnace. The composition is multiply saturated with olivine, orthopyroxene, and spinel on the liquidus at 1310 °C and 1.0 GPa, or 85 km depth on Mars, placing an upper limit constraint on the thickness of the Martian lithosphere at the time of eruption. Experiments carried out at 0.1 MPa show Fo77 olivine as the first liquidus silicate mineral, appearing near 1250 °C. Olivine and spinel co-crystallize until pigeonite and plagioclase (An73) join the crystallizing assemblage at 1125 °C. Low pressure crystallization of the Gusev composition does not produce liquids that could be parental magmas to surface types 1 and 2 of the Martian surface, nor do they appear to be related to olivine-phyric shergottites or other SNC meteorites. The iron-rich Gusev basalts appear to have been crystallized from a less depleted mantle source than the magnesian olivine-phyric shergottite Yamoto 980459.
by Anna Gabrielle Bogan Monders.
S.M.
29
Sara, Michael James. "Dyngjusandur sand sheet, Iceland, as a depositional analog to the Stimson Fm. in Gale Crater, Mars." Thesis, University of Iowa, 2017. https://ir.uiowa.edu/etd/5621.
Full textAbstract:
Basalts from Askja, Iceland have high MgO (5-18 wt %) and high Fe2O3 (5-18 wt %: Baratoux et al., 2011; Mangold et al., 2013, this study) similar to Martian basalts, which have Fe2O3 from 10-33 wt % McSween et al, 2006; Ming et al., 2008]) and MgO around 11 wt. % (McSween et al., 2009). Askja’s cold desert climate provides a good weathering analogueanalog (Mountney and Russell, 2004). Askja is located in the Northern Volcanic Zone of Iceland and basalts have been weathered to form mafic volcaniclastic deposits in a 40-km long sand sheet to the E-SE of the Askja caldera complex (Fig. 1; (Kuritani et al., 2011). The 2014-2015 Holuhraun eruption was emplaced onto the southeastern part of the sand sheet (Fig. 1) and altered the regional geomorphology and may have impacted the geochemistry of the sand sheet itself by addition of wind-blown ash and crystals, plus weathering of the lava flow (MgO content of ~7.1 wt % Geiger et al., 2016). Mangold et al. (2011) found that Icelandic sands show little chemical variations but that study was limited in the number of samples (12 sand samples and 12 rock seven rock, seven sand; Mangold et al., 2011). Here we expand on that study and we have created a morphological and geochemical database with the goal of identifying relevant trends to past and present Martian environments.
The Askja sand sheet, between ~10 cm and ~10 m thick, covers 240 km2 (Mountney and Russell). Mountney and Russell described three distinct sections of the sand sheet. The southwest section is deflationary and defined by very fine to medium grained basaltic sand with cobbles and boulders of lithologies sourced from adjacent to and distal from the sand sheet. The central part is inflating and is dominated by very fine-grained sand, relict lava fields, and small to large sand ripples. The northeast portion is also inflating but that accumulation is limited to topographic depressions. The northeast, characterized by sand mostly composed of pumice from the 1875 Askja eruption and basalt clasts from local lava fields, was not studied in detail here due to the difference in chemistry. Martian basaltic eolian sediments may record a long history of local and global climate change and they may have been potential habitats where water, nutrients and organic carbon mixed below the surface (Blake et al., 2013; Fisk et al., 2013). Basaltic sand fields on Earth have not been characterized as well as felsic sands, but represent a unique analog to deposits such as the Stimson Fm. on Mars (Mangold et al., 2011; Banham et al., 2016; Gupta et al., 2016; Ming et al., 2016; Newsom et al., 2016; Yen et al., 2016) . Eolian dominated weathering prevalent at Askja volcano, Iceland, likely also occurred on Mars and Askja mafic volcaniclastic dunes could be the best morphological and compositional analogueanalog for Martian eolian dunes (Edgett and Lancaster, 1993).
30
Elwood, Madden Megan Erica. "Fluids in Planetary Systems." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/28034.
Full textAbstract:
From the early stages of planetary accretion and differentiation to the geomorphology of planetary surfaces and the evolution of life, fluids play an integral role in shaping planetary bodies. Fluid properties and processes were investigated under a range of planetary conditions through (1) experimental simulations of impact events and petrographic analysis of terrestrial impactites to determine the effects of shock metamorphism on fluid inclusion properties; and (2) numerical thermodynamic equilibrium modeling of aqueous alteration processes on Mars.
Results of impact experiments and analyses of fluid inclusions in rocks from the Ries Crater and Meteor Crater indicate that fluid inclusions reequilibrate systematically with increasing shock pressure: stretching and decrepitating under low shock pressure conditions and collapsing at moderate shock pressures. Above the Hugenoit Elastic Limit, fluid inclusion vesicles are destroyed due to plastic deformation and phase transitions within the host mineral. This suggests that impact processing may result in the destruction of fluid inclusions, leading to shock devolatilization of target rocks. In addition, the absence of fluid inclusions in planetary materials does not preclude the presence of fluids on the meteoriteâ s parent body.
