Sand Sea Research Articles

A prospectus for future geomorphological investigation of the Namib Sand Sea

The Namib Sand Sea in southern Africa offers an ideal location in which to consider general questions about the evolution of sand seas, about the fluxes of sand through contemporary dune fields and about the patterns of dune form that are created. This paper aims to provide a concise account of the approaches and techniques that are currently being used and will be used in the future to address these questions. The paper considers the techniques employed to investigate wind climate, the morphometry of the dunes, the internal structure of dune sediments, the age of the dunes and the potential to model dune development.

Two modes for dune orientation

Research Article| September 01, 2014 Two modes for dune orientation Sylvain Courrech du Pont; Sylvain Courrech du Pont * 1Laboratoire Matière et Systèmes Complexes, Sorbonne Paris Cité, Université Paris Diderot, CNRS UMR 7057, 10 rue A. Domon et L. Duquet, 75205 Paris Cedex13, France *E-mail: sylvain.courrech@univ-paris-diderot.fr. Search for other works by this author on: GSW Google Scholar Clément Narteau; Clément Narteau 2Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, CNRS UMR 7154, 1 rue Jussieu, 75238 Paris Cedex 05, France Search for other works by this author on: GSW Google Scholar Xin Gao Xin Gao 2Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, CNRS UMR 7154, 1 rue Jussieu, 75238 Paris Cedex 05, France Search for other works by this author on: GSW Google Scholar Geology (2014) 42 (9): 743–746. https://doi.org/10.1130/G35657.1 Article history received: 08 Mar 2014 rev-recd: 03 Jun 2014 accepted: 04 Jun 2014 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Sylvain Courrech du Pont, Clément Narteau, Xin Gao; Two modes for dune orientation. Geology 2014;; 42 (9): 743–746. doi: https://doi.org/10.1130/G35657.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Earth’s sand seas (dune fields) experience winds that blow with different strengths and from different directions in line with the seasons. In response, dune fields show a rich variety of shapes, from crescentic barchans to star and linear dunes. These dunes commonly exhibit complex and compound patterns with a range of length scales and various orientations, which up to now have remained difficult to relate to wind cycles. Here, we develop a model for dune orientation that explains the coexistence of bedforms with different alignments in multidirectional wind regimes. This model derives from subaqueous experiments, which show that a single bidirectional flow regime can lead to two different dune orientations depending on sediment availability, i.e., the erodibility of the bed. Sediment availability selects the overriding mechanism for the formation of dunes: increasing in height from the destabilization of a sand bed (with no restriction in sediment availability) or elongating in a finger on a non-erodible surface from a localized sand source. These mechanisms drive the dune orientation. Therefore, dune alignment maximizes dune orthogonality to sand fluxes in the bed instability mode, while dunes are aligned with the mean sand transport direction in the fingering mode. Applied to Earth’s deserts, the model quantitatively predicts the orientation of rectilinear dunes and their superimposed patterns. This field study suggests that many linear dunes on Earth elongate from sources, and are simply aligned with the mean sand transport direction. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Source provenance of carbonate grains in the Wahiba Sand Sea, Oman, using a new LIBS method

The Wahiba Sand Sea is a large dune system composed of northern and southern zones. The dunes receive sand from multiple sources including two fluvial systems draining mountain basins, older underlying dunes, and a large coastline. Although the sand sea is distinctly divided into geomorphic regions with different dunes types, ages, and bulk mineral compositions, the ubiquitous presence of carbonate grains throughout the dune field has led to models that suggest the coast and shallow shelf is the direct and primary source of sediment for the entire sand sea. This study uses a novel method which couples selective, grain-by-grain analysis using laser-induced breakdown spectroscopy (LIBS) of a single mineral species with the classification method of Soft Independent Modeling of Class Analogy (SIMCA). The analysis of carbonate grains using the LIBS method reveals that the carbonates are comprised of several sub-populations that are well mixed throughout the dune field. Individual sources of carbonate grains are also composed of multiple sub-populations creating further complexity. Sand in the Northern Wahiba is predominantly, and directly, derived from wadi systems that lie on the west and northeast sides of the dunes and once bordered the southern end of the dunes. The Southern Wahiba is composed of a more complex mixture of sand derived from the coast; however, the coastal sediments themselves were dominantly derived from the fluvial systems in the region, along with sediment of unknown original source. The new LIBS/SIMCA method of grain-by-grain analysis shows promise for unraveling complex mixing patterns in sedimentary deposits.

