Techn. Universiẗat, Diss., 2006--Darmstadt.

We have used Cassini measurements of electron density from Saturn's magnetosphere to search for a plasma tail behind the moon Titan. Such a plasma tail would consist of plasma that manage to escape Titan's gravitational pull and leave Titan's ionosphere to contribute to the plasma distribution in the Saturn system. The Cassini spacecraft was in orbit around Saturn for 13 years and performed 127 close flybys of Titan as well as many passes through Titan's orbit within the planets plasma-filled magnetosphere. We have used measurements of electron density from the Langmuir probe instrument, built by the Swedish Institute of Space Physics in Uppsala to search for such a tail. The data was analyzed in terms of looking at the spatial distribution of plasma around Titan and Saturn by examining the plasma density in Titan’s orbit in comparison to the rest of system, as well as comparisons of plasma density in front of Titan and behind Titan. The analysis provided no evidence of an extended plasma tail or torus.

The presented study deals with the sol-gel synthesis of nanocrystalline ternary phases of the general formula ZnxTiyOz, their characterization and potential application in photonics. Achieved results brings new fundamental knowledge about the processes leading to the formation of ZnxTiyOz nanocrystals from amorphous xerogels and gives novel information about structural and opto-electrical properties of prepared materials. Based on the presented results, most of all up-to-date reported ZnxTiyOz compounds with tailored nanocrystalline size and structure can be prepared as powders or thin films. Two sol-gel approaches based on the cluster process and direct heteronucleation were employed to prepare initial sol. Sols were optionally doped by Eu3+ ions to evaluate the effects of rare earth element to crystallization properties of formed compounds. In the first part of our study crystallization properties and structural evolution of thermally treated xerogels were analyzed. As a result a versatile method allowing the preparation of inverse spinel Zn2TiO4, cubic defect spinel ZnTiO3 and rhombohedral ZnTiO3 with tailored nanocrystal sizes was established. Initial composition and thermal annealing allow us to prepare selected ternary phase with tailored nanocrystal size ranging from tens of nanometers up to...

When the big joints like a knee or hip joint are damaged, the solution of this problem is an artificial substitute. The replacement of damaged joints with endoprotesis helps to reduce the pain and to move normally. In the design of the implant is necessary to fulfil all requirements on the properties of the material. The surface of implant is important, because it is directly connected to bone tissue. After implantation, the negative effect include infection, inflammation or release of the implant due to limited osseointegration, may appear. The osseointegration can be improved by modifying the material surface. This thesis is focused on development and evaluation of advanced materials imitating the bone structure, especially nanoroughness and the presence of biomimetic component, such as hydroxyapatite. In this study is evaluated adhesion, proliferation, viability, differentiation, and synthesis of specific proteins of human osteoblasts like Saos-2 on titanium modified with nanotubes and plasma sprayed hydroxyapatite compared with smooth surfaces. Key words: titanium, nanotubes, osteoblasts, hydroxyapatite, nanoroughness

Despite atmospheric and compositional differences on Titan and Earth, the similarity in the shape and spacing of linear dunes of the Belet Sand Sea of Titan and the Namib Sand Sea of Earth suggests that comparisons will yield a better understanding of the dictating factors of duneforming processes. We present a methodology for the collection of dune width and spacing measurements representative of the Namib and Belet sand seas. 94,304 locations in Belet from Cassini SAR images and 5,563 locations in the Namib from IKONOS images are used for measurements. The average width and spacing of linear dunes in Belet are 1,235 m and 2,776 m, respectively, with a standard deviation of 422 and 859 respectively. In the Namib, the average linear dune width and spacing is 736 m and 2,203 m, with a standard deviation of 204 and 592. We also analyze these morphometrics according to potential dictating factors such as elevation and distance to sand sea margins. We establish significant trends according to distance to margin, which confirms that the largest and most widely spaced dunes are generally found in the center of the sand sea. We also observe increasing dune width with increasing elevation. The strongest trend we observe is distance to the western margin in the Namib Sand Sea. In Belet, none of these trends were found to be significant. Analysis of width vs. spacing is significant in both sand seas. The disparity in results of the two sand seas suggests factors such as age, sand sea size, or proximity to source may influence linear dune morphometrics.

