Titan's Topography and Shape at the End of the Cassini Mission

Corlies, P.; Hayes, Alexander G.; Birch, Samuel; Lorenz, Ralph D.; Stiles, B.; Kirk, Randolph L.; Poggiali, Valerio; Zebker, H. A.; Iess, L.

doi:10.1002/2017gl075518

Cited by 88 publications

(78 citation statements)

References 37 publications

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“…We determined the remaining cell classifications locally by considering the correlation between VIMS and RADAR units on both the regional and global scale. With grid spacing at least 2 orders of magnitude larger than RADAR resolution, a cell often Corlies et al (2017) for each geomorphological unit. The number of cells has been weighted by the cosine of latitude to account for the polar stretch of the cylindrical projection.…”

Section: Mapping By Terrain Typesmentioning

confidence: 99%

A Thermal Inertia Map of Titan

2019

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Like Earth, the atmosphere of Titan, Saturn's largest moon, is affected by the ability of the surface to store and release heat. Modeling efforts have shown that global temperature distributions and wind profiles differ between simulations describing Titan's surface with a uniform thermal inertia. Cassini‐Huygens demonstrated, however, that a variety of morphologies and compositions make up the Titanian landscape. Using data from Cassini RADAR and the Visible and Infrared Mapping Spectrometer, we classified the surface into five terrain types: dune, lake, hummocky, plains, and labyrinth. We estimated the thermal and physical properties (conductivity, specific heat, and density) for each type, creating a 1° × 1° global map of thermal inertia values. For the lakes, as the depth of convection is not yet known, we considered both still and convective bodies. Four simulations of the Titan Atmospheric Model were run with different surface thermal properties: a low homogeneous thermal inertia, a moderate homogeneous, the heterogeneous map with still lakes, and the heterogeneous map with convective lakes. In dry regimes (i.e., without the hydrological cycle), the differences between the four cases were generally minimal, suggesting that general circulation models can use a single (moderate) value for surface thermal inertia value for large‐scale investigations that do not consider diurnal variations. Given the importance of hydrological processes and regional spatial diversity on Titan, future work should consider the effects of nonuniform thermal inertia on Titan's climate on local and regional scales.

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Section: Mapping By Terrain Typesmentioning

confidence: 99%

A Thermal Inertia Map of Titan

2019

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“…The stability of Titan's tropical lakes in three similar‐sized tropical endorheic basins (Shangri‐La, Western Xanadu and Eastern Xanadu) was investigated by a lake balance model considering the global topography map obtained by Cassini (Corlies et al, ) and meteorological input from author's GCM (Tokano, ). The total volume of liquid methane in an endorheic basin is predicted by solving the equation

\frac{d V}{d t} = \int_{A_{B}} c P d A - \int_{A_{L}} E d A,

where

V

is the total volume of liquid methane,

c

is the runoff coefficient (a value between 0 and 1),

P

is the precipitation rate per unit area,

E

is the evaporation rate from the lake surface per unit area,

A

is the area over which to integrate,

A_{B}

is the constant drainage basin area, and

A_{L}

is the variable lake surface area where

A_{L} < A_{B}

.…”

Section: Methodsmentioning

confidence: 99%

Stable Existence of Tropical Endorheic Lakes on Titan

Tokano

2020

Geophysical Research Letters

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Cassini detected numerous hydrocarbon seas/lakes in the polar region of Titan and wide areas of sand seas in the tropical region, which initially led to the perception that Titan's tropical region may be too dry for lakes. Yet, a few tropical lakes were possibly seen on Cassini's near‐infrared images, while they were not seen by other imaging instruments. This study shows by a lake balance model in combination with a global climate model and global topography map that a few lakes can perennially exist in Titan's tropical drainage basins of Shangri‐La, Tui Regio, and Hotei Regio. This is possible because the lakes are fed by precipitation in a huge catchment area, while efficient lake evaporation occurs only in a small area inside of deep topographic depressions. However, tropical lakes may occasionally desiccate due to orbitally forced changes in tropical precipitation.

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“…In some cases we are still able to resolve rims in SARtopo and DTM data that are smaller than 100 m in elevation. Relative measurements along a single SARtopo swath or along a single DTM can confidently resolve features as small as ∼20 m in elevation (Corlies et al, ). Instead, identification of rims using topographic data is limited by the spatial resolution, not vertical, where we are not able to identify rims smaller than ∼1 km in width, regardless of their height.…”

Section: Rim Identificationmentioning

confidence: 99%

Raised Rims Around Titan's Sharp‐Edged Depressions

Birch

Hayes

Poggiali

et al. 2019

Geophysical Research Letters

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We perform a systematic survey of Titan's sharp‐edged depressions (SEDs) using a combination of Cassini synthetic aperture radar images and delay‐Doppler processed altimetry. We identify a characteristic bright‐dark pattern around 172 SEDs that correlates with elevated features only resolved with the highest resolution topographic data. We find that ∼75% of Titan's SEDs have elevated (∼100 m) rim features, with a preference toward larger SEDs. The differences in the distribution of SED rim presence between the north and south are slight, but the data weakly suggest that northern SEDs may be more likely to have a rim. The pattern we identify in synthetic aperture radar images is similar to quasi‐specular increases in backscatter seen on Titan's dunes. We show that this bright‐dark pattern occurs due to elevated local slopes oriented perpendicular to the radar. In general, rims occur on most of Titan's SEDs, an observation that will aid in developing and testing SED formation models.

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Titan's Topography and Shape at the End of the Cassini Mission

Cited by 88 publications

References 37 publications

A Thermal Inertia Map of Titan

A Thermal Inertia Map of Titan

Stable Existence of Tropical Endorheic Lakes on Titan

Raised Rims Around Titan's Sharp‐Edged Depressions

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