Thermodynamic modeling of aqueous alteration of basalt under Mars-relevant conditions provides constraints on the conditions under which secondary sulfates are likely to have formed. The results of this study indicate that jarosite is likely to form as a result of water-limited chemical weathering of basalts. Magnesium sulfates are only predicted to form as a result of evaporation. This suggests that in order to form the alteration assemblages recently observed by the Mars Exploration Rover Opportunity at Meridiani Planum, water must have been removed from the system after a geologically short period of time, before fluids came into equilibrium with mafic surface materials and became alkaline.Ph. D.
31
Johnson, Jeffrey R., Cherie Achilles, James F. Bell, Steve Bender, Edward Cloutis, Bethany Ehlmann, Abigail Fraeman, et al. "Visible/near-infrared spectral diversity from in situ observations of the Bagnold Dune Field sands in Gale Crater, Mars." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626566.
Full textAbstract:
As part of the Bagnold Dune campaign conducted by Mars Science Laboratory rover Curiosity, visible/near-infrared reflectance spectra of dune sands were acquired using Mast Camera (Mastcam) multispectral imaging (445-1013nm) and Chemistry and Camera (ChemCam) passive point spectroscopy (400-840nm). By comparing spectra from pristine and rover-disturbed ripple crests and troughs within the dune field, and through analysis of sieved grain size fractions, constraints on mineral segregation from grain sorting could be determined. In general, the dune areas exhibited low relative reflectance, a weak similar to 530nm absorption band, an absorption band near 620nm, and a spectral downturn after similar to 685nm consistent with olivine-bearing sands. The finest grain size fractions occurred within ripple troughs and in the subsurface and typically exhibited the strongest similar to 530nm bands, highest relative reflectances, and weakest red/near-infrared ratios, consistent with a combination of crystalline and amorphous ferric materials. Coarser-grained samples were the darkest and bluest and exhibited weaker similar to 530nm bands, lower relative reflectances, and stronger downturns in the near-infrared, consistent with greater proportions of mafic minerals such as olivine and pyroxene. These grains were typically segregated along ripple crests and among the upper surfaces of grain flows in disturbed sands. Sieved dune sands exhibited progressive decreases in reflectance with increasing grain size, as observed in laboratory spectra of olivine size separates. The continuum of spectral features observed between the coarse- and fine-grained dune sands suggests that mafic grains, ferric materials, and air fall dust mix in variable proportions depending on aeolian activity and grain sorting.
32
Payré, Valérie. "Contribution de l’instrument ChemCam à la compréhension de la croûte primitive martienne et des mécanismes d’altération de la surface de Mars : quantification LIBS des éléments traces Li, Rb, Sr, Ba et Cu." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0264/document.
Full textAbstract:
Jusqu’à peu, Mars était vue comme une planète à substrat crustal homogène, dominé par des basaltes à olivine. Les missions in situ ont contribué à bouleverser cette vision si simpliste. Le rover Curiosity qui sillonne le cratère d’impact de Gale formé à l’Hespérien (3.5-3.8 Ga) creusé dans des roches noachiennes (> 3.8 Ga), a ainsi découvert, grâce aux analyses LIBS (‘laser induced breakdown spectroscopy’) de l’instrument ChemCam, des roches ignées alcalines felsiques noachiennes, révélant un magmatisme primitif évolué (Sautter et al., 2016) : ce résultat est en accord avec l’identification récente de clastes ignés felsiques d’âge Noachien observés dans la brèche martienne NWA 7533 et ses paires. Une croûte primitive martienne évoluée de type ‘continentale’ aurait-elle existé ? C’est ce que suggère ce travail de par l’observation orbitale GRS de plusieurs terrains noachiens felsiques enrichis en K et Th et abondants en feldspaths. Par ailleurs, du fait de l’identification de feldspaths peu calciques dans les roches et clastes de Gale et de la brèche, il est envisagé ici que la croûte primitive martienne ait pu se former selon un modèle différent de l’océan de magma défini sur la Lune. De plus, la quantification de Li, Rb, Sr et Ba dans l’ensemble des matériaux ignés de Gale analysés par la LIBS ainsi que leurs concentrations dans les clastes ignés de la brèche, suggèrent l’existence de plusieurs réservoirs magmatiques primitifs. En parallèle, la quantification du Cu à partir des données LIBS effectuée dans cette étude, met en évidence des abondances anormalement élevées dans des roches potassiques de la région de Kimberley. Majoritairement associées à des silicates détritiques ignés, ces phases de cuivre proviendraient d’une source magmatique primitive siliceuse localisée dans le flanc Nord de Gale. Au Noachien, la circulation hydrothermale dans un magma évolué aurait formé un gisement métallifère de cuivre aux alentours du cratère. Finalement, la Terre et Mars sont géologiquement plus proches que jamaisUntil recently, Mars was considered