Formation of gravel-mantled megaripples on Earth and Mars: Insights from the Argentinean Puna and wind tunnel experiments

Bridges, N. T.; Spagnuolo, M. G.; Silva, De; Zimbelman, J. R.; Neely, E. M.

doi:10.1016/j.aeolia.2015.01.007

Cited by 35 publications

(28 citation statements)

References 33 publications

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“…Coarse-grained ripples on Earth typically form in grains larger than about a millimeter up to several centimeters (e.g., 12,21,58,59). Such coarsegrained ripples were observed on Mars by the Spirit rover at "El Dorado" in Gusev crater (60), and by the Curiosity rover at the base of the stoss slope of "High Dune" in Gale crater, as expected at the upwind margin of a dune field (61).…”

Section: S15 Additional Evidence In Favor Of the Wind-drag Hypothesismentioning

confidence: 82%

Large wind ripples on Mars: A record of atmospheric evolution

Lapôtre

Ewing

Lamb

et al. 2016

Science

161

357

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Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter– to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typically have asymmetric profiles with angle-of-repose lee slopes and sinuous crest lines, making them unlike terrestrial wind ripples. Rather, these structures resemble fluid-drag ripples, which on Earth include water-worked current ripples, but on Mars instead form by wind because of the higher kinematic viscosity of the low-density atmosphere. A reevaluation of the wind-deposited strata in the Burns formation (about 3.7 billion years old or younger) identifies potential wind-drag ripple stratification formed under a thin atmosphere.

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Section: S15 Additional Evidence In Favor Of the Wind-drag Hypothesismentioning

confidence: 82%

Large wind ripples on Mars: A record of atmospheric evolution

Lapôtre

Ewing

Lamb

et al. 2016

Science

161

357

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“…Similarly, in terrestrial wind tunnels it has been shown that clasts undergo distinct stages of threshold, starting with vibrating, then transitioning to intermediate sliding and rolling (depending on the substrate), and concluding with detachment. In these studies, the vibration threshold was measured at about 50–60% of that at saltation [ Bridges et al , ]. It is very likely that the particle movement observed in this low wind period which overlapped with the Bagnold Dune Campaign was from such intermediate stage processes.…”

Section: Discussionmentioning

confidence: 99%

Martian aeolian activity at the Bagnold Dunes, Gale Crater: The view from the surface and orbit

et al. 2017

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The first in situ investigation of an active dune field on another planetary surface occurred in 2015–2016 when the Mars Science Laboratory Curiosity rover investigated the Bagnold Dunes on Mars. High Resolution Imaging Science Experiment images show clear seasonal variations that are in good agreement with atmospheric model predictions of intra‐annual sand flux and migration directions that together indicate that the campaign occurred during a period of low wind activity. Curiosity surface images show that limited changes nevertheless occurred, with movement of large grains, particularly on freshly exposed surfaces, two occurrences of secondary grain flow on the slip face of Namib Dune, and a slump on a freshly exposed surface of a large ripple. These changes are seen at Martian solar day (sol)‐to‐sol time scales. Grains on a rippled sand deposit and unconsolidated dump piles show limited movement of large grains over a few hours during which mean friction speeds are estimated at 0.3–0.4 m s−1. Overall, the correlation between changes and peak Rover Environmental Monitoring Station (REMS) winds is moderate, with high wind events associated with changes in some cases, but not in others, suggesting that other factors are also at work. The distribution of REMS 1 Hz wind speeds shows a significant tail up to the current 20 m s−1 calibration limit, indicating that even higher speed winds occur. Nonaeolian triggering mechanisms are also possible. The low activity period at the dunes documented by Curiosity provides clues to processes that dominated in the Martian past under conditions of lower obliquity.

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“…In general, typical u ⁄ values range from 0.2 m/s (for well sorted fine sand both in wind tunnels and in a field setting) to 0.4 m/s (field measurements in diverse desert settings) at the threshold of sand motion (Bagnold, 1941;Greeley and Iversen, 1985;Nickling, 1988;Lancaster and Baas, 1998;Creyssels et al, 2009;Kok et al, 2012). The elevation of the Puna means that the atmospheric pressure and density is considerably lower than at sea level, which translates to the shear velocity at the Puna being about 1.7Â the value at sea level; hence, threshold shear velocity at the Puna study sites should be more like 0.4-0.7 m/s (de Silva et al, 2013;Bridges et al, 2015).…”

Section: Methodsmentioning

confidence: 98%

“…The megaripple gravels consist of a bimodal association of dense (>2 g cm À3 ) low-albedo volcanic and metamorphic clasts up to 2.5 cm in diameter, along with high-albedo pumice clasts (<1.5 g cm À3 ) up to 5 cm in diameter, typically concentrated in a surface layer <30 cm in thickness, all overlying a fine-grained interior displaying local layering that is conformable to the underlying bedrock surface (de Silva et al, 2013). The Puna gravel-mantled megaripples were investigated in order to evaluate these features as analogs for Transverse Aeolian Ridges on Mars (de Silva et al, 2013;Bridges et al, 2015). One aspect of the overall project was to determine the aerodynamic roughness height (z 0 ) associated with these large aeolian bedforms, a parameter that is critical to understanding the work that can be done by the wind on a particulate surface exposed to an atmosphere.…”

Section: Introductionmentioning

confidence: 99%