Aeolian dune sediment flux heterogeneity in Meridiani Planum, Mars

Abstract

It is now known unambiguously that wind-driven bedform activity is occurring on the surface of Mars today, including early detections of active sand dunes in Meridiani Planum's Endeavour crater. Many of these reports are only based on a few sets of observations of relatively isolated bedforms and lack regional context. Here, we investigate aeolian activity across central Meridiani Planum and test the hypothesis that dune sites surrounding Endeavour crater are also active and part of region-wide sediment migration driven by northwesterly winds. All 13 dune fields investigated clearly showed evidence for activity and the majority exhibited dune migration (average rates of 0.6 m/Earth-year). Observations indicate substantial geographic and temporal heterogeneity of dune crest fluxes across the area and per site. Locations with multiple time steps indicate dune sand fluxes can vary by a factor of five, providing evidence for short periods of rapid migration followed by near-stagnation. In contrast, measurements at other sites are nearly identical, indicating that some dunes are in a steady-state as they migrate. The observed sediment transport direction was consistent with a regional northeasterly-to-northwesterly wind regime, revealing more variations than were appreciated from earlier, more localized studies. Craters containing shallow, degraded, flat-floored interiors tended to have dunes with high sediment fluxes/activity, whereas local kilometer-scale topographic obstructions (e.g., central peaks, yardangs) were found to be inversely correlated with dune mobility. Finally, the previous, more limited detections of dune activity in Endeavour crater have been shown to be representative of a broader, region-wide pattern of dune motion.

Climate Forcing of Ripple Migration and Crest Alignment in the Last 400 kyr in Meridiani Planum, Mars

“…org/multimedia/space-images/mars/opportunity-sol-3330-3331-navcam-360-dust-devil-1.html), but this observation does not provide much information about the strong, sustained winds required to construct, reorient, or reactivate bedforms. Observations from HiRISE images of large dark dune migration in nearby craters indicated net southeast-ward to southwest-ward transport (Chojnacki et al, 2017), which is contrary to the dominantly westward sand transport suggested by the MGCM results in Figure 4. Chojnacki et al (2015) showed that in Endeavour crater, winds from the northwest drove intracrater bedform migration over much of the Martian year (L s = 180-85°).…”

Numerical Study of Shear Stress Distribution Over Sand Ripples Under Terrestrial and Martian Conditions

“…Our results thus overestimate the shear stress during saltation. This effect is much more significant for Earth than for Mars where the sand flux is generally an order of magnitude smaller (see Table ; Chojnacki et al, ). In addition, the saltation flux on Mars will further reduce the simulated shear velocity over the ripples; thus, our results suggest that for ambient wind speeds up to at least 15 m/s, no direct entrainment would occur from the ripple crests.…”

Wind in Jezero Crater, Mars

“…Dunes are common on Mars (Hayward et al, 2007) and have been mapped in the vicinity of Jezero crater . Observed migration of dunes on Mars suggests lee faces can be reworked, and dune morphology can record a distinct wind direction on timescales of a few years to single decades (e.g., Banks et al, 2018;Bridges et al, 2013;Chojnacki et al, 2017). Observed migration of dunes on Mars suggests lee faces can be reworked, and dune morphology can record a distinct wind direction on timescales of a few years to single decades (e.g., Banks et al, 2018;Bridges et al, 2013;Chojnacki et al, 2017).…”