Still flowing: the fluvial structures of the Prow outcrop in the arid lower sulfate unit of Gale crater (Mars)
Résumé
The Curiosity rover of the Mars Science Laboratory has been exploring Gale crater since landing in August 2012. Along its ~30 km journey, the rover has encountered sediment rocks deposited in aeolian, lacustrine, but also fluvial settings, evidence of flowing liquid water in the Gale crater around 3.6 Ga. From mid-2021, the rover has been exploring the Mirador formation, also known as the “sulfate-bearing unit”, due to the previous detection from orbit of the spectral signature for these hydrated minerals. This formation is dominated by fine to medium-grained sandstones deposited within an aeolian setting. However, several outcrops along the rover’s traverse have revealed lens-shaped bodies of structured sandstones, strikingly different from the more regional aeolian deposits they are set within. Among those outcrops stands the Prow, explored by the Curiosity rover between January and February 2022. Using high-resolution images and Digital Outcrop Model reconstructions, we characterize several sets of sedimentary structures such as meter-scale cross-stratification, cm-scale symmetric ripples, and likely climbing ripples. These structures indicate sustained conditions compatible with a fluvial setting. Other observations of muddier drapes favor variations of the local energy of the depositional setting, indicating recurrent intervals of low-energy deposition in-between higher-energy periods. Collectively, these elements characterize a dynamic setting of combined flow and wave action at the time the sediments were deposited, helping us to determine that a fluvial regime have intermittently existed within an overall aeolian setting in the Mirador formation of Gale crater.
| Origine | Fichiers produits par l'(les) auteur(s) |
|---|---|
| Licence |