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Titan's bright, hummocky and mountainous terrain shows ridges and mountains, such as seen in the T8 swath. The ridge-like features that are part of this unit are highlighted in yellow in the lower figure. Other radar-bright units that are not highlighted are considered part of the undifferentiated plains, as the resolution was not sufficient for these areas to be unambiguously mapped. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
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The Cassini Titan Radar Mapper is providing an unprecedented view of Titan’s surface geology. Here we use Synthetic Aperture Radar (SAR) image swaths (Ta–T30) obtained from October 2004 to December 2007 to infer the geologic processes that have shaped Titan’s surface. These SAR swaths cover about 20% of the surface, at a spatial resolution ranging...
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... et al. (2008) modeled the feature as a viscously emplaced dome between 2 and 5 km in height. However, recent topographic results using SAR stereo ) and overlapping SAR beams ( Stiles et al., 2009) showed (50N, 87W), showing the 180-km diameter structure on the left (west) and numerous overlapping flows to the north and east, including Leilah Fluctus, the radar-bright flows to the east that have been interpreted as fluvial in origin ( Paganelli et al., 2005). Data from the Ta and T23 flybys. ...
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... surface has numerous patches of radar-bright, textured terrains that have been interpreted to be of tectonic origin (Radeb- augh et al., 2007). Among these features are ridge-like features (Fig. 5), elevated blocks which stand generally isolated, and mountainous and hummocky terrain. Hummocky and mountainous terrain consists of isolated patches of radar-bright hummocky material, hills, mountain chains, and blocks. This terrain is mostly found as isolated patches or long mountain chains. In general, the patches of bright, hummocky ...
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Now the entire surface of Mars is bound by permafrost. Its thickness reaches one kilometer at the equator and increases to six kilometers at the poles. However, ravines formed by water flows and mud flows inside some craters indicate the release of liquid from the melted layer of permafrost. Changes in the appearance of some ravines can be formed b...
Citations
... [178]). Refer to Lopes et al. [251] for more details. (b) Color-coded topographic map overlaid on a mosaic of SAR and high-altitude SAR images covering a southern polar region of Titan, derived from Cassini radar stereo analysis [178]. ...
Planetary mapping product established by topographic remote sensing is one of the most significant achievements of contemporary technology. Modern planetary remote sensing technology now measures the topography of familiar solid planets/satellites such as Mars and the Moon with sub-meter precision, and its applications extend to the Kuiper Belt of the Solar System. However, due to a lack of fundamental knowledge of planetary remote sensing technology, the general public and even the scientific community often misunderstand these astounding accomplishments. Because of this technical gap, the information that reaches the public is sometimes misleading and makes it difficult for the scientific community to effectively respond to and address this misinformation. Furthermore, the potential for incorrect interpretation of the scientific analysis might increase as planetary research itself increasingly relies on publicly accessible tools and data without a sufficient understanding of the underlying technology. This review intends to provide the research community and personnel involved in planetary geologic and geomorphic studies with the technical foundation of planetary topographic remote sensing. To achieve this, we reviewed the scientific results established over centuries for the topography of each planet/satellite in the Solar System and concisely presented their technical bases. To bridge the interdisciplinary gap in planetary science research, a special emphasis was placed on providing photogrammetric techniques, a key component of remote sensing of planetary topographic remote sensing.
... The mapping presented here follows the general principles of previous Titan mapping (e.g., Stofan et al., 2006) and is a continuation of the detailed geomorphological mapping effort presented in Malaska, Lopes, Williams, et al. (2016) and Schoenfeld et al. (2021). For this paper, we are particularly interested in examining the transition between the equatorial and mid-latitude terrains (such as mapped by Lopes et al. (2010), Malaska, Lopes, Williams, et al. (2016), and Schoenfeld et al. (2021)) and the high latitude regions mapped by Birch et al. (2017). We used the Cassini's Synthetic Aperture Radar (SAR) data as the basemap, but we also incorporated information from non-SAR data sets, including microwave emissivity, topography, visible and infrared reflectance. ...
... The SAR swaths were mosaicked and loaded into the ArcGIS™ 10.6 (ESRI) software package and then used to categorize the surface based on morphological and backscatter properties. Contacts between terrains of different radar backscatter or morphological signatures were drawn, the boundaries being determined by following procedures described in previous studies (e.g., Birch et al., 2017;Lopes et al., 2010Lopes et al., , 2016Malaska, Lopes, Williams, et al., 2016;Schoenfeld et al., 2021;Stofan et al., 2007;Williams et al., 2011). We defined gradational contacts between units if a clear delineation could not be made at the resolution of the SAR images (∼1 km). ...
