Periodic Bedrock Ridge Formation via Shielding and Interbedform Erosion: Wind Tunnel Experiments, a Field Analog, and Survey of Mars

Abstract Periodic bedrock ridges (PBRs) are enigmatic landforms carved by wind on Mars. Although they have been demonstrated to be erosional features carved into lithified bedrock, the precise cause of the ridge and groove topography is not fully understood. Previous work has suggested that aeolian bedforms may have been required to form the periodicity, but some questions about this mechanism still remain. Can interbedform erosion lead to ridge‐and‐trough topography? To test this, we conducted a wind tunnel experiment simulating the proposed landscape formation mechanism. Additionally, we studied a field analog system where bedforms armored a hardened mud substrate. Results from these supplement observations of known and new PBR fields on Mars. The preponderance of evidence suggests that the topography derives from interbedform erosion: Bedforms shield the substrate directly beneath them, but abrasion deflates the exposed material between bedforms. Eventually, abrasion in the deflating troughs undercuts the shielding bedforms, causing them to winnow and narrow. This leads to remnant bedforms perched on ridges that separate the deepening troughs and ultimately the characteristic periodic ridge topography. This mechanism requires that the shielding bedforms' migration rate is slow with respect to the local rate of aeolian erosion. Examples of modern bedforms near periodic ridges on Mars suggest that the erosional features respond to the largest wavelengths in overlying bedform fields, filtering out the signal of small bedforms. Overall, the combined evidence from wind tunnel experiments, field work, and remote sensing supports the formation of PBRs via aeolian deflation between aeolian bedforms.