Computational Sedimentation Modelling Calibration: a tool to measure the settling velocity at different gravity conditions
Abstract. Research in zero or reduced gravity is essential to prepare and support planetary sciences and space exploration. In this study, an instrument specifically designed to measure the settling velocity of sediment particles under normal, hyper-, and reduced gravity conditions is presented. Once operational, it will be used to examine the quality of analogue terrestrial sedimentation environments for planetary research, especially for Mars. The lower gravity on Mars potentially reduces drag on particles settling in water, which in turn may affect the texture of sedimentary rocks forming in a given body of water moving down-slope. To assess the potential impact, an instrument was designed to simulate sediment settling at gravities different from Earth during parabolic flights. The trajectories of particles settling in water were recorded during the ascending part of a parabola (about 1.8 g), under reduced gravity conditions (Martian and lunar) and on Earth. The data were used to compute the terminal settling velocity of isolated and small groups of particles and compared to the results calculated using a semi theoretical formula derived in 2004 by Ferguson and Church (Ferguson & Church, 2004). The experimental data confirm the expected trend, i.e., that the values predicted using models calibrated with data collected at terrestrial gravity underestimate settling velocity on Mars. The results also demonstrate that the instrument is operational, providing a Martian gravity analogue for sedimentation studies on Earth.
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