Sintering and sublimation of micrometre-sized water-ice particles: the formation of surface crusts on icy Solar System bodies

Gundlach, Bastian; Ratte, Judy; Blum, Jürgen; Oesert, Joachim; Gorb, Stanislav N.

doi:10.1093/mnras/sty1839

Cited by 29 publications

(29 citation statements)

References 25 publications

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“…The growth of the sinter neck can significantly increase the strength of the material as shown by Fig. 9 (derived from the sinter model provided by Gundlach et al 2018b). However, it is important to note that the sintering is only a short-term effect because sublimation will always lead to evaporation of the contact area.…”

Section: Strength From Laboratory Experimentsmentioning

confidence: 99%

“…The first panel shows a typical temperature distribution (T) inside the surface layers of the cometary nucleus derived from a thermophysical model developed by Blum et al (2017). In the second panel, the evolved sinter neck (rn) between the ice particles is shown (based on the sinter model described in Gundlach et al 2018b). The next three panels are visualizing the change of the tensile strength (σ), the change of the turnover point of the compression curve (pm) and the change of the thermal conductivity (l).…”

Section: Strength From Laboratory Experimentsmentioning

confidence: 99%

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The Thermal, Mechanical, Structural, and Dielectric Properties of Cometary Nuclei After Rosetta

et al. 2019

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The physical properties of cometary nuclei observed today relate to their complex history and help to constrain their formation and evolution. In this article, we review some of the main physical properties of cometary nuclei and focus in particular on the thermal, mechanical, structural and dielectric properties, emphasizing the progress made during the Rosetta mission. Comets have a low density of 480 ± 220 kg m -3 and a low permittivity of 1.9 -2.0, consistent with a high porosity of 70 -80 %, are weak with a very low global tensile strength <100 Pa, and have a low bulk thermal inertia of 0 -60 J K -1 m -2 s -1/2 that allowed them to preserve highly volatiles species (e.g. CO, CO2, CH4, N2) into their interior since their formation. As revealed by 67P/Churyumov-Gerasimenko, the above physical properties vary across the nucleus, spatially at its surface but also with depth. The broad picture is that the bulk of the nucleus consists of a weakly bonded, rather homogeneous material that preserved primordial properties under a thin shell of processed material, and possibly covered by a granular material; this cover might in places reach a thickness of several meters. The properties of the top layer (the first meter) are not representative of that of the bulk nucleus. More globally, strong nucleus heterogeneities at a scale of a few meters are ruled out on 67P's small lobe.

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Section: Strength From Laboratory Experimentsmentioning

confidence: 99%

Section: Strength From Laboratory Experimentsmentioning

confidence: 99%

The Thermal, Mechanical, Structural, and Dielectric Properties of Cometary Nuclei After Rosetta

et al. 2019

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“…The possible dissimilarity of grain size between Saturn's and Jupiter's moons may be due to their different surface temperatures, ranging from 80 to 130 K for Europa but from 50 to 100 K for Enceladus and Rhea (Howett et al, 2010;Spencer et al, 1999). As shown by Clark et al (1983) and Gundlach et al (2018), temperatures above 100 K allow the mobility of the ice, resulting in grain growth and sintering, impeded at lower temperatures. Moreover, the resurfacing mechanisms of these satellites may be significantly different.…”

Section: 1029/2018je005753mentioning

confidence: 99%

Polarimetry of Water Ice Particles Providing Insights on Grain Size and Degree of Sintering on Icy Planetary Surfaces

et al. 2018

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The polarimetry of the light scattered by planetary surfaces is a powerful tool to provide constraints on their microstructure. To improve the interpretation of polarimetric data from icy surfaces, we have developed the POLarimeter for ICE Samples complementing the measurement facilities of the Ice Laboratory at the University of Bern. The new setup uses a high precision Stokes polarimeter to measure the degree of polarization in the visible light scattered by surfaces at moderate phase angles (from 1.5° to 30°). We present the photometric and polarimetric phase curves measured on various surfaces made of pure water ice particles having well‐controlled size and shape (spherical, crushed, and frost). The results show how the amplitude and the shape of the negative polarization branch change with the particles sizes and the degree of metamorphism of the ice. We found that fresh frost formed by water condensation on cold surfaces has a phase curve characterized by resonances (Mie oscillations) indicating that frost embryos are transparent micrometer‐sized particles with a narrow size distribution and spherical shape. Comparisons of these measurements with polarimetric observations of the icy satellites of the Solar System suggest that Europa is possibly covered by relatively coarser (~40–400 μm) and more sintered grains than Enceladus and Rhea, more likely covered by frost‐like particles of few micrometers in average. The great sensitivity of polarization to grain size and degree of sintering makes it an ideal tool to detect hints of ongoing processes on icy planetary surfaces, such as cryovolcanism.

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“…The pressure exerted in the moment of the breakup refers to the tensile strength and can be analyzed. So far, using the Brazilian disk test method, the tensile strength has only been measured for the pure components from which a comet could be formed, for example, water ice, or dust with a tensile strength of a few kilopascals (Gundlach et al 2018a;Steinpilz et al 2019) or granular organic materials (Bischoff et al 2020). In this study, we present Brazilian disk test measurements of mixtures of different components that could be considered as cometary analog materials and show their dependence on particle shape, tensile strength, filling fraction, and surface energy.…”

Section: Introductionmentioning

confidence: 99%

Tensile strength of dust-ice mixtures and their relevance as cometary analog material

Haack

Otto

Gundlach

et al. 2020

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Aims. The tensile strength of granular matter is of great importance to our understanding of the evolution of comets and to our attempts to reproduce processes on cometary surfaces in laboratory experiments. In this work, we investigate the tensile strength of three different materials and their mixtures, which can be used as cometary analog materials in the laboratory. Methods. We used two types of siliceous dusts and granular water ice whose polydisperse particles were either angular or spherical. Our samples were cooled to below 150 K to better simulate the conditions of a cometary surface and to avoid thermal alteration of the material. We used the Brazilian disk test method to exert stress on the cooled samples and determine the tensile strength at the moment the samples broke. Results. We find that the tensile strength of two component mixtures is strongly dominated by the component with the higher tensile strength. The materials made of mostly angular dust particles have a lower filling fraction, but a higher tensile strength compared to materials made of spherical particles. Furthermore, the tensile strength of the cooled components is substantially lower than the tensile strength of the same components at room temperature. This implies that the surface energy of the investigated materials at low temperatures is significantly lower than previously assumed.

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Sintering and sublimation of micrometre-sized water-ice particles: the formation of surface crusts on icy Solar System bodies

Cited by 29 publications

References 25 publications

The Thermal, Mechanical, Structural, and Dielectric Properties of Cometary Nuclei After Rosetta

The Thermal, Mechanical, Structural, and Dielectric Properties of Cometary Nuclei After Rosetta

Polarimetry of Water Ice Particles Providing Insights on Grain Size and Degree of Sintering on Icy Planetary Surfaces

Tensile strength of dust-ice mixtures and their relevance as cometary analog material

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