Age dates of valley network drainage basins and subbasins within Sabae and Arabia Terrae, Mars
Résumé
The precise timing of valley network drainage basin formation is critical to understanding the history of water and climate on Mars. To determine whether there are any variations in ages within separate drainage basins and subbasins that may reflect local or regional variations in climate or resetting from resurfacing (e.g., impact ejecta or lava flows), we dated 27 basins and subbasins in Sabaea and Arabia Terrae. The age-dating basin technique we employed allowed sufficient precision to give accurate ages and shows that fluvial activity within the basins and subbasins ceased at approximately the same time around the Early Hesperian/Late Hesperian transition. Our results support the hypothesis that valley networks formed during a unique "fluvial optimum" that may have shut off gradually because of a global climate change that affected all areas simultaneously on Mars.