as a planet with a homogeneous crust dominated by olivine-rich basalts. This simplistic vision has been largely disrupted especially with results of recent in situ missions. In this way, the Curiosity rover that travels in Gale crater, which formed by impact during the Hesperian period (3.5-3.8 Gyr) within igneous basement rocks dated at 4.2 Gyr, discovered Noachian alkaline igneous rocks (> 3.8 Gyr) using the ChemCam LIBS instrument (‘laser induced breakdown spectroscopy’): this observation along with the recent identification of Noachian igneous felsic clasts within the breccia meteorite NWA 7533 and subsequent paired stones, revealed an evolved primitive magmatic system (Sautter et al., 2016). Would an evolved ‘continental’ primitive crust have ever existed on Mars? This is favored in this work by orbital GRS observations showing several Si-K-Th-rich Noachian terrains displaying abundant feldspars. Besides, the identification of low-Ca feldspars within the clasts of the breccia and Gale rocks, suggests that the primitive martian crust may have formed according to a model that differs from the lunar magma ocean. In addition, the LIBS quantification of Li, Rb, Sr and Ba presented in this work in igneous rocks, along with the distribution of alkali trace elements within the igneous clasts of the breccia, suggests the potential occurrence of several magmatic reservoirs. Concurrently, in the Kimberley formation, copper quantification using LIBS data, reveals anomalously elevated abundances within potassic rocks: these Cu-phases mainly associated with detrital igneous silicates, would come from a primitive felsic igneous source located in the northern rim. During the Noachian period, the hydrothermal circulation within an evolved magmatic chamber favored the formation of a Cu-bearing deposit in Gale vicinity. After all, the Earth and Mars are geologically closer than ever
33
Rapin, William. "Hydratation de la surface de Mars à partir des données du rover Curiosity." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30338.
Full textAbstract:
La recherche des phases hydratées à la surface de Mars est essentielle à la compréhension de son passé habitable et des changements climatiques globaux qu'elle a subis. Le rover MSL/Curiosity apporte de nouveaux moyens pour caractériser l'hydratation de la surface. En particulier, la spectroscopie de plasma induite par laser (LIBS) de l'instrument ChemCam mesure la composition élémentaire à distance. Il permet une détection de l'hydrogène par le pic d'émission H Balmer alpha à 656.6 nm. Cependant la quantification de cet élément n'a été que très peu étudiée. Le modèle de qualification de l'instrument ChemCam a été intégré à un banc LIBS afin d'analyser des séries d'échantillons hydratés au laboratoire. A l'exception de quelques échantillons révélant des phénomènes spécifiques à l'hydrogène, ces tests montrent qu'un étalonnage linéaire est obtenu avec la teneur en eau. Sur Mars, dans le cratère Gale, cette calibration révèle l'hydratation de différentes phases : la bassanite (CaSO4 × 0.5H2O) dans les veines remplissant les fractures des roches, les sulfates de magnésium, les sédiments opalifères et argileux découverts in situ. Les mesures d'abondances en eau effectuées jusqu'à présent étaient restreintes à de rares expériences de pyrolyse ; cette étude montre que ChemCam apporte maintenant un nouveau moyen opérationnel pour la mesure de l'hydrogène à la surface, à l'échelle submillimétrique et couvrant un très grand nombre de rochesThe search for hydrated phases lying at the surface of Mars is essential to understand its habitable past and the fate of water on a planet disrupted by global climate changes. The MSL/Curiosity rover provides new tools to characterize surface hydration in situ. Among these, laser induced breakdown spectroscopy (LIBS) performed by the ChemCam instrument enables remote measurement of elementary abundance. However, measuring the LIBS emission peak of hydrogen at 656.6 nm (Balmer alpha) to quantify target water content is poorly documented in the literature. Using the instrument replica, large series of hydrated samples have been analyzed in the laboratory under Martian atmospheric conditions. Except for some samples on which effects specific to the hydrogen signal have been observed, these tests show that a linear calibration can be obtained with target water content. On Mars, at Gale crater, this calibration reveals the hydration of different phases: bassanite (CaSO4 × 0.5H2O) in the veins filling the bedrock fractures, magnesium sulfates, opaline and clay rich sediments discovered in situ. Measurement of water content performed to date have been limited to sparse and bulk pyrolysis experiments; this study shows that ChemCam provides a new technique to measurement hydrogen on the surface, at a submillimeter scale and sampling a very large number of rocks
34
Ehlmann, B. L., K. S. Edgett, B. Sutter, C. N. Achilles, M. L. Litvak, M. G. A. Lapotre, R. Sullivan, et al. "Chemistry, mineralogy, and grain properties at Namib and High dunes, Bagnold dune field, Gale crater, Mars: A synthesis of Curiosity rover observations." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626565.
