Gas release from ice/dust mixtures: results from eleven KOSI experiments

Lämmerzahl, P.; Gebhard, J.; Grün, E.; Klees, G.

doi:10.1016/0032-0633(94)00121-7

Cited by 14 publications

(9 citation statements)

References 18 publications

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“…Therefore, the height of the samples decreases only slightly during these experiments. This process was already observed in earlier experiments (e.g., Grün et al 1993;Kührt & Keller 1994;Lämmerzahl et al 1995) and could be a source of dust that covers substantial parts of the surface of 67P (Thomas et al 2015a;Lai et al 2016). It must be noted that significant amounts of dust are redeposited on 67P and substantial dust blankets do not have to have formed in situ on the comet's surface (Kramer & Noack 2015;El-Maarry et al 2016;Lai et al 2017;Cambianica et al 2020).…”

Section: Vol% and 33 Vol% Water Ice Contentsupporting

confidence: 65%

“…The KOSI laboratory experiments in the 1990s simulated and studied sublimation processes that were expected on the surfaces of comets (e.g., Grün et al 1989Grün et al , 1993Lämmerzahl et al 1995). In a sublimation chamber, mixtures of water ice and nonvolatile analog materials were illuminated by an energy source and the changes in the samples' surfaces were analyzed.…”

Section: Introductionmentioning

confidence: 99%

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Sublimation of ice-dust mixtures in cooled vacuum environments to reproduce cometary morphologies

Haack

Lethuillier

Kreuzig

et al. 2021

A&A

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Aims. The morphology of cometary surfaces can provide important information to constrain the composition and evolution of comets. In this work, we investigate the sublimation behavior of comet analog materials and how the sample composition affects the evolution of morphological features in laboratory experiments. In our experiments, we used dust ice mixtures as analog material to form observed cometary morphologies. Methods. We used ice-dust mixtures in different mixing ratios as cometary analog material. In order to obtain realistic results, we scaled the expected cohesive and gravitational forces on comets to laboratory conditions. The samples were placed in a vacuum sublimation chamber and permanently cooled down to temperatures below 150 K to simulate the space environment. In the experiment, the samples were insolated with a light source from two different directions and alterations on the surface were recorded with a camera. Results. We find that the morphology of sublimation residues of ice-dust mixtures is strongly dependent on the ice-dust ratio as well as the insolation direction. High amounts of ice cause constant surface alteration and lead to exotic morphologies. Low amounts cause fewer and more episodic surface changes during its sublimation. Collapse events resulting in irregular and very rough surfaces occur during horizontal insolation.

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Section: Vol% and 33 Vol% Water Ice Contentsupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Sublimation of ice-dust mixtures in cooled vacuum environments to reproduce cometary morphologies

Haack

Lethuillier

Kreuzig

et al. 2021

A&A

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“…Ejection of water ice grains has been observed in the KOSI comet simulation experiments (Grün et al 1993;Lämmerzahl et al 1995). Broad absorption features of water ice at 1.5 and 2.05 µm were detected in near-infrared spectra of Hale-Bopp at 7 AU (Davies et al 1997).…”

Section: Icy Grainsmentioning

confidence: 87%

Broadband infrared photometry of comet Hale-Bopp with ISOPHOT

Grün

Hanner

Peschke

et al. 2001

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Abstract. Comet Hale-Bopp was observed five times with ISOPHOT, the photometer on board ESA's Infrared Space Observatory (ISO) between 4.6 and 2.8 AU. Each time, broadband photometry was performed using 4 different detectors, 5 apertures and 10 filters covering the range between 3.6 and 170 µm. Background observations were performed with identical instrument settings at the same positions on the sky several days after the comet observations. The observation strategy and the data reduction steps are described in some detail, including the techniques to correct for variable detector responsivity. The resulting inband power values of the Hale-Bopp observations and their uncertainties are given. The mean uncertainty is 25%. The final fluxes were computed, taking into account the zodiacal background, possible offset of the comet's position from the center of the aperture, the brightness distribution within the coma, and the spectral energy distribution of the comet's emission. Strong thermal emission from a broad size distribution of dust particles was detected in all of the data sets, even at r = 4.6-4.9 AU pre-perihelion and 3.9 AU post-perihelion; the total thermal energy varied as r −3 . The 7.3-12.8 µm color temperature was ∼1.5 times the blackbody temperature, higher than that observed in any other comet. Silicate features at 10 and 25 µm were prominent in all 5 data sets, the largest heliocentric distances that silicate emission has been detected in a comet. The presence of crystalline water ice grains is suggested from the 60 µm excess emission at 4.6-4.9 AU, consistent with the observed QOH if the icy grains were slightly warmer than an equilibrium blackbody. The average albedo of the dust is higher than that of comet P/Halley, but lower than other albedo measurements for Hale-Bopp nearer perihelion. There is no evidence for a component of cold, bright icy grains enhancing the scattered light at 4.6 AU. Simple models for a mixture of silicate and absorbing grains were fit to the ISO spectra and photometry at 2.8 AU. The observed flux at λ > 100 µm requires a size distribution in which most of the mass is concentrated in large particles. Dust production rates of order 1.5 × 10 5 kg s −1 at 2.8 AU and 3 × 10 4 kg s −1 at 4.6 AU have been found. They correspond to dust to gas mass ratios of 6 to 10. † Deceased.Article published by EDP Sciences and available at http://www.aanda.org or http://dx

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“…Through this process a comet loses material during each orbit until it finally extinguishes. In the 1990s sublimation experiments with dust-ice mixtures were performed as part of the KOSI (KOmetenSImulation) project to simulate and understand these cometary surface processes (e.g., Grün et al 1989Grün et al , 1993Lämmerzahl et al 1995). However, these experiments are not suitable and were not designed to understand complex morphologies such as cliffs, cracks, or mass movements that have only later been observed on 67P/Churyumov-Gerasimenko (Thomas et al 2015;Pajola et al 2016;El-Maarry et al 2019).…”

Section: Introductionmentioning

confidence: 99%

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

Haack

Otto

Gundlach

et al. 2020

A&A

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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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Gas release from ice/dust mixtures: results from eleven KOSI experiments

Cited by 14 publications

References 18 publications

Sublimation of ice-dust mixtures in cooled vacuum environments to reproduce cometary morphologies

Sublimation of ice-dust mixtures in cooled vacuum environments to reproduce cometary morphologies

Broadband infrared photometry of comet Hale-Bopp with ISOPHOT

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

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