20-EPN-038: The strange behaviour of highly viscous mud in the low pressure environment: why the mixture changes its volume?
Visit by Petr Brož, Institute of Geophysics of the Czech Academy of Science (Czech Republic) to TA2.20 Open University Mars Chamber (UK).
Dates of visit: 6-17 December 2021
Report Summary: We performed multiple mud experiments inside a low-pressure chamber to investigate whether the volume of mud changes once exposed to the reduced atmospheric pressure of Mars. Our results show that mud extruded onto the surface under martian environmental conditions increases its volume and hence behaves differently than on Earth. The low atmospheric pressure causes instability of the water present in the mud mixture, leading to the formation of bubbles, which increase the volume of the mud.
These bubbles are then trapped within the mud. The buoyancy of the bubbles is not sufficient to overcome the drag force within the viscous material and rise to the surface. Hence, these bubbles remain trapped and gradually grow up to centimetre scale sizes. During their growth they push the mud out of the container resulting in horizontal and vertical inflation of the mud surface over cm-scales.
This behaviour is not observed at terrestrial mud flows, but it is somewhat similar to volumetric changes associated with degassing of some terrestrial lavas or mud volcano eruptions. Our experimental approach hence shows that viscous mud exposed to reduced atmospheric pressure behaves differently to on Earth.
Full scientific report published by kind permission of Petr Brož.
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