Aerodynamics of Mars 2020 Rover Wind Sensors

Bardera, Rafael; Sor, Suthyvann; García-Magariño, Adelaida

doi:10.5772/intechopen.90912

Cited by 4 publications

(2 citation statements)

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“…The relative importance of these forces plays a big role in both erosional (de Haas & Woerkom, 2016; Roelofs et al., 2022) and depositional processes (de Haas, Braat, et al., 2015; Zhou et al., 2019) and is, therefore, an important tool in understanding how certain flows lead to certain morphological features. The Bagnold number describes the ratio between collisional and viscous forces (Iverson, 1997):

Nb=\frac{{v}_{s}{\rho }_{s}{\delta }^{2}\gamma }{{v}_{f}\mu }

wherein v s is the volumetric solids fraction, ρ s is the density of the sediment grains, δ is the D 50 (median) grain size of the sediment (m), v f is the volumetric fluid fraction, μ is the dynamic viscosity of CO 2 gas under Martian atmospheric conditions, which is 9.82 × 10 −6 Ns/m 2 (Bardera et al., 2020), and γ is the flow shear rate (1/ s ):

\gamma =\frac{u}{H}

wherein u is the is the flow velocity (m/s). According to Iverson (1997), collisional forces dominate at N b > 200.…”

Section: Methodsmentioning

confidence: 99%

“…wherein v s is the volumetric solids fraction, ρ s is the density of the sediment grains, δ is the D 50 (median) grain size of the sediment (m), v f is the volumetric fluid fraction, μ is the dynamic viscosity of CO 2 gas under Martian atmospheric conditions, which is 9.82 × 10 6 Ns/m 2 (Bardera et al, 2020), and γ is the flow shear rate (1/s):…”

Section: Flow Characterizationmentioning

confidence: 99%

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The Dynamics of CO₂‐Driven Granular Flows in Gullies on Mars

Roelofs,

Conway,

van Dam

et al. 2024

JGR Planets

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Martian gullies are landforms consisting of an erosional alcove, a channel, and a depositional apron. A significant proportion of Martian gullies at the mid‐latitudes is active today. The seasonal sublimation of CO2 ice has been suggested as a driver behind present‐day gully activity. However, due to a lack of in situ observations, the actual processes causing the observed changes remain unresolved. Here, we present results from flume experiments in environmental chambers in which we created CO2‐driven granular flows under Martian atmospheric conditions. Our experiments show that under Martian atmospheric pressure, large amounts of granular material can be fluidized by the sublimation of small quantities of CO2 ice in the granular mixture (only 0.5% of the volume fraction of the flow) under slope angles as low as 10°. Dimensionless scaling of the CO2‐driven granular flows shows that they are dynamically similar to terrestrial two‐phase granular flows, that is, debris flows and pyroclastic flows. The similarity in flow dynamics explains the similarity in deposit morphology with levees and lobes, supporting the hypothesis that CO2‐driven granular flows on Mars are not merely modifying older landforms, but they are actively forming them. This has far‐reaching implications for the processes thought to have formed these gullies over time. For other planetary bodies in our solar system, our experimental results suggest that the existence of gully like landforms is not necessarily evidence for flowing liquids but that they could also be formed or modified by sublimation‐driven flow processes.

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