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Widespread megaripple activity found in Martian north pole region

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the surface of Earth and Mars. Here, Megaripples are shown at bottom center next to the North Pole sand dunes in this perspective view using data returned from the High-Resolution Imaging Science Experiment (HiRISE). These northern polar megariples and dunes produce the highest known sand fluxes on the planet, driven by summer katabatic winds modulated by the seasonal retreat of the CO2. The view is about 1 kilometer wide. Credit: HiRISE digital terrain model DTEPC_036176_2640_035926_2640_A01 and color orthoimage ESP_053345_2640. HiRISE data: NASA/JPL/University of Arizona” width=”600″ height=”270″/>

“Megalipples” are distinct wind-driven bedforms that occur on the surface of Earth and Mars. Here, Megaripples are shown at bottom center next to the North Pole sand dunes in this perspective view using data returned from the High-Resolution Imaging Science Experiment (HiRISE). These northern polar megariples and dunes produce the highest known sand fluxes on the planet, driven by summer katabatic winds modulated by seasonal CO2 stopper retreat. The view is about 1 kilometer wide. Credit: HiRISE digital terrain model DTEPC_036176_2640_035926_2640_A01 and color orthoimage ESP_053345_2640. HiRISE data: NASA/JPL/University of Arizona

Megaripples, mid-scale bedforms caused by wind action, have been widely studied and considered largely inactive relics of past climates, with few exceptions. A new paper by Planetary Science Institute researcher Matthew Chojnacki shows that abundant populations of megaripples have been identified in the north polar region of Mars and have been shown to migrate with dunes and ripples.

Mega-ripples on Mars are about 1-2 meters high and 5-40 meters apart, where their size ranges from ripples about 40 centimeters high with 1-5 meter spacing and dunes that can reach hundreds of meters in height with a spacing of 100 to 300 meters. While megaripple migration rates are slow by comparison (average of 0.13 meters per Earth year), some of the nearby ripples have been found to migrate an average equivalent of 9.6 meters per year in just 22 days in summer du North, unprecedented rates for March. These high rates of sand movement help explain megaripple activity.

“Using repeated HiRISE images acquired over long durations – six Martian years or 13 Earth years – we examined the dynamic activity of polar bedforms. We found that the thin Martian atmosphere can mobilize mega-jaws to large grains, overturning earlier notions that they were static relic landforms of a past climate.We mapped megaripples and adjacent bedforms across the North Pole sand seas, the most extensive collection vast array of dune fields on Mars,” said Chojnacki, lead author of “Widespread Megaripple Activity Across the North Polar Ergs of Mars” which appears in Journal of Geophysical Research: Planets.

Widespread megaripple activity in the Martian North Pole region

Polar bedform sites with active megaripples, as seen in HiRISE. The approximate direction of transport is down left and the inset is 100 yards wide. Credit: HiRISE data: NASA/JPL/University of Arizona

Part of the uncertainty when studying planetary polar landforms is the long, cold polar winter that eventually blankets the region in carbon dioxide and water ice. For wind-driven bedforms, such as Megariples, this means that they are unable to migrate for nearly half the year. “However, it appears that the late spring and summer winds coming down from the polar cap more than compensate for these other periods of inactivity,” Chojnacki said.






Megariples were found to be widespread throughout the region and migrating at relatively high rates compared to other sites on Mars that are at lower latitudes. This increased activity is likely related to the larger sand fluxes found for nearby dunes that are driven by DST seasonal winds when polar ice sublimates. This supports the idea that much of the Martian surface is actively modified and not just ancient or static.” said Chojnacki. “In contrast, other megariples appear to be stabilized, a likely result of intergranular ice in low wind areas.”


Order hidden in the windswept sand


More information:
Matthew Chojnacki et al, Widespread megaripple activity across Mars’ north polar ergs, Journal of Geophysical Research: Planets (2021). DOI: 10.1029/2021JE006970

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Quote: Widespread Megaripple Activity Found in Martian North Pole Area (January 12, 2022) Retrieved January 12, 2022 from https://phys.org/news/2022-01-widespread-megaripple-martian-north-pole.html

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