Ion chemistry has become increasingly important in the evolution of the chemical inventory of extraterrestrial environments. Isomers of ions have also come to play an important role as, in many instances, the cold environments in the interstellar medium and high layers of planet and satellite atmospheres do not supply enough energy to overcome isomerization barriers and the isomers effectively act as separate molecules.  In this licentiate thesis, several studies of the [CH3N]+ isomers are presented. Reactivity studies of the two isomers, the methanimine radical cation (H2CNH+) and aminomethylene (HCNH2+) with hydrocarbons C2H4, C2H2 and CH4, and IRPD spectroscopy of both species have been performed. Complimentary ab initio calculations aid in the determination of formation pathways of observed product channels and in the assignment of the vibrational bands seen in the IRPD spectrum. The results show that reaction pathways of the two isomers generally involve adduct formation followed by hydrogen ejection where the product or pathway is dependent on the ingoing reactant isomer. The IRPD spectrum allows identification of the different isomers via vibrational transitions. Isomer generation by electron ionization favours methanimine cation production with an abundance of 70% while with VUV photoionization it is possible to selectively produce isomers. It is concluded that isomerism must be considered when investigating the chemical environment of interstellar objects.

The main focus of this work was to get a deeper understanding of the relationship between the structure of sol-gel films, their densification and their macroscopic cracking. First of all titania was chosen as model system. Therefore a synthesis route starting from the preparation of long-term stable amorphous redissoluble precursor powders based on acetylacetone as chelate ligand was utilized. The solubility and stability of the powders in various solvents can be determined by chemical synthesis and technological parameters. When dissolved in a solvent mixture of ethanol and 1,5-pentanediol, thin films can be easily prepared by dip-coating technique. Thereby the quality of the titania films enormously depends on the calcinations temperature and the solvent mixture is used. In order to investigate the influence of different solvents and solvent mixtures on the microstructure and densification of the precursors, the coating solutions were stripped off (sol powder) and analyzed as function of annealing temperature. It was pointed out that a high densification rate caused by the addition of 1,5-pentanediol, results in dense microstructure with trapped residual carbon. These impurities can retard the phase transformation of anatase to rutile. The analysis of so-called “film powders” scraped off multiple dip-coated substrates provides valuable information on the effect of air moisture and unidirectional densification during drying and aging on the structure of thin films. The high surface-to-volume ratio and access to air moisture determine the chemical composition of the as-prepared film, which controls shrinkage, crystallization and defect structure of the coatings. Further it was shown, that drying as a thin film results in the formation of closed pores and much denser microstructure than the respective sol powder. Without the addition of 1,5-pentanediol all –OEt moieties undergo hydrolysis reactions, which causes the formation of a rigid network. The presence of 1,5-pentanediol retards this hydrolysis reactions and provides some network plasticity. Generally the microstructure of thin films is comparatively close to the microstructure of the film powders. The addition of 1,5-pentandiol prevents hydrolysis and condensation reactions as like in the film powders. However even at 700 °C, thin films never transform to