Large-Scale HiRISE Survey Demonstrates a Genetic Relationship Between Martian Periodic Bedrock Ridges and Transverse Aeolian Ridges

Abstract:

Periodic Bedrock Ridges (PBRs) are erosional features found on the modern wind-dominated surface of Mars that form transverse with respect to dominant wind direction. PBRs are often observed to cross-cut strata and their formation is not well understood. They share morphologic similarities with Transverse Aeolian Ridges (TARs), an unconsolidated sedimentary bedform that is ubiquitous across the Martian surface, including shape, wavelength, and orientation with respect to wind. Both PBRs and TARs are found in close proximity and in similar geologic settings, even overlapping where sparse TAR bedforms trace the upper ridges of PBRs. These observations motivate the hypothesis that TARs and PBRs on Mars may share a genetic relationship, a model presented by Hugenholtz et al. (2015) based on observations of analogous features in Argentina.

To investigate this potential relationship, we survey the Martian surface for sites where TARs and PBRs occur in close proximity using three strategies. First, we examine HiRISE images around previously identified PBRs. Second, we survey all stereo HiRISE pairs with corresponding CRISM coverage located between +10 and -10 degrees latitude. Finally, we carry out a more focused survey in Ius Chasma, using HiRISE and CRISM data to characterize multiple occurrences of TAR-mantled PBRs. These surveys reveal TAR-mantled PBR sites on >40 HiRISE images, with the majority concentrated in Valles Marineris. In many cases, the spatial extent of PBR and TAR bedforms is identical, which could be consistent with a genetic relationship. Continued characterization of the morphology and setting of co-occurring TARs and PBRs will seek to constrain the direction of causality between them.