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How strong is a cometary dust layer?

Presentation #408.01 in the session Comets: Nucleus (Oral Presentation)

Published onOct 23, 2023
How strong is a cometary dust layer?

The activity of comets is a well known phenomenon and clearly visible from earth. The cometary tail consists out of dust particles, which are lifted from the nucleus by the gas flow created by sublimation. In order to understand the physics of dust ejection it is important to know how strong the dust is bonded to the surface. To lift of the dust the tensile strength must be overcome, hence measuring it is important. In the CoPhyLab we designed an experimental setup which allows measurements of the tensile strength in vacuum by performing the Brazilian Disk Test on samples, which had water ice in them and were fully outgassed. This unique setup allows the direct measurement of dust crusts, which can only be created by letting ice dust mixtures outgas. The results from this work show tensile strength of 50Pa for an outgassed dust crust with a volume filling factor 15%, which is fifty times lower than previous measurements performed on samples with the same volume filling factor but without the inner structure created by the outgassing. Also, a strong influence of the vacuum was seen in these experiments, making some samples up to ten times stronger, which is caused by removing water vapour from the dust surface.

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