Morphology of transverse aeolian ridges (TARs) on Mars from a large sample: Further evidence of a megaripple origin?

Abstract

Using HiRISE digital terrain models (DTMs), we developed a large morphological dataset to examine the three-dimensional shape, size, and scaling of Martian transverse aeolian ridges (TARs). Considerable debate exists on the characteristic morphology of TARs and the origins of these enigmatic bedforms. Some researchers suggest polygenesis or multiple classes of similar bedforms. Reliably characterizing the morphology of TARs is an essential prerequisite to developing and evaluating process-based models of TAR genesis and unraveling aeolian processes on the surface of Mars. We present measurements of TAR morphology from a large, DTM-derived dataset (n = 2295). We focused on TARs with ‘simple’ morphologies in order enable more defensible discretization. Histograms and cumulative log-frequency plots of morphometric parameters (length, width, height, elongation ratio, and wavelength) indicate the sample represents a continuum of bedforms from a single population. A typical TAR from our dataset is 88.5m long (longest planview axis), 17.3m wide (shortest planview axis), 1.3m tall, and has a wavelength of 25.8m. Combined with these data, the bulk of evidence presented to date suggests that interpreting TARs as megaripples is the most viable working hypothesis.