Full textAbstract:
The Mars Science Laboratory Curiosity rover performed coordinated measurements to examine the textures and compositions of aeolian sands in the active Bagnold dune field. The Bagnold sands are rounded to subrounded, very fine to medium sized (similar to 45-500m) with 6 distinct grain colors. In contrast to sands examined by Curiosity in a dust-covered, inactive bedform called Rocknest and soils at other landing sites, Bagnold sands are darker, less red, better sorted, have fewer silt-sized or smaller grains, and show no evidence for cohesion. Nevertheless, Bagnold mineralogy and Rocknest mineralogy are similar with plagioclase, olivine, and pyroxenes in similar proportions comprising >90% of crystalline phases, along with a substantial amorphous component (35%15%). Yet Bagnold and Rocknest bulk chemistry differ. Bagnold sands are Si enriched relative to other soils at Gale crater, and H2O, S, and Cl are lower relative to all previously measured Martian soils and most Gale crater rocks. Mg, Ni, Fe, and Mn are enriched in the coarse-sieved fraction of Bagnold sands, corroborated by visible/near-infrared spectra that suggest enrichment of olivine. Collectively, patterns in major element chemistry and volatile release data indicate two distinctive volatile reservoirs in Martian soils: (1) amorphous components in the sand-sized fraction (represented by Bagnold) that are Si-enriched, hydroxylated alteration products and/or H2O- or OH-bearing impact or volcanic glasses and (2) amorphous components in the fine fraction (<40m; represented by Rocknest and other bright soils) that are Fe, S, and Cl enriched with low Si and adsorbed and structural H2O. Plain Language Summary The Bagnold dune field is an active sand field with moving dunes and sits between the landing site of the Curiosity rover and rocks of interest higher up on Mount Sharp. When passing through the dune field, we used all of Curiosity's instruments to measure the chemistry, mineralogy, and grain size of sands in the Bagnold dune field in order to figure out where they came from, how the sands are transported, and what volatile materials (like water) lie within Martian soils. We found that the Bagnold sand dunes are very well sorted; no dusty materials are found within them, in stark contrast to soils seen previously with Curiosity and with rovers at other landing sites. We found that the coarser sand grains are enriched in the volcanic minerals olivine and pyroxene, confirming a prediction from orbit that wind-related activity seems to concentrate these phases. We also found that the dunes were much lower in water and other volatile elements like sulfur and chlorine versus all previous Mars soils. Using a combination of the rover's sieving system and chemical measurement tools, we figured out that two types of materials host water. In the first type of material, common in these sands, water is low in abundance (similar to 1%), very tightly bound to the grains, and is not released until temperatures >200 degrees C. In the second type of material, water is higher in abundance (2%) and more easily released by heating. Sieved water-bearing fine materials may be a useful resource for human explorers.
35
Larson, Susan K. "The Origins of Four Paterae of Malea Planum, Mars." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1736.pdf.
Full text
36
Thomas, Pierre. "Étude géologique des vieilles surfaces planétaires : Mercure, Lune, hémisphère sud de Mars, Ganymède, Callisto et Rhéa." Paris 11, 1986. http://www.theses.fr/1986PA112080.
Full textAbstract:
Cette thèse présente les résultats d’études géologiques concernant six planètes dont l’activité géologique a cessé il y a plus de trois milliards d’années. Il s’agit aussi bien de planètes telluriques (Mercure, Lune Mars) que de satellites de glace (Ganymède, Callisto, Rhéa). La méthode de travail employée a été la suivante : collecte de données nouvelles par l’analyse photogéologique détaillée des images transmises par les ondes américaines, puis élaboration de modèles qualitatifs ou quantitatifs pour expliquer ces données. Il a été ainsi possible de proposer un scénario concernant l’histoire géologique de ces six planètes, et surtout de préciser l’importance réelle des grand agents géologiques ayant façonnée leur surface ; la tectonique d’origine interne (convection…) est presque totalement absente de ces planètes qui n’ont disposé que d’une très faible quantité d’énergie (sauf Mars). Le volcanisme (silicaté ou hydroammoniaqué) est abondant sur la Lune, Ganymède et Rhéa où il représente la seule manifestation significative de l’énergie interne. Sur Mercure et Callisto, ce volcanisme est très limité et uniquement dû à des évènements locaux (décompression suivant un impact). Des accidents tectoniques présents sur toute la surface de ces planètes attestent de variations de volume (dues à des variations de température interne en ou à des changements de phases de la glace) et de forme (dues à des perturbations orbitales)This thesis describes the geological histories of six planetary bodies with low internal activity: three terrestrial planets (Moon Mercury, and the south hemisphere of Mars) and three icy satellites (Ganymede, Callisto, and Rhea). The data were collected from the pictures of american spacecrafts and were furthermore used to propose qualitative or quantitative models explaining the data. Thus, it was possible to propose a scenario concerning the histories of these six planetary bodies, and to appreciate the real influence of each geological process which affects the planetary surface and interior. The tectonic induced by internal motions and convections occurred only on Mars. The widely present volcanism due to interior melting has existed on the Moon, Mars (silicated volcanism), Ganymede and Rhea (NH3/H20 volcanism). On the contrary, Mercury and Callisto only exhibit little volcanism due to local events (Calorie and Valhalla). The radius or shape variations due to thermal or orbital perturbations induced widespread planetary grids on these six bodies. The large impact craters considerably influenced the local and global tectonics, when they were deeper than the lithospheric thickness (Mars, Ganymede, Callisto), or when their size was important in regard of planetary radius (Mercury, Moon).