We mapped the Soi crater region at 1:800,000 scale and produced a geomorphological map using methodology presented by Malaska, Lopes, Williams, et al. (2016), https://doi.org/10.1016/j.icarus.2016.02.021 and Schoenfeld et al. (2021), https://doi.org/10.1016/j.icarus.2021.114516. This region spans longitude 110° to 180°W and latitude 0° to 60°N and is representative of the transition between the equatorial, mid‐latitude, and high‐latitude northern regions of Titan. We used Cassini Synthetic Aperture Radar (SAR) as our primary mapping data set. For areas where SAR was not available, we used lower resolution data from the Imaging Science Subsystem, the Visible and Infrared Mapping Spectrometer, radiometry, and high‐altitude SAR for complete mapping coverage of the region. We identified 22 geomorphological units, 3 of which have been discussed in existing literature but have not yet been incorporated into our mapping investigations. These include sharp‐edged depressions (bse), ramparts (brh), and bright gradational plains (pgh). All six major terrain classes are represented in this region: Craters, Labyrinth, Hummocky/mountainous, Plains, Dunes, and Basin and Lakes. We find that plains dominate the surface of the Soi crater region, comprising ∼73% of the mapped area, followed by dunes (∼14%), mountains/hummocky terrains (∼12%), basin and lakes (∼0.7%), labyrinth terrains (∼0.5%), and crater terrains (∼0.4%). We also observe empty lakes as far south as 40°N. The Soi crater region largely has the same collection and proportion of geomorphological units to other mapped regions on Titan. These results further support the hypothesis that surface processes are, broadly speaking, the same across Titan's middle and equatorial latitudes, with the exception of Xanadu.
... Synthetic aperture radar (SAR) images revealed a relatively young surface covered by a multitude of geologic features (e.g. Elachi et al., 2005;Lopes et al., 2010;Lorenz et al., 2013). While liquid hydrocarbon lakes and seas have understandably received much attention (Hayes, 2016;Hayes et al., 2018;Mastrogiuseppe et al., 2019;Poggiali et al., 2020), there are a wide variety of landscapes on Titan's surface that also warrant further examination (Malaska et al., 2016a;Lopes et al., 2020). ...
... These terrains include those common to planetary surfaces such as craters and dune fields (Lorenz et al., 2006;Lucas et al., 2014;Malaska et al., 2016b), but also some terrains that are more exotic such as the potential remnants of cryovolcanism (Lopes et al., 2013). Herein, we investigate a set of common features with relatively high relief that have been classified as mountains, hummocks, or sometimes colles (Radebaugh et al., 2007;Lopes et al., 2010;Mitri et al., 2010;Cook-Hallett et al., 2015;Liu et al., 2016;Malaska et al., 2016a;Lopes et al., 2020). In this paper we will adopt the classification scheme described in Malaska et al. (2016a) and refer to the features in question as either mountains or hummocks. ...
... Mountains and hummocks are primarily identified by their appearance in SAR imagery and limited SARTopo observations (Radebaugh et al., 2007;Lopes et al., 2010;Cook-Hallett et al., 2015;Liu et al., 2016;Malaska et al., 2016a;Lopes et al., 2020). Both terrains have high radar backscatter relative to surrounding plains and can exist as isolated features or in chains covering large areas. ...
Mountain formation and evolution on Titan is poorly understood, due in part to a lack of high-resolution topographic data. By applying advanced processing techniques, we are able to increase the along-track spatial resolution of the Cassini RADAR altimeter by up to a factor of ten, enabling more detailed analysis. A survey of mountainous and hummocky terrain reveals a unique, characteristic waveform shape. By modeling reflections from different landscapes, we are able to show that these waveforms contain sub-resolution topographical information. We found that mountain elevation on Titan varies greatly over short distances, and evidence suggests that many mountain ranges on Titan have been eroded down to the plains level even within a single high-resolution radar footprint.
... The map units were grouped into five types: plains, highlands, units associated with crater materials, units associated with aeolian dunes, and units associated with channels and their outflows. Other maps of Titan at a global scale were subsequently presented by Lopes et al. (2010Lopes et al. ( , 2016Lopes et al. ( , 2020 and Malaska et al. (2020), and references therein), who characterized undifferentiated plains, variable featured plains, labyrinth terrains, fluvial channels, lakes, impact craters, and other crateriform structures, and dunes, some of them with differential spatial distribution according to the latitudes. ...
