New Evidence of an Ancient Martian Ocean From the Global Distribution of Valley Networks

Abstract

We examine the connection between true polar wander (TPW) and the evidence for an ancient ocean on Mars. Previous studies have investigated the plausibility of a Mars ocean by examining the topography of possible ancient sea level markers on the planet's surface. One such study argued that features interpreted as ancient shorelines display long-wavelength topographic variations consistent with postformational TPW (Perron et al., 2007, https://doi.org/10.1038/nature05873). In contrast, a second study argued that the elevations of possible ancient deltaic deposits associated with an ocean on early Mars are not consistent with the TPW scenario (di Achille & Hynek, 2010, https://doi.org/10.1038/ngeo891). Herein we revisit this issue by examining another marker of ancient shorelines—fluvial valley networks observed on the surface of Mars. Our results support the existence of an ancient Martian ocean and that long-wavelength deformation of related surface features (ancient shorelines and valley networks) was driven by some combination of TPW and surface loading associated with the formation of the Tharsis volcanic province.