37
Baratoux, David. "Topographie martienne haute-résolution et dynamique des cratères d'impact à Ejecta Lobès : conséquences sur la distribution de l'eau sur Mars." Université Joseph Fourier (Grenoble), 2001. http://www.theses.fr/2001GRE10145.
Full textAbstract:
La connaissance de la topographie Martienne est indispensable à la quantification des processus géologiques et à la compréhension de ces phénomènes. Une méthodologie de restitution à haute résolution de la topographie à partir d'images Viking a été développée selon trois étapes originales : corrélation des images Viking effectuée dans l'espace de Fourier, ajustement des caméras par orientation relative et orientation absolue puis validation à l'aide données d'altimétrie laser MOLA. La topographie ainsi obtenue sur une avalanche de débris récente démontre le rôle de l'eau liquide dans le mécanisme d'écoulement. La technique, transférée aux images aériennes terrestres, est appliquée au suivi temporel du glissement de terrain de la Clapière, St-Etienne de Tinée. Les morphologies des cratères d'impact à éjecta lobés dépendent de la concentration en glace dans le sous-sol. Une étude des paramètres physiques contrôlant la formation des cratères d'impact est réalisée afin d'interpréter la géométrie des dépôts d'éjecta. La mesure de la mobilité des éjecta définie par le rapport entre leur extension maximale et le rayon du cratère est appliquée à la cartographie de la profondeur du toit du pergélisol. Un mécanisme d'instabilité gravitationnelle, observé expérimentalement dans les écoulements visqueux, est proposé pour expliquer le contour sinueux des éjecta. Ce modèle relie les longueurs d'onde des lobes à la viscisité du mélange liquide-particules solides dépendant de la concentration en eau. L'analyse des longueurs d'onde de 1000 cratères lobés a permis de quantifier les variations relatives de la viscosité des éjecta en fonction de leurs profondeurs reliées aux diamètres des cratères. La diminution de la concentration en glace avec la profondeur estimée par ce modèle est cohérente avec la diminution de la porosité dans le régolite.
38
Daket, Yuko. "Copernican and Eratosthenian tectonics in the northwestern Imbrium region of the Moon revealed by conventional remote sensing techniques and newly developed one-dimensional crater chronology." Doctoral thesis, Kyoto University, 2017. http://hdl.handle.net/2433/226756.
Full textAbstract:
京都大学0048
新制・課程博士
博士(理学)
甲第20602号
理博第4317号
新制||理||1620(附属図書館)
京都大学大学院理学研究科地球惑星科学専攻
(主査)教授 山路 敦, 教授 山 明, 准教授 伊藤 正一
学位規則第4条第1項該当
Doctor of Science
Kyoto University
DGAM
39
Daket, Yuko, and Yuko Dake. "Copernican and Eratosthenian tectonics in the northwestern Imbrium region of the Moon revealed by conventional remote sensing techniques and newly developed one-dimensional crater chronology." Kyoto University, 2007. http://hdl.handle.net/2433/226756.
Full text
40
Degeai, Jean-Philippe. "Mesure de l'érosion à différentes échelles spatio-temporelle autour des maars et des astroblèmes : exemples dans le Massif Central français et le Québec." Paris 4, 2005. http://www.theses.fr/2005PA040169.