rutile, which was attributed to the tensile stresses in thin films. In thin films and in film powders as well a comparable amount of closed pores are formed during annealing. Further it was shown that most of the thin sol-gel films investigated form a dense crust on their tops during annealing. This explains why crack free films exhibit only closed pores. However, when cracks appear during thin film shrinkage in the coating, this crust is burst, which generates open porosity. The defect density in the coatings was determined by an automated analysis of surface images. The crack formation and quantity can be directly referred to tensile stresses in the coatings, which arise from hydrolysis and condensation during thin film drying and aging. Therefore when 1,5-pentanediol is added to the sol, thin film cracking was avoided, because hydrolysis and condensation reactions are retarded, which preserves a higher network flexibility. Furthermore the crack formation was significantly influenced by the atmospheric humidity that was used during the coating process, which was explained by different drying and condensation rates. Under certain chemical starting conditions water soluble precursor powders can be also obtained. In general the observations made with the water based coating solutions are mostly in agreement with the former results based on ethanol based coating solutions. For example the high surface-to-volume ratio of film powders compared to sol powders also significantly enhances film drying and densification. The addition of 1,5-pentanediol also clearly contributes to their densification behavior and phase evolution. As seen before in the case of ethanol based coatings, 1,5-pentanediol enhances the stability towards hydrolysis and condensation reactions and preserves some network plasticity. Therefore coatings prepared without the addition of 1,5-pentanediol already form cracks during film drying and aging because of tensile stresses. Thus, the addition of 1,5-pentanediol results in a reduction/prevention of crack formation. Nevertheless some differences were observed, i.e. the critical single coating film thickness of ethanol based coatings is nearly twice that of water based coatings. This was explained by the different surface tensions of the basis solvents, which during thin film drying causes significantly higher capillary forces and tensile stresses in water based coatings. When acetylacetone is replaced by triethanolamine as chelating ligand for titanium also re-dissolvable precursor powders can be synthesized. The film powders combine a high hydrolytic stability of the precursor with sufficient intermediate network flexibility. The different type of organics changes the drying and densification behavior: i.e. in contrast to film powders obtained from acetylacetone based precursor powders the structure of triethanolamine based film powders is unaffected by the thin film drying process. This high hydrolytic stability and plasticity of this precursor allows the preparation of defect free coatings up to single film thickness of 300 nm. However triethanolamine based thin films present at intermediary annealing temperatures a distinctively different microstructure compared to acetylacetone based films. The general validity of the conclusions was proved on the basis of zirconia coatings that were also prepared by the use of re-dissolvable precursor powders. In principle all conclusions concerning the interconnection of precursor chemistry, film formation, densification and structure were transferable to the respective zirconia coatings. Differences mainly arise only from differential material properties i.e. bulk density. Finally, it has been pointed out that the findings obtained on the densification behavior of thinsol-gel films are also a valuable tool for improved explanations