Geomorphological map of the South Belet Region of Titan

Schoenfeld, Ashley; Lopes, R. M. C.; Malaska, Michael J.; Solomonidou, Anezina; Williams, D. A.; Birch, Samuel; Hayes, Alexander G.; Corlies, P.; Gall, Alice Le; Janssen, M. A.; Mouëlic, Stéphane Le; Turtle, E. P.; Florence, Meghan; Verlander, T.

doi:10.1016/j.icarus.2021.114516

Cited by 9 publications

(47 citation statements)

References 131 publications

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“…Consequently, the criteria used are based primarily on the terrain's SAR brightness (σ 0 ), its texture (uniform, patterned by dunes or likely hills), and the geomorphological context. This classification remains similar to that used by previous geomorphological maps of Titan's equatorial regions (e.g., Williams et al 2011;Lopes et al 2019;Schoenfeld et al 2021), particularly Malaska et al (2016b), whose map of the Afekan crater region includes the Selk crater area, and Lorenz et al (2021), who mapped the Dragonfly landing site based on SAR, ISS, and VIMS data separately. Herein, we used only six units, defined hereafter and mapped in Figure 2.…”

Section: Mapping the Roisupporting

confidence: 71%

“…Hummocky terrains are radar-bright and uniform in texture. They are often surrounded by dunes that seem to wrap around them, consistent with topographic highs, as indicated in some cases by SARTopo (e.g., Malaska et al 2016b;Schoenfeld et al 2021) and altimetry (Poggiali et al 2019;Lalich et al 2022). 4.…”

Section: Mapping the Roimentioning

confidence: 64%

“…They are likely dune fields or sand sheets: either the sand-free interdune regions are unresolved, or the sand cover is thick enough that the radar cannot detect the underlying bedrock. This unit, which is widespread on Titan and especially in the Belet sand sea, is usually included within the linear dunes unit (Malaska et al 2016b;Schoenfeld et al 2021). The fact that there are no apparent radarbright interdune regions in this unit leads to very low backscatter values, often below the noise floor.…”

Section: Mapping the Roimentioning

confidence: 99%

“…Alternating bright/dark regions perpendicular to the radar look direction are apparent over the Selk crater rim (Figure 8(a)), a feature characteristic of the presence of topography and commonly associated with mountains and crater rims on Titan (Malaska et al 2016b;Schoenfeld et al 2021). Assuming uniform surface properties (composition, roughness, etc.)…”

Section: Rim Topography From Radarclinometrymentioning

confidence: 99%

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Composition, Roughness, and Topography from Radar Backscatter at Selk Crater, the Dragonfly Landing Site

et al. 2022

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The Selk crater region is the future landing site of NASA’s Dragonfly mission to Titan. The region was imaged by the Cassini RADAR at incidence angles from 5° to 72° and at various polarization angles. Using this data set, we mapped six terrain units and assembled a backscatter curve for each, providing normalized backscatter cross section (σ 0) as a function of incidence angle. By fitting these backscatter curves with a sum of a quasi-specular and diffuse terms and evaluating three alternative formulations of the first and two for the second, we extracted the best-fit surface effective dielectric constant, rms slope, and scattering albedo. Although the parameters’ absolute values are model dependent, relative values between terrains indicate real variations in surface properties. The results are consistent with the impact exposing and fracturing a low-loss tangent material such as the water-ice bedrock, which is likely also present in the hummocky terrains and to a lesser degree in the plains and interdune regions. The dunes and dark terrains are composed of smooth, uniform material with low dielectric constant (1.5–2.3 median values for all models) compatible with organic sand. A diffuse single-scattering model enabled independent derivation of the dielectric constant from high-incidence observations, leading to low values (<2) over all terrains, indicating a depolarizing (sub)surface. Finally, radarclinometry revealed lateral variations in rim height, which remains below 300 m along the SARTopo profile but reaches up to 600 m at other locations, hinting at a rim less eroded than previously thought.