Dune systems of the Namib Desert – a spatial and temporal perspective

Aeolian processes have operated in the Namib Desert for much of the past 15 Ma in apparently similar boundary conditions of wind regime and sediment supply, leading to accumulation of dune fields and sand seas, the extent and characteristics of which reflect regional variations in accommodation space, wind regime and sediment supply.

External supply of dust in the Taklamakan sand sea, Northwest China, reveals the dust-forming processes of the modern sand sea surface

As one of the most important global dust sources, the sand sea and neighboring areas contain multiple types of surfaces that release dust, such as dry lakes and riverbeds, degraded oases, and Gobi surfaces. To understand the link between those active sources of dust and the dust formation process of the sand sea surface, we investigated dust fallout characteristics at a height of 3m and rare earth element (REE) geochemistry of different landforms in the Taklamakan sand sea, which has frequent dust events. The seasonal fallout and concentrations of PM10 particles and monitoring results of their land surface concentrations show that the Taklamakan sand sea is surrounded by dust sources, and it's an important dust deposit area. The particle size characteristics of dust sediment suggest that the dust-conveying capacity of the Taklamakan sand sea is much stronger than that of the Gobi and degraded surfaces on the sand sea edge. During sand/dust storms, the fine dust fraction (<40μm) can frequently recycle between the Taklamakan sand sea and the active dust emission areas. Chondrite-normalized REE patterns and Eu/Eu* vs. La CH/Yb CH and (La/Yb)CH vs. LaCH ratios of land surface PM10 fraction and dust PM10 fractions further suggest that there are two types of cycle processes for fine dust particles (<40μm) between the Taklamakan sand sea and surrounding Gobi and degraded land. First, multiple large scale sand/dust storms have occurred between the Taklamakan sand sea and surrounding Gobi and degraded land over a long historical period. This has caused the fine fractions of land surface sediment to be strongly mixed over the entire Tarim Basin, and the geochemical characteristics of the land surface PM10 fractions have strong homogeneity. Second, a localized and seasonal sand/dust storms has released an abundance of fine dust particles from the surrounding area. These have been mixed and deposited in the Taklamakan sand sea under the dominant wind force, and most particulate material are probably also reworked by the wind as the sand saltates and the dunes migrate, resulting in REE concentrations of the dust PM10 fraction that are much higher than those from the surrounding areas.

The formation of the Namib Sand Sea inferred from the spatial pattern of magnetic rock fragments

The Namib Sand Sea on the west coast of Namibia is one of the world's oldest desert region and based on cosmogenic dating it has likely existed since the earlier Pleistocene. Among the possible sand sources, geomorphological and petrographic evidence points towards the Orange River catchment as the most prominent one. Little is known about the dynamics of transport and mixing of the sand during the desert formation and this is because the information about the Namib Sand Sea generally rests upon study sites at its edges. Here, we present a statistical analysis of magnetic components in sand samples collected along a south to north transect through the desert and at two inland sites. The magnetic components are rock fragments mainly of basaltic origin. Their statistically uniform distribution in the Namib Sand Sea indicates no significant sand source other than the Orange River and thus a predominant northward direction of the sand transport. A northward transport and the absence of a magnetic trend along the transect suggests mixing of the sand prior to its deposition in the Namib Sand Sea, most likely during river transport and under high current conditions along the shoreline. Finally, the uniform magnetic pattern provides compelling evidence for a stable erosion regime in the Orange River catchment with a steady release of magnetic components at least since the Pleistocene.