of other important scientific questions concerning sol-gel films, i.e. scratch resistance of sol-gel coatings, fiber -bridging and – degradation of sol-gel coated fibers. / Grundsätzlich war es Ziel der vorliegenden Arbeit, die Zusammenhänge zwischen Struktur von Sol-Gel Schichten, ihrer Verdichtung und der Entstehung von makroskopischen Rissen besser verstehen zu können. Als Modelsystem wurde hierfür Titanoxid ausgewählt. Hierzu wurde von einer Syntheseroute basierend auf der Verwendung von langzeitstabilen amorphenre-dispergierbaren Vorstufenpulvern mit Acetylaceton als Chelatligand ausgegangen. Die Löslichkeit und Stabilität der Pulver in verschiedenen Lösungsmitteln lässt sich über die chemische Synthese bzw. technologischen Parameter einstellen. Wenn die Pulver in einem Lösungsmittelgemisch aus Ethanol und 1,5-Pentandiol gelöst werden, lassen sich mittels Tauchbeschichtungsverfahren einfach dünne Schichten herstellen. Die Qualität der Titanoxidschichten hängt dabei entscheidend von der verwendeten Pyrolysetemperatur und der Menge an verwendetem 1,5- Pentandiol ab. Um den Einfluss von verschiedenen Lösungsmitteln und Lösungsmittelgemischen auf die Mikrostruktur und Verdichtung der Vorstufen zu untersuchen, wurden die Sole am Rotationsverdampfer eingeengt (Sol-Pulver) und in Abhängigkeit von der Behandlungstemperatur analysiert. Dabei stellte sich heraus, dass eine hohe Verdichtungsrate verursacht durch den Zusatz von 1,5-Pentandiol, in einer dichten Mikrostruktur mit eingeschlossenem Rest-Kohlenstoff resultiert. Diese Kohlenstoff-Rückstände können die Phasenumwandlung von Anatas zu Rutil hemmen. Die Analyse der so genannten „Film-Pulver“, welche von mehrfach tauchbeschichteten Substraten abgekratzt worden sind, ermöglicht den Zugang zu entscheidenden Informationen über den Einfluss der Luftfeuchtigkeit und der unidirektionalen Verdichtung, während der Film-Trocknung und –Alterung, auf die Struktur der dünnen Schichten. Es zeigte sich, dass das große Oberfläche zu Volumen Verhältnis und der Kontakt mit Luftfeuchtigkeit die chemische Zusammensetzung der frisch hergestellten Schichten bestimmen. Diese wiederum steuert die Schichtschrumpfung, Kristallisation und Defektstruktur der Schichten. Ferner konnte dargestellt werden, dass die Trocknung als dünner Film zu der Entstehung von geschlossenen Poren und zu einer deutlich dichteren Mikrostruktur als die der entsprechenden Sol-Pulver führt. Ohne den Zusatz an 1,5-Pentandiol kommt es zur Hydrolyse der –OEt Gruppen, was die Bildung eines rigiden Netzwerks bewirkt. 1,5-Pentandiol als Zusatz hemmt diese Hydrolysereaktionen und bedingt damit eine gewisse Plastizität des Netzwerkes. Im Großen und Ganzen ist die Mikrostruktur der dünnen Schichten mit der Struktur der Film-Pulver gut vergleichbar. Durch den Zusatz an 1,5-Pentandiol werden in den Schichten die Hydrolyse und Kondensationsreaktionen ebenso gehemmt wie in den entsprechenden Film-Pulvern. Allerdings bei den dünnen Schichten ist auch bei 700 °C keine Phasenumwandlung zu beobachten, was auf Zugspannung in den dünnen Filmen zurückzuführen ist. Während der Calcinierung kommt es sowohl in dünne Schichten wie als auch in den Film-Pulvern zur Ausbildung von geschlossenen Poren. Ferner wurde gezeigt, dass die meisten untersuchten dünnen Schichten während der Pyrolyse auf ihrer Oberfläche eine dichte Kruste ausbilden. Dies erklärt warum rissfreie Schichten nur geschlossene Poren aufweisen. Allerdings wenn Risse während der Schichtschrumpfung in der Schicht auftreten, wird diese Kruste durchbrochen, was zur Bildung von offener Porosität führt. Die Defektdichte in den Schichten wurde mittels einer automatisierten Bildanalyse der Oberfläche bestimmt. Die Riss-Bildung und Riss-Häufigkeit kann dabei direkt mit der Entstehung von Zugspannung, durch Hydrolyse und Kondensation während der