The Martian North Polar Layered Deposits (NPLD) are composed of
alternating water-ice and dust layers resulting from atmospheric
deposition and are key to understanding Mars’ climate cycles. Carved
within these deposits are spiral troughs, whose migration affects
deposition signals. To understand the relationship between NPLD
stratigraphy and Martian climate, we must first identify the modern-day
drivers of NPLD ice migration. The prevailing theory posits migration is
driven by upstream-migrating bed undulations bounded by hydraulic jumps,
caused by katabatic winds flowing over trough walls with asymmetric
relief in cross-section. This is supported by trough-parallel clouds,
whose formation can be first order attributed to hydraulic jumps.
We present an updated cloud atlas across the Martian north pole using
~13,800 Thermal Emission Imaging System images spanning
~18 earth years. We find evidence of trough-parallel
clouds in ~400 images, where regions nearer to the pole
have the highest cloud frequency. We also compare spiral trough geometry
(i.e., trough wall slopes and relief, width, depth) to our cloud atlas.
We find regions with trough-parallel clouds often correlate with metrics
suggested to be associated with modern-day erosion-deposition cycles
(i.e., wall relief and asymmetry), but not always, and in some regions,
troughs with morphologies conducive to cloud formation have no clouds.
Overall, we show trough geometry to vary greatly across the deposits,
both within and between troughs, suggestive of localized differences in
deposition relative to migration, varying katabatic wind intensities, or
the possibility of additional mechanisms for trough initiation and
migration (e.g., in-situ trough erosion).