Dune fields on Titan cover more than 17% of the moon's surface, constituting the largest known surface reservoir of organics. Their confinement to the equatorial belt, shape, and eastward direction of propagation offer crucial information regarding both the wind regime and sediment supply. Herein, we present a comprehensive analysis of Titan's dune orientations using automated detection techniques on nonlocal denoised radar images. By coupling a new dune growth mechanism with wind fields generated by climate modeling, we find that Titan's dunes grow by sediment transport on a nonmobile substratum. To be fully consistent with both the local crestline orientations and the eastward propagation of Titan's dunes, the sediment should be predominantly transported by strong eastward winds, most likely generated by equinoctial storms or occasional fast westerly gusts. Additionally, convergence of the meridional transport predicted in models can explain why Titan's dunes are confined within ±30• latitudes, where sediment fluxes converge.

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Estimates of the Martian elastic lithosphere thickness suggest small values of ∼25 km during the Noachian for the southern hemisphere and a large present‐day difference below the two polar caps (≥300 km in the north and >110 km in the south). In addition, young lava flows suggest that Mars has been volcanically active up to the recent past. We run Monte Carlo simulations using a 1‐D parameterized thermal evolution model to investigate whether a north/south hemispheric dichotomy in crustal properties and composition can explain these constraints. Our results suggest that 55–65% of the bulk radioelement content are in the crust, and most of it (43–51%) in the southern one. The southern crust can be up to 480 kg/m3 less dense than the northern one and might contain a nonnegligible proportion of felsic rocks. Our models predict a dry mantle and a wet or dry crustal rheology today. This is consistent with a mantle depleted in radioelements and volatiles. We retrieve north/south surface heat flux of 17.1–19.5 mW/m2 and 24.8–26.5 mW/m2, respectively, and a large difference in lithospheric temperatures between the two hemispheres (170–304 K in the shallow mantle). This difference could leave a signature in the seismic signals measured by the future InSight mission.

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