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New observation of granular slide mass-wasting on Europa

Presentation #315.07 in the session Icy Satellites: Surfaces, Ice Shell, and Interior (Poster + Lightning Talk)

Published onOct 23, 2023
New observation of granular slide mass-wasting on Europa

Background: On Europa, mass wasting deposits show similar behaviors to those observed across the solar system, on bodies such as Vesta, Ceres, Iapetus, Moon, and Mars [1-6]. Based on the emplacement morphology, we categorize Europan mass-wasting features into slides (47 total), slumps (2 total), and flow-like features (5 total). Overall, slides are the most commonly observed mass-wasting feature, and the majority (n=31) of them are clustered within the Conamara region, likely due to the distribution of Galileo high-resolution data. Fig. 1a shows the example of a sliding feature where we observe the downward motion of the deposit, exposing bedrock chutes at the crest and partially buried rocks within the deposit region (red arrows in Fig. 1a, resolution: 9 m/pixel). Typically, these types of features are common in the case of granular flows where granular particles experience mobility and follow the slope until the angle of repose is achieved [7].

Heim’s ratio: In general, the mobility of mass wasting deposits is measured by estimating the friction coefficient ratio (µ) also known as Heim’s ratio [8]. Here, the drop height-to-runout length ratio, H/L, is commonly used as a proxy for friction coefficient. On Earth and Mars, there is a trend for decreasing H/L with increasing deposit L (Fig. 1b). Likewise, slides on Europa follow this trend but do not show a strong correlation (slope is -0.40±0.3). The values scatter between 0.1- 0.6, and for similar H/L a range of deposit L is observed. Overall, the friction between Europan particles is inferred to be somewhat similar to Earth and Mars, but their mobility is relatively restricted. The lack of dependence of H/L on L could be controlled by surface slope, regolith volume, and/or rheological mechanism [1-6].

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