Titan is unique in the solar system: it is an ocean world, an icy world, an organic world, and has a dense atmosphere. It is a geologically active world as well, with ongoing exogenic processes, such as rainfall, sediment transportation and deposition, erosion, and possible endogenic processes, such as tectonism and cryovolcanism. This combination of an organic and an ocean world makes Titan a prime target for astrobiological research, as biosignatures may be present in its surface, in impact melt deposits and in cryovolcanic flows, as well as in deep ice and water ocean underneath the outer ice shell. Impact craters are important sites in this context, as they may have allowed an exchange of materials between Titan's layers, in particular between the surface, composed of organic sediments over icy bedrock, and the subsurface ocean. It is also possible that impacts may have favored the advance of prebiotic chemical reactions themselves, by providing thermal energy that would allow these reactions to proceed. To investigate possible exchange pathways between the subsurface water ocean and the organic-rich surface, we modeled the formation of the largest crater on Titan, Menrva, with a diameter of ca. 425 km. The premise is that, given a large enough impact event, the resulting crater could breach into Titan's ice shell and reach the subsurface ocean, creating pathways connecting the surface and the ocean. Materials from the deep subsurface ocean, including salts and potential biosignatures of putative subsurface biota, could be transported to the surface. Likewise, atmospherically derived organic surface materials could be directly inserted into the ocean, where they could undergo aqueous hydrolysis to form potential astrobiological building blocks, such as amino acids. To study the formation of a Menrva-like impact crater, we staged numerical simulations using the iSALE-2D shock physics code. We varied assumed ice shell thickness from 50 to 125 km and assumed thermal structure over a range consistent with geophysical data. We analyze the implications and potential contributions of impact cratering as a process that can facilitate the exchange of surface organics with liquid water. Our findings indicate that melt and partial melt of ice took place in the central zone, reaching ca. 65 km depth and ca. 60 km away from the center of the structure. Furthermore, a volume of ca. 10² km³ of ocean water could be traced to depths as shallow as 10 km. These results highlight the potential for a significant exchange of materials from the surface (organics and ice) and the subsurface (water ocean), particularly in the crater's central area. Our studies suggest that large hypervelocity impacts are a viable and likely key mechanism to create pathways between the underground water ocean and Titan's organic-rich surface layer and atmosphere.
... The spatial distribution of channels (Jaumann et al. 2008;Lorenz et al. 2008;Langhans et al. 2011;Black et al. 2017), the variability of their morphology with latitude or geomorphic region (Lorenz et al. 2008;Lunine & Atreya 2008;Burr et al. 2009;Lopes et al. 2010;Langhans et al. 2011;Black et al. 2012;Tewelde et al. 2013), and their spectral characteristics (Langhans et al. 2011) have all been classified to various degrees throughout the Cassini mission. However, due to Cassini's coarse resolution and limited coverage, we do not yet know whether there is systematic variation in morphologic type indicative of heterogeneities in the crust (e.g., tectonic control; Burr et al. 2013a) and/ or a variation in transport efficiencies or climate change (e.g., equatorial drying; Moore et al. 2014). ...
... When conducting this study, we had access to data sets with greater coverage and higher resolution than were available for previous studies (Jaumann et al. 2008;Lorenz et al. 2008;Burr et al. 2009;Lopes et al. 2010;Langhans et al. 2011;Burr et al. 2013a), and comparisons with earlier maps reflect these differences. There were some features such as raised lake rims that appeared channel-like at lower resolution (Burr et al. 2013a), but which we were able to determine were not channels because of newer, often higher-resolution data sets and the fact that we relied on individual SAR swaths instead of layered mosaics ( Figure 14). ...
Cassini Synthetic Aperture Radar (SAR) images of Titan’s surface revealed river networks strikingly similar to those on Earth. However, Cassini SAR has low spatial resolution and image quality compared to data used to map channels on Earth, so traditional methods for characterizing river networks might not yield accurate results on Titan. We mapped terrestrial analog networks with varying resolutions and image qualities to determine which geomorphologic metrics were invariant with scale or resolution. We found that branching angle and drainage density varied significantly with image resolution, and we therefore expect the actual drainage density of Titan’s channel networks to be significantly higher than the values calculated from Cassini data. Calculated network geometry did not change predictably with resolution and would therefore not be an ideal metric for interpreting Titan’s channel networks. The measured channel width, basin length and width, and drainage area all behaved predictably as resolution varied, leading us to conclude that these metrics could be applied to Cassini data. We then mapped all observable fluvial features on Titan—excluding those in the highly incised labyrinth terrains—visible in the Cassini data set. In our new maps, we observe differences in basin shapes between Titan’s polar and equatorial regions and dichotomies in the relative channel density between the northern and southern midlatitudes and poles of Titan: channels are concentrated at the poles and southern midlatitudes. These patterns may reflect differences in bedrock material and/or different climate histories.