Schicht-Trocknung und –Alterung, in Zusammenhang gebracht werden. Durch die Zugabe von 1,5-Pentandiol konnte die Rissentstehung verhindert werden, da Hydrolyse und Kondensations-Reaktionen gehemmt werden, was eine höhere Flexibilität des Netzwerkes erhält. Weiterhin wurde die Rissentstehung signifikant durch die herrschende Luftfeuchtigkeit während es Beschichtungsprozesses beeinflusst, was mit unterschiedlichen Hydrolyse- und Kondensations-Raten zu erklären ist. Unter Verwendung bestimmter chemische Syntheseparameter, können ebenso wasserlösliche Vorstufenpulver erhalten werden. Grundsätzlich sind die Untersuchungen an den hieraus resultierenden wässrigen Solen und Schichten in guter Übereinstimmung mit den vorherigen Untersuchungen an ethanolischen Beschichtungssystemen. So zum Beispiel, beschleunigt ebenso das große Oberfläche zu Volumen Verhältnis der Film-Pulver deutlich die Film-Trocknung und –Verdichtung, im Vergleich zu den Sol-Pulvern. Auch beeinflusst ein Zusatz an 1,5-Pentandiol eindeutig das Verdichtungsverhalten und die Phasenentwicklung. Wie schon bereits im Fall der Ethanol basierenden Beschichtungen festgestellt worden ist, erhöht 1,5-Pentandiol die Beständigkeit hinsichtlich Hydrolyse und Kondensationsreaktionen und erhält hiermit eine gewisse Netzwerkplastizität. Deshalb bilden Filme die ohne einen Zusatz an 1,5-Pentandiol hergestellt worden sind, aufgrund von Zugspannung, schon während der Film-Trocknung und -Alterung Risse aus. Durch einen Zusatz von 1,5-Pentandiol kann dagegen die Entstehung von Rissen vermindert bzw. vermieden werden. Allerdings zeigten sich auch einige Unterschiede: So ist zum Beispiel die erreichbare Einzelschichtdicke der ethanolischen Beschichtungssystemen nahezu doppelt so groß wie die der wässrigen Beschichtungssysteme. Dies wurde mit der unterschiedlichen Oberflächenspannung des Basislösungsmittels erklärt, welche während der Schichttrocknung deutlich höhere Kapillarkräfte und Zugspannung in wässrigen Filmen erzeugt. Wird Acetylaceton gegen Triethanolamin als Chelatligand für Titan ausgetauscht, so können ebenso re-dispergierbare Vorstufenpulver hergestellt werden. Die Film-Pulver kombinieren hohe hydrolytische Stabilität der Vorstufe mit einer ausreichenden intermediären Netzwerkflexibilität. Der andere Komplexbildner verändert entscheidend das Trocknungs- und Verdichtungs-Verhalten: so z.B. wird die die Struktur von Film-Pulvern basierend auf Triethanolamin nicht entscheidend durch die Trocknung als dünne Schicht beeinflusst, im Gegensatz zu Film-Pulvern hergestellt von Vorstufenpulvern mit Acetylacetone als Chelatligand. Diese hohe hydrolytische Stabilität und Plastizität der Vorstufe ermöglicht die Herstellung von defektfreien Beschichtungen bis hin zu einer Einzelschichtdicke von 300 nm. Dennoch unterscheidet sich bei intermediären Pyrolysetemperaturen die Mikrostruktur der Triethanolamin basierenden Schichten deutlich von der auf Acetylaceton basierenden Schichtsystemen. Die Allgemeingültigkeit der Schlussfolgerungen wurde anhand Zirkonoxidbeschichtungen, welche ebenfalls unter Verwendung von löslichen Vorstufenpulvern hergestellt worden sind, überprüft. Grundsätzlich zeigte sich hierbei, dass alle Schlüsse hinsichtlich der Zusammenhänge der Vorstufenchemie, Film-Bildung, -Verdichtung und –Struktur auf die entsprechenden Zirkonoxidbeschichtungen übertragbar sind. Unterschiede ergeben sich nur aus unterschiedlichen Materialeigenschaften wie z.B. der makroskopischen Dichte. Letztlich wurde dargestellt, dass die Erkenntnisse hinsichtlich des Verdichtungsverhalten der Sol-Gel Schichten die Grundlage für die Aufklärung vieler anderer wichtiger wissenschaftlich Fragestellungen hinsichtlich Sol-Gel Beschichtungen bilden, wie z.B. der Kratzfestigkeit von Sol-Gel Schichten, Faser-Verbrückung und -Schädigung von Sol-Gel beschichten Fasern.