Near-infrared spectra of ferrous mineral mixtures and methods for their identification in planetary surface spectra

Iron-bearing minerals are a major component of planetary surfaces, and many can be identified by their characteristic absorption bands in the near-infrared (NIR). Here we present laboratory NIR spectra of a wide range of common Fe-bearing minerals (e.g., olivines, pyroxenes), glasses, and mineral/glass mixtures. We then use this suite of spectra to evaluate the effects of mixtures on mineral detection methods, including olivine and pyroxene spectral indices developed for the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) onboard Mars Reconnaissance Orbiter. We find that although these indices can be compromised by minerals with atypical compositions, mineral mixtures, and the presence of other ferrous minerals, these issues can generally be mitigated by visual inspection of the spectra. However, a special case occurs when the mineral or mixture in question is spectrally indistinguishable from a more common mineral. In particular, we show that spectra of high-calcium pyroxene mixed with Fe-bearing glass can be virtually indistinguishable from common Fe-bearing olivine compositions. This effect, combined with the fact that Fe-bearing glass is generally much more difficult to detect than other ferrous minerals, may be causing glass occurrences on planetary surfaces to be underreported. In support of this hypothesis, we use Mars Express OMEGA observations to show that previous olivine detections in the north polar sand sea on Mars are actually more consistent with local mixing of glass and pyroxene. To address these issues, we present an alternative ferrous mineral identification method based on the position and shape of the 1 and 2μm iron absorption bands, which are sensitive to mineralogy, composition, and mineral mixtures in planetary surface spectra, including glass and mixtures with glass. Using Chandrayaan-1 Moon Mineralogy Mapper (M3) observations of Aristarchus Crater on the Moon, we show that these band parameters can reveal subtle spectral variations and can produce mineralogical maps at an exceptional level of detail.

Recent advances in research on the aeolian geomorphology of China's Kumtagh Sand Sea

Abstract. The Kumtagh Sand Sea in the hyper-arid region of northwestern China remained largely unexplored until the last decade. It deserves study due to its significance in understanding the evolution of the arid environments in northwestern China, and even central Asia. Aeolian geomorphology in the sand sea has received unprecedented study in the last decade. Encouraging advances have been made in types of aeolian landforms, geological outlines, wind systems, the formation of aeolian landforms, several unique aeolian landforms, aeolian geomorphic regionalization, aeolian geomorphological heritages and tourism development, and aeolian sand hazards and their control. These advances expand our knowledge of aeolian geomorphology.

Aeolian sorting processes in the Ejina desert basin (China) and their response to depositional environment

Granulometric analysis of Aeolian and fluvial sediments in a middle-latitude desert basin (Ejina) was conducted. Sediments were collected from four main geomorphological units (Gobi/foredune, interdune, dune crest and riverbed) which represent the typical surficial conditions. Dunes studied are relatively coarser and lie towards the worse-sorted end of the range in comparison with other deserts. Both the M-z values of aeolian and fluvial sediments tend to decrease as the distance increase toward the Langxin-shan but in different variational patterns for sorting parameters between them, indicating a regular change of grain size but different sorting processes in the regional scale between Aeolian and fluvial sediments. Dune sands become finer and better sorted and less positively skewed from dune crest to interdune and foredune. This sorting pattern in dune unit appears to follow those described from the Libya and Namib deserts. While, the Ejina dunefield is located close to its sand sources, which for the most part are believed in this study to be distal palaeo-alluvial fan deposits (Gobi sediments) rather than modern fluvial sediments. The Ejina dunes therefore contain significant amounts of coarse grains with weak sorting degree. This is unlike so-called mature sand seas (e.g., central Namib Sand Sea), which lie at some distance in time and space from the original sources of sediment, indicating that the availability of particle sizes in source area exerts a strong influence on the spatial patterns of particle size and sorting in the Ejina dunes. (C) 2013 Elsevier B.V. All rights reserved.

Libyan Desert Glass: New field and Fourier transform infrared data

AbstractResults are presented of new geological observations and laboratory analyses on Libyan Desert Glass (LDG), a unique kind of impact glass found in Egypt, probably 28.5–29.4 million years in age. A new LDG occurrence has been discovered some 50 km southward of the main LDG occurrences in the Great Sand Sea. From Fourier transform infrared (FTIR) analysis, the molecular structure of LDG is refined and significant differences are shown between LDG specimens and other pure silica glasses (fulgurite, industrial fused quartz, and amorphous biogenic silica) that are related to differences in their structures. The slight variations observed here for the mean Si‐O‐Si angle between the different glasses are attributed to their thermal histories. With regard to the other glasses analyzed, the LDG infrared spectral parameters point to a higher ratio of discontinuities and defects in the tetrahedral (SiO4) network. The quantitative mineralogical constitutions of sandstones and quartzites from the LDG geological setting were analyzed by FTIR. Cretaceous sandstones have a specific composition (about 90 wt% quartz, 10% dickite), clearly different from the Paleozoic ones (about 90 wt% quartz, but ≥7% kaolinite). It is shown that the reddish silts bearing the LDG are constituted mainly of microquartz enriched with dickite, whose particle size distribution is characteristic of fluvio‐lacustrine deposits, probably Oligocene to Miocene in age. The target rocks, most probably quartz sand, resulted from the weathering (loss of the cementing microquartz) of the Cretaceous sandstones from the Gilf Khebir Plateau with deposition in a high‐energy environment.

