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Communication Dans Un Congrès Année : 2021

The Unexpected Origin of the Branched Ridges at Antoniadi Crater, Mars

Résumé

[1]. The branched ridges lie on these plains and to the south of a 28 km-diameter well-preserved crater devoid of any signs of fluvial erosion (Fig. 2). This crater also predates the branched ridges because the plains material buries its southern ejecta. While some erosion has affected the ridges, there is no indication of exhumation of these ridges from layers below the current plains surface. The crater size frequency distribution of the plains gives a model age of 2.5±0.5 Gy, using diameters of 200 m to 2 km. Thus, the branched ridges are Early Amazonian or younger, adding to their interest if they formed by fluvial activity. Morphology: The branched ridges show a suite of peculiar morphological characteristics. Their texture at HiRISE scale (25cm/pixel) is rubbly with the occurrence of blocks up to ~1 m in size and a complete lack of layering (Fig. 3) in all 5 HiRISE images where they are present. The branched ridges appear darker than the plains on which they lie. The ridges are organized as a dendritic network reaching a Strahler order of 4, i.e. the degree of hierarchy from the shortest branches (of order 1) counting the number of junctions. Assuming tributary flows, this organization indicates a northward flow direction. Ridges are up to 10 km long and 10-200 m wide without any obvious trends in width, i.e. ridges are not wider with increasing Strahler order. The order 1 branches are also peculiar in plan-view shape. They frequently display lobate shapes and are up to 100 m wide, which is wider than the ridge measured after the junction with several order 1 branches (r1 in Fig. 3).
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Dates et versions

hal-03452460 , version 1 (26-11-2021)

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  • HAL Id : hal-03452460 , version 1

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Nicolas Mangold, L Tornabene, Susan J. Conway, A Guimpier, Axel Noblet, et al.. The Unexpected Origin of the Branched Ridges at Antoniadi Crater, Mars. 52nd Lunar and Planetary Science Conference, Mar 2021, held virtually, United States. ⟨hal-03452460⟩
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