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  • 1
    Publication Date: 2017-11-29
    Description: To understand the potential applicability of the process of ‘slush flow’ (a sediment-carrying flow with water and ice) to gullies on Mars, we undertook a series of flume experiments at Earth surface temperatures and pressures, which we subsequently scaled for Mars. Experiments were conducted in a 3 x 0.5 m hinged flume filled with medium-grain-size sand. The experiments were performed over a slope angle range of 10°–30°, corresponding to the slope range for gullies observed on Mars. A water ice mix, or ‘slush’, was flowed through a 19 mm-diameter silicone hose and released onto the surface at the top of the slope. A variety of morphometric parameters were measured on each form produced in the flume. The forms produced in our experiments developed the three principal morphological components of Martian gullies: alcove, channel and apron, and had a diversity of planimetric forms. The forms produced during simulations compared well to slush flows in terrestrial arctic climates, and open up the possibility that some Martian gullies may result from slush flows associated with the thawing of permafrost-active layers or surface frost under favourable thermal regimes. Supplementary material: A complete spreadsheet of all measurements summarized in Figures 5 and 6 is available at https://doi.org/10.6084/m9.figshare.c.3930613
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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  • 2
    Publication Date: 2018-02-28
    Description: Martian gullies were initially hypothesized to be carved by liquid water, due to their resemblance to gullies on Earth. Recent observations have highlighted significant sediment transport events occurring in Martian gullies at times and places where CO 2 ice should be actively sublimating. Here we explore the role of CO 2 sublimation in mobilizing sediment through laboratory simulation. In our previous experimental work, we reported the first observations of sediment slope movement triggered by the sublimation of CO 2 frost. We used a Mars regolith simulant near the angle of repose. The current study extends our previous work by including two additional substrates, fine and coarse sand, and by testing slope angles down to 10°. We find that the Mars regolith simulant is active down to 17°, the fine sand is active only near the angle of repose and the coarse sand shows negligible movement. Using an analytical model, we show that under Martian gravity motion should be possible at even lower slope angles. We conclude that these mass-wasting processes could be involved in shaping Martian gullies at the present day and intriguingly the newly reported CO 2 -creep process could provide an alternative explanation for putative solifluction lobes on Mars. Supplementary material: Video clips depicting sediment transport types are available at https://doi.org/10.6084/m9.figshare.5208847
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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