The surface geology and geomorphology around gobabeb, namib desert, namibia

This paper serves as a brief review and overview of the surface geology and geomorphology around obabeb in the entral amib esert. It introduces the major lithologies associated with the amara rogen of Precambrian and ambrian age, followed by ertiary sandstones and conglomerates and uaternary uiseb valley conglomerates, silts and gravels. To celebrate the 50th anniversary of the obabeb research station and the recent designation of the amib and ea as a world heritage site, we are presenting a map to inform and guide future research and educational activities around obabeb. The contrast between an ancient gravel plain to the north, a dynamic aeolian sand sea to the south and ephemeral river environments in between become apparent. These natural laboratories have attracted investigations of contemporary sand dune movement, hyper saline waters, evaporites and duricrusts and ephemeral flooding and recharge processes as well as environmental change and human impacts.

Helga's dune: 40 years of dune dynamics in the namib desert

The dynamics of a small linear dune on the northern margin of the Namib Sand Sea have been monitored using erosion pins placed at the dune tip since 1969. measurements of these pins enabled estimation of the rates of advance and lateral migration of the dune. The average rate of advance of the dune tip over the period 1969–2012 was 1.99 m yr–1 towards 015°. Rates of advance and lateral movement varied over the period of monitoring, with a decrease in rates of advance by a factor of 50%, but an increase in the rate of lateral movement. Changes in dune behavior appear to be related to changes in wind regime and the vegetation cover of the interdune area, as a result of increased rainfall in recent years. This study demonstrates the dynamic nature of the tip of this dune and its sensitivity to changes in winds and sand supply.

Titan dune heights retrieval by using Cassini Radar Altimeter

The Cassini Radar is a Ku band multimode instrument capable of providing topographic and mapping information. During several of the 93 Titan fly-bys performed by Cassini, the radar collected a large amount of data observing many dune fields in multiple modes such as SAR, Altimeter, Scatterometer and Radiometer. Understanding dune characteristics, such as shape and height, will reveal important clues on Titan’s climatic and geological history providing a better understanding of aeolian processes on Earth. Dunes are believed to be sculpted by the action of the wind, weak at the surface but still able to activate the process of sand-sized particle transport. This work aims to estimate dunes height by modeling the shape of the real Cassini Radar Altimeter echoes. Joint processing of SAR/Altimeter data has been adopted to localize the altimeter footprints overlapping dune fields excluding non-dune features. The height of the dunes was estimated by applying Maximum Likelihood Estimation along with a non-coherent electromagnetic (EM) echo model, thus comparing the real averaged waveform with the theoretical curves. Such analysis has been performed over the Fensal dune field observed during the T30 flyby (May 2007). As a result we found that the estimated dunes’ peak to trough heights difference was in the order of 60–120m. Estimation accuracy and robustness of the MLE for different complex scenarios was assessed via radar simulations and Monte-Carlo approach. We simulated dunes–interdunes different composition and roughness for a large set of values verifying that, in the range of possible Titan environment conditions, these two surface parameters have weak effects on our estimates of standard dune heights deviation.Results presented here are the first part of a study that will cover all Titan’s sand seas.