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Section: Mapping the Roisupporting

confidence: 71%

Section: Mapping the Roimentioning

confidence: 64%

Section: Mapping the Roimentioning

confidence: 99%

Section: Rim Topography From Radarclinometrymentioning

confidence: 99%

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Composition, Roughness, and Topography from Radar Backscatter at Selk Crater, the Dragonfly Landing Site

et al. 2022

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“…Other potentially karstic features include the equatorial pits (Figures 7e and 7f) found in pitted hummocky terrain, which are small, low‐radar backscatter areas usually between 1 and 6 km in diameter (Adams & Jurdy, 2012; Lopes et al., 2020; Schoenfeld et al., 2021) and located in an icy substrate. In a recent analysis of an area in the south Belet region of Titan, Schoenfeld et al.…”

Section: Processes and Productsmentioning

confidence: 99%

Planetary Caves: A Solar System View of Processes and Products

et al. 2022

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Formation of the Siberian Yamal gas emission crater via accumulation and explosive release of gas within permafrost

Schurmeier,

Brouwer,

Fagents

2023

Permafrost & Periglacial

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The Arctic landscape has experienced many dramatic forms of change due to anthropogenic warming. Large crater‐like forms surrounded by fragmented blocks scattered outward to great distances with precursor mounds appeared in the continuous permafrost zone of the Yamal and Gydan peninsulas of Western Siberia. The morphologies of these craters, in addition to the abundant evidence of active and intense gas emissions across the region, indicate that they formed due the subsurface accumulation, pressurization, and explosive release of gasses trapped within the permafrost. Therefore, these craters were termed “gas emission craters” (GEC). However, some have suggested that in addition to gas accumulation, these features form in a manner similar to ice‐cored pingos and require pressurization due to the freezing of subsurface ice. This is despite the fact that not all GECs form in areas conducive to pingo‐like ice accumulation. Here, we test whether the pressurization and explosive release of methane gas alone can reproduce the observed morphology of the first‐discovered and most intensely studied GEC, Yamal crater. We use the available field and satellite data to constrain the initial dimension parameters of a model of the explosion process and consider several plausible configurations for the unknown interior cavity shape, the overlying permafrost cap thickness, and gas chamber volume. The explosion process is modeled in phases: gas migrates upward and accumulates in the subsurface until the gas pressure fractures the overlying cap, the expanding gas and cap blocks are initially accelerated outward together, and then the blocks are launched as projectiles. The sizes and locations of the ejected blocks found at Yamal crater are used to determine the initial gas pressures required to launch those projectiles to the observed locations. Finally, we estimate the amount of gas released in each of the multiple model runs testing different plausible internal cavity geometries. For the range of plausible block sizes and densities, and a subset of gas chamber volumes considered, we find that the gas pressure (0.6–2.6 MPa) required to launch the Yamal crater blocks to their observed distances was within the range of the sum of the ice/permafrost tensile strength and the lithostatic pressure (0.22–2.87 MPa). Thus, the observed blocks could have been launched by the energy required to fracture and displace the overlying permafrost cap. We show that the mechanism of formation of this GEC does not require pressure from the freezing of ice in the subsurface to crack and explode the overlying permafrost—gas pressure alone can produce these GECs. We expect that as our planet warms, the Siberian permafrost will continue to warm, weaken, and release gasses such as the greenhouse gas methane, and contribute to a permafrost carbon‐positive feedback cycle that would lead to the formation of even more explosive GECs.

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Geomorphological map of the South Belet Region of Titan

Cited by 9 publications

References 131 publications

Composition, Roughness, and Topography from Radar Backscatter at Selk Crater, the Dragonfly Landing Site

Composition, Roughness, and Topography from Radar Backscatter at Selk Crater, the Dragonfly Landing Site

Planetary Caves: A Solar System View of Processes and Products

Formation of the Siberian Yamal gas emission crater via accumulation and explosive release of gas within permafrost

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