Reassessing the Ancient Martian Ocean Hypothesis using Global Distribution of Valley Networks

Abstract:

We re-examine the connection between true polar wander and the Martian ocean hypothesis. Previous studies have investigated the plausibility of an ancient ocean on Mars by examining the topography of ancient putative sea-level markers on the planet's surface. A previous study has argued that topographic benches, or contacts, are ancient shorelines, and that these contacts display long-wavelength topographic variations consistent with post-depositional true polar wander (Perron et al., Nature, 2007). In contrast, a second study has argued that the topography of ancient deltaic deposits associated with an ocean on early Mars are not consistent with the true polar wander scenario (Achille & Hynek, Nature Geosci., 2010). We revisit this issue by examining another marker of ancient shorelines --- the fluvial valley networks observed on the surface of Mars. Our results provide further evidence that a true polar wander event drove significant post-depositional deflection of surface features related to an ancient Martian ocean.