Implications of dune pattern analysis for Titan’s surface history

Analysis of large-scale morphological parameters can reveal the reaction of dunes to changes in atmospheric and sedimentary conditions. Over 7000 dune width and 7000 dune spacing measurements were obtained for linear dunes in regions across Saturn’s moon Titan from images T21, T23, T28, T44 and T48 collected by the Synthetic Aperture RADAR (SAR) aboard the Cassini spacecraft in order to reconstruct the aeolian surface history of Titan. Dunes in the five study areas are all linear in form, with a mean width of 1.3km and mean crest spacing of 2.7km, similar to dunes in the African Saharan and Namib deserts on Earth. At the resolution of Cassini SAR, the dunes have the morphology of large linear dunes, and they lack evidence for features of compound or complex dunes. The large size, spacing and uniform morphology are all indicators that Titan’s dunes are mature features, in that they have grown toward a steady state for a long period of time. Dune width decreases to the north, perhaps from increased sediment stabilization caused by a net transport of moisture from south to north, or from increased maturity in dunes to the south. Cumulative probability plots of dune parameters measured at different locations across Titan indicate there is a single population of intermediate-to-large-sized dunes on Titan. This suggests that, unlike analogous dunes in the Namib and Agneitir Sand Seas, dune-forming conditions that generated the current set of dunes were stable and active long enough to erase any evidence of past conditions.

Dunes on Saturn’s moon Titan as revealed by the Cassini Mission

Dunes on Titan, a dominant landform comprising at least 15% of the surface, represent the end product of many physical processes acting in alien conditions. Winds in a nitrogen-rich atmosphere with Earth-like pressure transport sand that is likely to have been derived from complex organics produced in the atmosphere. These sands then accumulate into large, planet-encircling sand seas concentrated near the equator. Dunes on Titan are predominantly linear and similar in size and form to the large linear dunes of the Namib, Arabian and Saharan sand seas. They likely formed from wide bimodal winds and appear to undergo average sand transport to the east. Their singular form across the satellite indicates Titan’s dunes may be highly mature, and may reside in a condition of stability that permitted their growth and evolution over long time scales. The dunes are among the youngest surface features, as even river channels do not cut through them. However, reorganization time scales of large linear dunes on Titan are likely tens of thousands of years. Thus, Titan’s dune forms may be long-lived and yet be actively undergoing sand transport. This work is a summary of research on dunes on Titan after the Cassini Prime and Equinox Missions (2004–2010) and now during the Solstice Mission (to end in 2017). It discusses results of Cassini data analysis and modeling of conditions on Titan and it draws comparisons with observations and models of linear dune formation and evolution on Earth.

Remote sensing of spatial variability in aeolian dune and interdune morphology in the Rub’ Al-Khali, Saudi Arabia

The Rub' Al-Khali aeolian sand sea of south eastern Saudi Arabia - also known as the Empty Quarter - covers an area of 660,000 km and is one of the largest sandy deserts in the world. The region is covered by the latest generation of public-release satellite imagery, which reveal spatially diverse dune patterns characterized by a varied range of dune types, the morphology, scale and orientation of which change systematically from central to marginal dune-field areas where non-aeolian sub-environments become dominant within the overall desert setting. Analysis of geomorphic relationships between dune and interdune sub-environments within 4 regions of the Rub' Al-Khali reveals predictable spatial changes in dune and interdune morphology, scale and orientation from the centre to the outer margins of dune fields. A quantitative approach is used to characterize the complexity present where large, morphologically complex and compound bedforms gradually give way to smaller and simpler bedform types at dune-field margins. Parameters describing bedform height, spacing, parent morphological type, bedform orientation, lee-slope expression, and wavelength and amplitude of along-crest sinuosity are recorded in a relational database, along with parameters describing interdune size (long- and short-axis dimensions), orientation, and style of connectivity. The spatial rate of change of morphology of aeolian sub-environments is described through a series of empirical relationships. Spatial changes in dune and interdune morphology have enabled the development of a model with which to propose an improved understanding of the sediment system state of the modern Rub' Al-Khali desert sedimentary system, whereby the generation of an aeolian sediment supply, its availability for aeolian transport and the sand transporting capacity of the wind are each reduced in dune-field margin areas.

A new high‐resolution central and western Saharan summertime dust source map from automated satellite dust plume tracking

AbstractIn this paper, we outline a new objective dust source detection method for the central and western Sahara (CWS), based on the automated tracking of individual dust plumes in data from the Spinning Enhanced Visible and Infrared Imager, available every 15 mins. at ~0.03° spatial resolution. The method is used to map the origin of summertime dust storms in the CWS for June – August 2004 – 2010. It reveals the sources of these events in unprecedented detail, allowing for the identification of specific, highly active source areas. The study of collocated surface features reveals that many of the dominant sources are likely associated with paleolakes and outwash plains, many in close proximity to the Saharan mountains. Extensive nonsource areas are associated with low albedo and elevated terrain, pointing to the mountainous regions of the Sahara. Additionally, sand seas are not identified as important source areas, but their margins sometimes are. The automated tracking method also facilitates analysis of the transport direction of dust plumes from key source regions and the inference of emission mechanisms. It is found that there are two broad domains within the CWS: one in southwest Algeria and northwest Mali, characterized primarily by transport toward the southwest and very likely dominated by low‐level jets embedded in the northeasterly Harmattan winds; and a second in southern Algeria, northwest Niger, and northeast Mali where there is no preferred transport direction and a strong potential association between dust events and deep convection, pointing toward cold pool outflows as the likely deflation mechanism.