This thesis aims to investigate the potential of a transfer orbit using successive aerocaptures at Saturn and Titan to establish a science orbit around Titan. Titan is an Earth-like moon with a dense atmosphere and organic compounds present. It has many similarities with Earth that are useful to study such as superrotation. Superrotation is when the atmosphere rotates faster than the body it surrounds. In order to study Titan, we need to establish an orbit around it. The Saturn system is distant from Earth, 8.5 Astronomical Units (AU) which makes it difficult to reach from a time and velocity point of view. We propose to use an aerocapture at Saturn to intercept Titan with lower relative velocity in order to perform an aerocapture at Titan. The analysis was performed in primarily MATLAB to simulate the orbits. The results of this showed that we can aerocapture a spacecraft at Saturn and arrive at Titan within roughly 4 to 8 km/s relative velocity regardless of the incoming hyperbolic excess velocity at the Saturn system. This can be improve upon by using intermediate transfer orbits, such as bi-elliptics, to arrive with even lower relative velocities to Titan of as low as 1 km/s. The drag acceleration experienced during the Saturn aerocapture had peak values of between 0.2 and 1.4 g's and acceleration over 50% of the peak is experienced between 6.8 and 8 minutes. This capture method has the potential to make Titan more easily accessible and allow for scientific study of a clear target for improving our understanding of Earth-like processes on other bodies in our solar system. / Master of Science / This thesis aims to investigate the potential of a transfer orbit using successive aerocaptures at Saturn and Titan to establish a science orbit around Titan. Aerocapturing is utilizing the atmosphere of a body to slow down a spacecraft. Titan is an Earth-like moon with a dense atmosphere and organic compounds present. It has many similarities with Earth that are useful to study such as superrotation. Superrotation is when the atmosphere of a body rotates faster than the body it surrounds. In order to study Titan, we need to establish an orbit around it. The Saturn system is distant from Earth, 8.5 Astronomical Units (AU) which makes it difficult to reach from a time and velocity point of view. It takes a large amount of time to get there so we attempt to get there faster by increasing velocity. This means we arrive at the Saturn system with a large amount of velocity that we need to counter-act in order to orbit. We propose to use an aerocapture at Saturn to intercept Titan with lower velocity in order to perform another aerocapture at Titan to slow into an orbit. The analysis was performed in primarily MATLAB to simulate the orbits. The results of this showed that we can aerocapture a spacecraft at Saturn and arrive at Titan within roughly 4 to 8 km/s regardless of the incoming velocity to the Saturn system. This can be improve upon by using intermediate transfer orbits, after capturing at Saturn, to arrive with even lower velocities at Titan of as low as 1 km/s. The drag acceleration experienced during the Saturn aerocapture had peak values of between 0.2 and 1.4 g's and acceleration over 50% of the peak is experienced between 6.8 and 8 minutes. This is relatively gentle for an aerocapture and means the spacecraft likely will not require significant structural support. This capture method has the potential to make Titan more easily accessible and allow for scientific study of a clear target for improving our understanding of Earth-like processes on other bodies in our solar system.

Analyzing dune parameters such as dune width and spacing can be useful in determining the reaction of dunes to changes in atmospheric and sedimentary conditions currently and in the recent geologic past. Dune parameters, dune width and spacing, were measured for linear dunes in regions across Saturn's moon Titan from images T21, 23, 28, 44 and 48 collected by Synthetic Aperture RADAR aboard the Cassini spacecraft in order to reconstruct the surface history of Titan. Dunes in the five study swaths are all linear in form, but lack superimposed or flanking dunes. They have a mean width of 1.3 km and mean crest spacing of 2.7 km, wider and farther apart on average than similar terrestrial dunes in the Namib and Agneitir Sand Seas though larger linear dunes exist on Earth. Because of the lack of superimposed and flanking dunes and their size, Titan's dunes are classified as very large simple linear dunes. The large size, spacing and uniform morphology are all indicators that Titan's dunes are very mature and long-lived features. The ratio of dune width to spacing for Titan's dunes is similar to that found in terrestrial dunes in that dune spacing tends to be twice dune width. In addition to being similar in size, this is further evidence that terrestrial dunes can be used as analogues for Titan's dunes and vice versa and that the essential dune-forming processes are the same on both bodies. Dune width and spacing decrease northward, which is attributed to, but not limited to, increased maturity of dune fields to the south or increased sediment stabilization to the north. Sediment stabilization may be caused by Titan's asymmetric seasons and a net transport of moisture from south to north. The majority of dunes have spacings consistent with an upper limit of 2 to 4 km established by the atmospheric boundary layer, further evidence they are mature. Dunes are more widely spaced in the south are evidence they have been growing toward a steady state for a longer period of time than those in the north. Titan's large linear dunes have long reconstitution times. This is in part due to the fact that winds sufficient for saltation are reached only near the Titan equinox every 14 Earth years. Based on rates for similar terrestrial dunes the reconstitution time for Titan's dune is 600,000 Earth years or more, and therefore substantial changes in dune form should not be observable over Cassini's lifetime. Cumulative probability plots of dune parameters measured at different locations across Titan indicate there is a single population of dunes on Titan. This suggests that, unlike analogous dunes in the Namib and Agneitir Sand Seas, dune-forming conditions that currently exist on Titan are either the only dune-friendly conditions in the moon's history, or the current conditions have been stable and active long enough to erase any evidence of past conditions.

