Megaripples are distinct wind-driven bedforms that occur on the surface of Earth and Mars. Caused by the action of wind, they are of the sizes between that of smaller ripples and larger dunes.
Scientists recently identified abundant megaripple populations across the north polar region of Mars. These megaripples were found to be migrating with dunes and ripples.
Planetary Science Institute Research Scientist Matthew Chojnacki said, “Using repeat HiRISE images acquired over long durations – six Mars years or 13 Earth years – we examined the dynamic activity of polar bedforms. We found the thin Martian atmosphere can mobilize some coarse-grained megaripples, overturning prior notions that these were static relic landforms from a past climate. We mapped megaripples and adjacent bedforms across the north polar sand seas, the most expansive collection of dune fields on Mars.”
“Part of the uncertainty when studying planetary polar landforms is the long, cold polar winter that eventually covers the region in carbon dioxide and water ice. For wind-driven bedforms, such as megaripples, that means they are unable to migrate for nearly half of the year. However, it appears the late spring and summer winds that descend off the polar cap more than makeup for these other periods of inactivity.”
“Megaripples were found to be widespread across the region and migrating at relatively high rates relative to other sites on Mars that are at lower latitudes. This enhanced activity is likely related to the greater sand fluxes found for neighboring dunes driven by summer-time seasonal winds when polar ice is sublimating. This supports the idea that much of the Martian surface is modified and not just ancient or static. In contrast, other megaripples appear to be stabilized, a likely result of inter-granular ice within low wind areas.”
Journal Reference:
- Matthew Chojnacki et al. Widespread Megaripple Activity Across the North Polar Ergs of Mars. DOI: 10.1029/2021JE006970