Full textAbstract:
Trois nouvelles méthodes de calcul ont été élaborées afin de mesurer l'érosion à différentes échelles spatio-temporelles dans le Massif central français et le Québec. Ces méthodes s'appuient sur l'analyse de la morphologie de structures monogéniques bien datées : les maars et les astroblèmes. Elles permettent de déterminer : 1) l'épaisseur de substrat érodé autour des astroblèmes, 2) le niveau de déchaussement des systèmes maars-diatrèmes en inversion de relief, 3) l'épaisseur moyenne de la tranche de roche érodée à la surface du bassin versant d'un maar, d'après le volume de sédiments contenus dans le cratère. En général, les taux moyens d'érosion autour des astroblèmes sont inférieurs à 5 mm. Ka-1 depuis la fin du Paléozoïque ou le début du Mésozoïque. La vitesse de l'érosion à long terme et à court terme autour des maars néogènes et quaternaires du Massif central est le plus souvent comprise entre 10 et 50 mm. Ka-1. Les résultats obtenus sont ensuite utilisés dans des applications géomorphologiques traitant de l'analyse des rythmes morphogéniques dans les socles et leurs couvertures sédimentaires et/ou volcaniques, selon trois thématiques : 1) les vitesses moyennes d'élaboration des surfaces d'aplanissement phanérozoïques autour des grands astroblèmes et des diatrèmes du Québec, 2) l'évolution des rythmes de l'érosion post-oligocène de deux secteurs situés dans l'est du Massif central (sud de la plaine de Limagne et Coirons orientaux), 3) les facteurs de variation des taux d'érosion à plus court terme dans les bassins versants de plusieurs maars quaternaires d'Auvergne et du VelayThree new calculation methods have been developed in order to measure the erosion at various scales of space and time in the French Massif Central and Quebec. These methods are based upon the morphological analysis of well-dated monogenic structures represented by maars and astroblemes. The calculations yield evaluations of: (1) the thickness of eroded bedrock in the surrounds of astroblemes, (2) the value of the erosion around the topographically inverted maar-diatreme systems, (3) the mean thickness of the eroded rock slice in the catchment area of a maar, from the bulk of sediments filling the crater. The mean erosion rates around the astroblemes are generally lower than 5 mm. Ky-1. The long-term and short-term erosion rates around the Neogene and Quaternary maars of the French Massif Central usually range between 10 and 50 mm. Ky-1. The results obtained by the calculation methods are then used in geomorphic applications, in order to analyse the morphogenical rhythms in basement terrains and their sedimentary and/or volcanic covers, at three time scales: (1) the long-term erosion mean rates of the Phanerozoic planation surfaces around the great astroblemes and diatremes of Quebec, (2) the evolution of the Late Cenozoic erosional rhythms in two areas of the eastern part of the French Massif Central (southern plain of the Limagne and eastern Coirons), (3) the origins of variations of short-term erosion rates inside the catchment areas of several Quaternary maars in the Auvergne and Velay
41
Ouattara, Yacouba. "Structure sismique de l'Afrique de l'Ouest par tomographie d'ondes de surface." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAH006/document.
Full textAbstract:
Cette thèse nous a permis de produire des cartes de vitesse de groupe du mode fondamental des ondes de Rayleigh, en utilisant les séismes et les corrélations du bruit sismique ambiant. En plus de la méthode moindres carrées amortis, nous avons adapté la nouvelle méthode d’inversion, SOLA-Backus-Gilbert dans un contexte régional. À courte période, les cartes de vitesse de groupe présentent des vitesses rapides pour la croûte océanique et des vitesses lentes pour la croûte continentale. Pour les périodes intermédiaires, le bassin de Taoudeni se caractérise par de faibles vitesses par rapport au reste du craton ouest africain en raison de l’épaisseur de la couche sédimentaire. A longue périodes, les racines des dorsales Man-Leo et Reguibat sont caractérisées par des vitesses rapides, montrant une lithosphère froide et épaisse sous le craton, tandis que nous avons trouvé des vitesses de groupe lentes sous les zones de ceinture mobile panafricaine indiquant une lithosphère minceThis thesis allowed us to produce group velocity maps of the fundamental mode of Rayleigh waves, using both earthquakes and seismic ambient noise correlation. In this study, in addition to the damped least squares method, we adapted for the very first time a new inversion method, called SOLA-Backus-Gilbert in regional context. At short periods, the group velocities maps exhibit fast velocities for the oceanic crust and slow velocities for the continental crust. For the intermediate periods, the Taoudeni Basin is characterized by low velocities compared to the rest of the west african craton due to the thickness of the sedimentary layer. Over long periods, the roots of the Man-Leo and Reguibat shields are characterized by fast velocities, showing a cold and thick lithosphere under the craton, while we found slow group velocities under the Pan-African orogenic belts zones indicating a thin lithosphere
42
"Distribution of Windblown Sediment in Small Craters on Mars." Master's thesis, 2011. http://hdl.handle.net/2286/R.I.8923.