... topographic relationship (based on SARTopo and DTMs data, where available), internal texture, and contact relations Williams et al., 2011). In compliance with the guidelines given by Elachi et al. (2004), Farr (1993), and Stofan et al. (2008), Titan's SAR dataset has been interpreted considering SAR's backscatter coefficient σ 0 values (range in linear scale: 0.1 σ 0 ∼1.5; classified as "high": ∼1 σ 0 ∼1.5, "medium": ∼0.5 σ 0 ∼1, "low": ∼0.1 σ 0 ∼0.5, or "variable"), which depend on local incidence angle, surface roughness, volume scattering, and dielectric properties (Cook-Hallett et al., 2015;Elachi et al., 2004;Farr , 1993;Lopes et al., 2010;Malaska et al., 2016b;Williams et al., 2011). A network of linear features interpreted as fluvial valleys (Section 3.1.8) ...
... The overall morphology of this unit is distinctive of ridges eroded by the exogenous agents, whose action results in the typical rugged and dissected, crenulated SAR texture (Radebaugh et al., 2007). Considering the unambiguous theoretical and observational constraints, similar interpretations have been given by previous geomorphological studies on different regions of Titan Lopes et al., 2010;Malaska et al., 2016b;Williams et al., 2011). ...
... The main discriminant between the two units is a relatively well-distributed and homogenous "grainy" texture of the DHU. The analysis of topographic data has shown how the DHU elevation is variable but generally high ( The DHU is interpreted as the result of the erosional breakdown of mountainous terrains, mainly by fluvial erosion and flank deposition Lopes et al., 2010). These processes produce SAR brightness variations (i.e., the "grainy" texture previously mentioned), which are likely dominated by changes in surface roughness, volume scattering, and compositional variations. ...
Evidence for tectonic activity on Titan is provided by the presence of eroded mountain ranges. Xanadu is an equatorial region of Titan characterized by a complex topography, even though, overall, it has a lower average elevation compared to its surroundings. We investigated Xanadu's southwestern margin, a part of the region composed of heavily eroded and rugged terrains to the north and east, and of smoother, more uniform terrains to the west and south. The central portions of southwestern Xanadu (SW Xanadu) are characterized by an extensive fluvial network. The presence of such a distinctive feature was the main reason motivating the study of this area, given its potential to provide tectonic indications. Through detailed geomorphological mapping (map scale 1:700,000) on Synthetic Aperture Radar data and analysis of both fluvial drainage patterns and Digital Terrain Models, we identified several putative tectonic structures in this area: normal faulting to the west and east, thrust faulting to the north, and small‐scale strike‐slip faulting in its central parts. Pull‐apart basins are depressions bounded by both dip‐slip faults and by (overlapping and/or bending) segments of a major transcurrent fault, i.e., they are basins generated in transtensional tectonic settings. We propose that central SW Xanadu is a pull‐apart basin, bordered by both normal and thrust faults and formed by transtensional tectonics, which we consider to be the most recent tectonic phase active in this area. This basin is characterized by small‐scale strike‐slip faulting within it, on which a fluvial network has subsequently imposed.
... Furthermore, satellite RS has the advantage of being able to analyze less accessible dune regions and/or regions with extreme climatic conditions that may restrict field surveys. This even includes extraterrestrial dune systems, such as those on Mars [17] or in the equatorial regions of Titan [18][19][20][21][22][23]. ...
This work presents an automatic procedure to quantify dune dynamics on isolated barchan dunes exploiting Synthetic Aperture RADAR satellite data. We use C-band datasets, allowing the multi-temporal analysis of dune dynamics in two study areas, one located between the Western Sahara and Mauritania and the second one located in the South Rayan dune field in Egypt. Our method uses an adaptive parametric thresholding algorithm and common geospatial operations. A quantitative dune dynamics analysis is also performed. We have measured dune migration rates of 2-6 m/year in the NNW-SSE direction and 11-20 m/year NNE-SSW for the South Rayan and West-Sahara dune fields, respectively. To validate our results, we have manually tracked several dunes per study area using Google Earth imagery. Results from both automatic and manual approaches are consistent. Finally, we discuss the advantages and limitations of the approach presented.