Dune types and their distribution in the Kumtagh Sand Sea, northwestern China

Integrated regional studies are important tools for understanding dune geomorphology. As a part of an integrated regional study of dune geomorphology in the Kumtagh Sand Sea, northwestern China, we described the dune types and their distribution. In this paper, we propose a tentative dune classification scheme for these dunes based on previous schemes. We identified 11 main types of dunes, described their distribution, and estimated the areas they covered. Dunes generally became more complex moving from the north to the south of the study area, and from the edges to the inner areas of the sand sea. The wind regime also became more complex moving towards the south due to the physical blocking and thermodynamic effects of the mountains and the Qinghai-Tibetan Plateau, as well as the increasingly complex underlying topography. The combination of these factors appears to be responsible for the observed spatial variation of the dune types. Dune heights were estimated from 1:100,000 topographic maps and remote-sensing images. More than 80% of the dunes in the Kumtagh Sand Sea were less than 100 m tall, but with a maximum height exceeding 300 m. Dune height increased from north to south, with the tallest dunes occurring near the southern mountains. This general distribution of dune heights suggests that dune height was determined by a combination of sediment availability, airflow patterns, the blocking effect of mountains, and the underlying topography.

Holocene footprints in Namibia: The influence of substrate on footprint variability

We report a Holocene human and animal footprint site from the Namib Sand Sea, south of Walvis Bay, Namibia. Using these data, we explore intratrail footprint variability associated with small variations in substrate properties using a "whole foot" analytical technique developed for the studies in human ichnology. We demonstrate high levels of intratrail variability as a result of variations in grain size, depositional moisture content, and the degree of sediment disturbance, all of which determine the bearing capacity of the substrate. The two principal trails were examined, which had consistent stride and step lengths, and as such variations in print typology were primarily controlled by substrate rather than locomotor mechanics. Footprint typology varies with bearing capacity such that firm substrates show limited impressions associated with areas of peak plantar pressure, whereas softer substrates are associated with deep prints with narrow heels and reduced medial longitudinal arches. Substrates of medium bearing capacity give displacement rims and proximal movement of sediment, which obscures the true form of the medial longitudinal arch. A simple conceptual model is offered which summarizes these conclusions and is presented as a basis for further investigation into the control of substrate on footprint typology. The method, model, and results presented here are essential in the interpretation of any sites of greater paleoanthropological significance, such as recently reported from Ileret (1.5 Ma, Kenya; Bennett et al.: Science 323 (2009) 1197-1201).

Modeling the SAR backscatter of linear dunes on Earth and Titan

We modeled the Synthetic Aperture Radar (SAR) response of linear dunes of the Great Sand Sea in Egypt using a single surface scattering term, based on Integral Equation and Physical Optics Models. Using multi-frequency SIR-C/X-SAR radar scenes and topography obtained from the Shuttle Radar Topography Mission (SRTM), we were able to estimate reasonable values for the parameters describing the surface roughness of the dunes. As the linear dunes of the Great Sand Sea are relevant analogs for the linear dunes observed on Titan by the Cassini Radar instrument, these results were thus used as a starting point to simulate the radar response of Titan’s dunes, as imaged by the Radar instrument onboard the Cassini spacecraft during the T8 flyby in October 2005. We show that a single surface scattering term is not sufficient to simulate the radar signal backscattered by the dunes on Titan: one has to add a diffuse scattering term, indicating that Titan’s dunes are likely to have somewhat inhomogeneous internal structures related to porosity and/or internal layering. Our results also indicate that the dunes on Titan should be close to perfectly smooth, possibly because of the formation of smaller ripples than on Earth, plus smoothing resulting from precipitation events.