Full textAbstract:
abstract: Many shallow craters near the Spirit Mars Exploration Rover landing site contain asymmetric deposits of windblown sediments which could indicate the predominant local wind direction at the time of deposition or redistribution. Wind tunnel simulations and field studies of terrestrial craters were used to determine trends in deposition as a function of crater morphometry and wind direction. Terrestrial analog field work at the Amboy lava field, Mojave Desert, California, included real-time wind measurements and assessments of active sediment deposition in four small (<100 m) craters. Preliminary results indicate that reverse flow or stagnant wind and deposition on the upwind side of the crater floor occurs in craters with depth-to-diameter (d/D) ratios ≥0.05. Measurements taken within a crater of d/D of ~0.02 do not indicate reverse flow. Therefore, reverse flow is expected to cease within a d/D range of 0.02 to 0.05, resulting in wind movement directly over the crater floor in the downwind direction with no asymmetric sediment deposition. Wind tunnel simulations using six crater models, including a scaled model of a crater from the Amboy lava field, were completed to assess the wind flow in and around craters as a function of crater morphometry (depth, diameter). Reverse flow occurred in craters with d/D ratios ≥0.033, resulting in sediment deposition in the upwind portion of the crater floor. Visual observations of a crater with a d/D of ~0.020 did not indicate reverse flow, similar to the results of field studies; therefore, reverse flow appears to cease within a d/D range of 0.020 to 0.033. Craters with asymmetric aeolian deposits near the Mars Spirit landing site have d/D ratios of 0.034 to 0.076, suggesting that reverse flow occurs in these craters. Thus, the position of windblown sediments in the northwest parts of the crater floors would indicate prevailing winds from the northwest to the southeast, consistent with late afternoon winds as predicted by the Mars Regional Atmospheric Modeling System (MRAMS) circulation model.Dissertation/Thesis
M.S. Geological Sciences 2011
43
Schneider, Romy D. "Evidence for locally-derived, ultramafic intracrater materials in Amazonis Planitia, Mars." Thesis, 2006. http://hdl.handle.net/10125/20620.
Full text
44
Adcock, Christopher Terry. "Determining formative winds through geomorphology Herschel Crater, Mars /." 2004. http://digital.library.okstate.edu/etd/umi-okstate-1195.pdf.
Full text
45
"Wind-driven Modification of Small Bedforms in Gusev Crater, Mars." Master's thesis, 2016. http://hdl.handle.net/2286/R.I.40328.
Full textAbstract:
abstract: ABSTRACT
The Spirit landing site in Gusev Crater has been imaged by the Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment (HiRISE) camera more than thirty times since 2006. The breadth of this image set allowed a study of changes to surface features, covering four Mars years.
Small fields of bedforms comprised of dark material, and dark dust devil tracks are among the features revealed in the images. The bedforms are constrained within craters on the plains, and unconstrained in depressions less than 200m wide within the topography of the Columbia Hills, a ~120m-high structure in center of Gusev. Dust devil tracks appear in many images of the bedforms.
Within the Columbia Hills, three bedform fields approximately 180m2 and composed of fine dark basaltic sand were studied, using five HiRISE images taken from 2006 to 2014. Both bedform crests and the dust devil tracks superimposed on them were evaluated for change to azimuth and length, and for correlation between the features. The linear to slightly sinuous transverse crests ranging from less than 1m to 113m in length and two to three meters in wavelength, are primary bedforms. During the study they shifted as much as 33 degrees in azimuth, and individual crests moved on the surface as much as 0.75m. The greatest changes corresponded to a global dust storm in 2007. Average crest movement was documented at the rate of 0.25m per year. Rather than moving progressively, the crests eventually returned to near their original orientation after the storm. The dust devil tracks, reflecting a more complex wind regime, including vortex development during diurnal heating, maintained predominantly NW-SE orientations but also reflected the effects of the storm.
The observed modifications were neither progressive, nor strictly seasonal. The apparent stability of the bedform geometry over four seasons supports the predictions of the Mars Regional Atmospheric Modeling System (MRAMS): low speed (1-7.5 ms-1), daily alternating winds of relatively equal force. Crest profiles were found to be nearly symmetrical, without slipfaces to indicate a preferential wind direction; this finding also is supported by the MRAMS model.Dissertation/Thesis
Masters Thesis Geological Sciences 2016
46
Siebach, Kirsten Leigh. "Formation and Diagenesis of Sedimentary Rocks in Gale Crater, Mars." Thesis, 2016. https://thesis.library.caltech.edu/9838/13/Siebach_Kirsten_Thesis_2016.pdf.
Full textAbstract:
The history of surface processes on Mars is recorded in the sedimentary rock record. Sedimentary rock layers exposed in Gale Crater on the modern crater floor (Aeolus Palus) and on Mount Sharp (Aeolus Mons), which hosts one of the more complete records of transitions between major mineralogical eras on Mars, have been investigated by the Mars Science Laboratory Curiosity rover since landing in August 2012. This dissertation focuses on the formation and diagenesis of the sedimentary rocks in Gale crater in order to assess the compositional diversity of the volcanic sources around Gale crater, the effects of transport processes on the sediment grains, and the volumes and geochemistry of water that transported and cemented the sediments. The first study uses orbital mapping of a distinctive cemented boxwork layer on Mount Sharp to constrain a minimum volume of groundwater available to form this layer, 1 km above the modern floor of Gale, with implications for the formation of Mount Sharp. The other three studies use Curiosity rover imagery and geochemical data to investigate sedimentary rocks in Aeolus Palus and at the base of Mount Sharp. The second study identifies and describes diagenetic synaeresis cracks in the Sheepbed mudstone, at the lowest elevation in Aeolus Palus, with implications for the duration of water saturation of these lake sediments. The third and fourth studies identify and explain geochemical trends in the fluvio-deltaic Bradbury group, the Murray mudstone formation, and the eolian Stimson sandstone, focusing on geochemical diversity in the source regions for each of these units and how different depositional processes are reflected in the geochemical data. The sedimentary system in Gale crater has changed our understanding of Mars by expanding the known variety of igneous rocks, increasing estimates of the longevity of surface water lakes, and showing that there were once habitable environments on our neighboring planet.