... However, these processes will probably still generate fewer materials than atmospheric photochemistry for acetylene, making ammonia the limiting constituent with respect to forming the acetylene-ammonia co-crystal on Titan. If one were to combine the total surface area of all the strongest candidates for cryovolcanic features (Lopes et al., 2007(Lopes et al., , 2010(Lopes et al., , 2013 with the 73 000 km 2 area identified as a possible ammonia frost deposit (Nelson et al., 2009) located at Hotei Regio (26 S, 78 W) in the enigmatic Xanadu region on Titan, and assume that all of these regions were exposed to acetylene, it is possible that the acetylene-ammonia co-crystal could be Rietveld refinements of the experimental patterns at (a) 85 K and (b) 120 K, collected at = 1.5406 Å . ...
Acetylene and ammonia are known to form a stable orthorhombic co-crystal under the surface conditions of Saturn's moon Titan (1.5 bar = 150 kPa, 94 K). Such a material represents a potential new class of organic minerals that could play an important role in Titan's geology. In this work, the thermal expansion of this co-crystalline system has been derived from in situ powder X-ray diffraction data obtained between 85 and 120 K. The results indicate significant anisotropy, with the majority of the expansion occurring along the c axis (∼2% over the temperature range of interest). Rietveld refinements reveal little change to the structure compared with that previously reported by Boese, Bläser & Jansen [ J. Am. Chem. Soc. (2009), 131 , 2104–2106]. The expansion is consistent with the alignment of C—H...N interactions along the chains in the a and b axes, and weak intermolecular bonding in the structural layers along the c axis.
... The Cassini-Huygens mission gave rise to a much more comprehensive understanding of the Saturnian system [1,2], confirming Titan, Saturn's largest moon, as unique in the Solar System for sustaining a nitrogenbased organically rich atmosphere [3,4], a highly active surface at which complex geological processes occur [5] and a subsurface ocean [6,7]. ...
... A multi-phase alcanological * cycle is present, active across the surface of the body, which includes hydrocarbon lakes and seas primarily clustered around Titan's northern pole [8,9], as seen in Fig. 1. This makes Titan the only location in the Solar System other than Earth to have bodies of liquid on the surface and when considered alongside the presence of organically-rich dunes [10], aeolian activity [11], fluvial features [5] and cryovolcanic activity [12], Titan can be seen as analogous to the early Earth, and so is naturally of interest to abiogenetic studies. ...
Key questions surrounding the origin and evolution of Titan and the Saturnian system in which it resides remain following the Cassini-Huygens mission. In-situ measurements performed at key locations on the body are a highly effective way to address these questions, and the aerial-aquatic platform proposed in this report serves to deliver unprecedented access to Titan's northern surface lakes, allowing an understanding of the hydrocarbon cycle, the potential for habitability in the environment and the chemical processes that occur at the surface. The proposed heavier-than-air flight and plunge-diving aquatic landing spacecraft, ASTrAEUS, is supported by the modelling of the conditions which can be expected on Titan's surface lakes using multiphysics fluid-structure interaction (FSI) CFD simulations with a coupled meshfree smoothed-particle hydrodynamics (SPH) and finite element method (FEM) approach in LS-DYNA.
... The Cassini-Huygens mission gave rise to a much more comprehensive understanding of the Saturnian system [1,2], confirming Titan, Saturn's largest moon, as unique in the Solar System for sustaining a nitrogenbased organically rich atmosphere [3,4], a highly active surface at which complex geological processes occur [5] and a subsurface ocean [6,7]. ...
... A multi-phase alcanological * cycle is present, active across the surface of the body, which includes hydrocarbon lakes and seas primarily clustered around Titan's northern pole [8,9], as seen in Fig. 1. This makes Titan the only location in the Solar System other than Earth to have bodies of liquid on the surface and when considered alongside the presence of organically-rich dunes [10], aeolian activity [11], fluvial features [5] and cryovolcanic activity [12], Titan can be seen as analogous to the early Earth, and so is naturally of interest to abiogenetic studies. ...
Key questions surrounding the origin and evolution of Titan and the Saturnian system in which it resides remain following the Cassini-Huygens mission. In-situ measurements performed at key locations on the body are a highly effective way to address these questions, and the aerial-aquatic platform proposed in this report serves to deliver unprecedented access to Titan's northern surface lakes, allowing an understanding of the hydrocarbon cycle, the potential for habitability in the environment and the chemical processes that occur at the surface. The proposed heavier-than-air flight and plunge-diving aquatic landing spacecraft, ASTrAEUS, is supported by the modelling of the conditions which can be expected on Titan's surface lakes using multiphysics fluid-structure interaction (FSI) CFD simulations with a coupled meshfree smoothed-particle hydrodynamics (SPH) and finite element method (FEM) approach in LS-DYNA.