Titan is an important planetary body for aeolian research because of the vast equatorial sand seas that span 20% of its surface. Previous studies have determined the general margins of sand and sand seas on Titan, and have speculated about the source of Titan's sand. Little research has been done concerning where sand collects in the sand seas. Additionally, the relationships be-tween material distributions as observed by the Cassini Visual and Infrared Mapping Spectrometer (VIMS) and the history of erosion and transportation of sediments across equatorial latitudes is not fully understood. This work focuses on an in depth evaluation of sand distribution and abundance across the sand seas, and presents evidence for an alternative sand source. This work also addresses a potential stratigraphy for the equatorial regions based on the excavation of materials from impact craters. We mapped the extent of relative sand abundances by comparing different Cassini image datasets, largely by mapping where the Imaging Science Subsystems (ISS) regions were darkest, in-dicating the presence of more sand. Our results revealed that greater abundances of sand accumu-late near the eastern margins of sand seas. This is in agreement with previous studies that demon-strated general W to E transport, and fits a general model of sand transport across the sand seas to collect at the downwind margins, perhaps ahead of topographic obstacles that mark the eastern ends of the sand seas. Additionally, we found that the largest continuous expanse of abundant sand de-posits lie across Belet, a large sand sea that occupies a broad equatorial lowland. Another sand sea of interest is Shangri-La, which has a recessed SE margin adjacent to the broad, albedo-bright de-pression Xanadu. We also found abundant sand deposits within Shangri-La across a corridor be-tween highlands and along the SE boundary of the sand sea. Dune crest orientations across eastern Shangri-La indicate WNW to ESE transport in the region. We propose that the low topography of Xanadu, coupled with the strong gradient in albedo between Shangri-La and Xanadu would gener-ate atmospheric disturbances similar to those responsible for transporting sand across positive changes in elevation on Mars, and may be responsible for the distinct boundary. VIMS-blue materials are generally associated with water ice mixed with organic com-pounds. We found that VIMS-blue surfaces across equatorial latitudes tend to be directly adjacent to and upwind of sand seas. This, coupled with geomorphological observations of erosional charac-teristics and examination of material properties, suggests that sand could at least in part be derived from VIMS-blue materials. We propose 3 environments (alluvial fans, dry lakebeds, and ejecta from impact craters) for sand production using this interpretation and making comparisons with SAR, ISS, and VIMS imagery. Modeling suggests that Titan's lithosphere significantly thickened 500 m.y. ago. We inter-pret an elongate exposure of VIMS-blue materials adjacent to Aztlan to be a rift caused by a thick-ening of the lithosphere, similar to many of the other icy bodies of the solar system. Our interpreta-tion is further supported by the distribution of cryovolcanic features alongside the proposed rift. Anomalous VIMS-blue and bright regions within eastern Xanadu are distributed in a pattern that resembles a multi-ringed impact basin. Additionally, when a value threshold was applied to ISS imagery, a bright circular feature was revealed within western Xanadu. These observations suggest two large impacts may have been significantly responsible for creating Xanadu. Comparisons of impact crater models with VIMS imagery of Paxsi, Menrva, Sinlap, Selk, and other craters suggest alternating layers of VIMS-bright and VIMS-blue cover much of the equatorial latitudes of Titan. We completed ground penetrating radar (GPR) and global positioning system (GPS) surveys across margins of the Kelso Dunes to evaluate the effects of fluvial interaction on sand depth. Our terres-trial model was compared to sand seas on Titan that appear to also have interactions with fluvial channels. Distributions of sand suggest that in both the Kelso Dunes and on Titan, fluvial obstruc-tion is temporary and on Titan isolated across small regions. This work leads to a better understanding of sand production, accumulation and transport on Titan and in sand seas in general, and reveals a basic stratigraphy of the equatorial regions of Titan. This region is of particular interest because it is the landing site of the Dragonfly mission, now in design.