47
"Breaking Ground on the Moon and Mars: Reconstructing Lunar Tectonic Evolution and Martian Central Pit Crater Formation." Doctoral diss., 2016. http://hdl.handle.net/2286/R.I.38606.
Full textAbstract:
abstract: Understanding the structural evolution of planetary surfaces provides key insights to their physical properties and processes. On the Moon, large-scale tectonism was thought to have ended over a billion years ago. However, new Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) high resolution images show the Moon’s surface in unprecedented detail and show many previously unidentified tectonic landforms, forcing a re-assessment of our views of lunar tectonism. I mapped lobate scarps, wrinkle ridges, and graben across Mare Frigoris – selected as a type area due to its excellent imaging conditions, abundance of tectonic landforms, and range of inferred structural controls. The distribution, morphology, and crosscutting relationships of these newly identified populations of tectonic landforms imply a more complex and longer-lasting history of deformation that continues to today. I also performed additional numerical modeling of lobate scarp structures that indicates the upper kilometer of the lunar surface has experienced 3.5-18.6 MPa of differential stress in the recent past, likely due to global compression from radial thermal contraction.
Central pit craters on Mars are another instance of intriguing structures that probe subsurface physical properties. These kilometer-scale pits are nested in the centers of many impact craters on Mars as well as on icy satellites. They are inferred to form in the presence of a water-ice rich substrate; however, the process(es) responsible for their formation is still debated. Previous models invoke origins by either explosive excavation of potentially water-bearing crustal material, or by subsurface drainage of meltwater and/or collapse. I assessed radial trends in grain size around central pits using thermal inertias calculated from Thermal Emission Imaging System (THEMIS) thermal infrared images. Average grain size decreases with radial distance from pit rims – consistent with pit-derived ejecta but not expected for collapse models. I present a melt-contact model that might enable a delayed explosion, in which a central uplift brings ice-bearing substrate into contact with impact melt to generate steam explosions and excavate central pits during the impact modification stage.Dissertation/Thesis
Doctoral Dissertation Geological Sciences 2016
48
Milam, Keith Alan. "Mapping the Martian Geologic Record: Studies of the Gusev Crater Spirit Landing Site and Plagioclase Feldspar Compositions on Mars." 2007. http://trace.tennessee.edu/utk_graddiss/246.
Full textAbstract:
The flurry of activity involved in the scientific study of Mars has resulted in multiple new data sets from several missions (Mars Global Surveyor (MGS), Mars Odyssey (MO), Mars Exploration Rovers (MER), Mars Reconnaissance Orbiter (MRO), and Mars Express) that provide information for unlocking the planet’s geologic and climatic history.
This three part study utilized both orbital data and laboratory experiments to examine Mars for morphologic and mineralogic evidence of aqueous activity and magmatic evolution.
The first study examined Gusev Crater, landing site for the Spirit MER rover. This work began during final landing site selection and was published just prior to Spirit’s January 2004 landing. In this work, I examined the paradigm that Gusev once held a paleolake and that it contains detrital sediment from the northern highlands. Analyses involved using the most current data then available. I produced thermophysical, morphological, and surface unit maps showing the spatial distribution and stratigraphic relationships of materials on the floor of Gusev. Orbital analyses found no unambiguous evidence of paleolake deposits. This study offered alternative hypotheses explaining floor units, one of which, volcanic deposition, has since been verified by Spirit on the ground.
The second and third studies address our ability to accurately derive plagioclase compositions on Mars and to use thermal emission spectroscopy to map vii the distribution of plagioclase compositions on Mars. Plagioclase is the most abundant mineral in the martian crust and may provide information about the igneous evolution and subsequent alteration of the Martian surface. The second study focuses on mixtures more complex in nature than the two-component (composition) plagioclase sand mixtures used in previous work. Linear deconvolutions of laboratory spectra from mixtures involving additional components and phases were used to calculate average plagioclase compositions whose accuracies were found to be comparable to previous studies. The final project carried results from previous laboratory studies one step further to map the global distribution of plagioclase compositions on Mars. Maps reveal a world dominated by labradorite and bytownite, with lesser amounts of other plagioclase. Localized variations are difficult to discern at the scale of individual MGS Thermal Emission Spectrometer (TES) observations.