Sublimation coefficient of water ice under simulated cometary-like conditions

Kossacki, Konrad J.; Markiewicz, W. J.; Skorov, Yu. V.; Kömle, Norbert I.

doi:10.1016/s0032-0633(99)00037-9

Cited by 56 publications

(33 citation statements)

References 13 publications

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“…Gundlach et al (2011) updated this empirical relation using the results of experiments conducted with mixtures of water ice and a dust component consisting of silica spheres. These results agree well with those reported by Kossacki et al (1999) for temperatures below 195 K and above 230 K, but show some discrepancies in between, in particular, with a faster decrease of the sublimation coefficient as temperature increases.…”

Section: Insights From Laboratory Experimentssupporting

confidence: 92%

“…The so-called sublimation coefficient of water ice describes the difference between measurements and theory and can be used as a correction coefficient, for example, to correctly model the temperature at the surface of a sublimating comet nucleus. Kossacki et al (1999) proposed an empirical temperature dependence of the sublimation coefficient of pure water ice over the temperature range of 170-270 K, based on three different experimental datasets. The sublimation coefficient is close to 1 for temperatures lower than 195 K, decreases as the temperature increases from 195 K to 230 K, and then remains at a constant value of about 0.15 for higher temperatures.…”

Section: Insights From Laboratory Experimentsmentioning

confidence: 99%

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OSIRIS observations of meter-sized exposures of H₂O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments

Pommerol

Thomas

El‐Maarry

et al. 2015

A&A

109

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Since OSIRIS started acquiring high-resolution observations of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, over one hundred meter-sized bright spots have been identified in numerous types of geomorphologic regions, but mostly located in areas receiving low insolation. The bright spots are either clustered, in debris fields close to decameter-high cliffs, or isolated without structural relation to the surrounding terrain. They can be up to ten times brighter than the average surface of the comet at visible wavelengths and display a significantly bluer spectrum. They do not exhibit significant changes over a period of a few weeks. All these observations are consistent with exposure of water ice at the surface of boulders produced by dislocation of the weakly consolidated layers that cover large areas of the nucleus. Laboratory experiments show that under simulated comet surface conditions, analog samples acquire a vertical stratification with an uppermost porous mantle of refractory dust overlaying a layer of hard ice formed by recondensation or sintering under the insulating dust mantle. The evolution of the visible spectrophotometric properties of samples during sublimation is consistent with the contrasts of brightness and color seen at the surface of the nucleus. Clustered bright spots are formed by the collapse of overhangs that is triggered by mass wasting of deeper layers. Isolated spots might be the result of the emission of boulders at low velocity that are redepositioned in other regions.

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Section: Insights From Laboratory Experimentssupporting

confidence: 92%

Section: Insights From Laboratory Experimentsmentioning

confidence: 99%

OSIRIS observations of meter-sized exposures of H₂O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments

Pommerol

Thomas

El‐Maarry

et al. 2015

A&A

109

View full text Add to dashboard Cite

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“…The high value of the extrapolated surface temperature is an additional argument for this assumption. As shown by Kossacki et al (1999) a decrease of the effective sublimation coefficient leads to a visible growth of temperature (for a fixed insolation flux) and at the same time to a very small increase of the gas flux.…”

Section: 23mentioning

confidence: 82%

“…We have addressed this question in a recent paper (Kossacki et al 1999). In the current paper, however, we keep the classical assumption α s = α c = 1, in order to avoid confusion of too many different effects.…”

Section: Basic Equationsmentioning

confidence: 99%

A Model of Heat and Mass Transfer in a Porous Cometary Nucleus Based on a Kinetic Treatment of Mass Flow

Skorov

2001

Icarus

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“…The values of the parameters applied here are the same as in the papers by Davidsson and Skorov (2002b) and Skorov et al (2002). Note that the porous character of the medium is taken into account phenomenologically by introducing into the heat-conductivity formula the so-called Hertz factor h , which characterizes the contact area between particles in a porous medium and takes values from 1 to 0.001 in different calculations (Kossacki et al , 1999):…”

Section: The Model Of Heat and Mass Transfermentioning

confidence: 99%

Direct statistical simulation of the near-surface layers of the cometary atmosphere. I. A spherical nucleus

2004

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The key to the explanation of the variety of processes associated with the activity of comets lies in a more profound understanding of the events that occur in the near-surface layer of the cometary nucleus and in the inner part of the cometary atmosphere, which is formed under the action of solar radiation. A complete description of the mass-and energy-transfer processes inside and outside the cometary nucleus, which can be presented as a body with a complex morphology and high porosity and which is composed of mineral, organic, and volatile components, is an extremely complicated problem of space physics. The nucleus and the inner part of the coma are closely related to each other as physical subsystems, and physical processes in these regions are in close symbiosis because of the permanent exchange of both energy and mass. The thermophysical model of the circumnuclear coma cannot be confined only to the consideration of the processes in the nucleus-the entire system should be simulated as a whole. A consistent model of the inner part of a cometary atmosphere of this kind has been developed in this paper within the framework of the gas-kinetic approach. Based on direct statistical simulation with weights, we simulated the two-dimensional gas flow from the cometary nucleus. The nucleus was assumed to be spherical. We considered different models of the nucleus morphology that determined the effective gas production: the homogeneous nucleus, the "spotty" nucleus with its active area in the vicinity of the subsolar point, and the "spotty" nucleus with its active area in the form of a spherical segment. For the first time, the boundary conditions at the inner boundary of the simulation domain required for the kinetic modeling of the inner coma were found from a self-consistent model of the heat and mass transfer in a porous cometary nucleus. The model was earlier developed by the authors. The basic new features of the model included taking into account the volumetric character of the radiation absorption in a porous medium, the kinetic simulation of the transport of sublimation products in the pores, and the consideration of the backward fluxes from the coma due to the intermolecular collisions. The kinetic simulation was performed using the SMILE program package. The parallel computer implementation of the model made it possible to calculate the spatial fields of the basic macrocharacteristics of the gas flow. It was demonstrated that the structure of the inner coma is essentially dependent on variations in the effective gas production. In all the cases considered, the main part of the coma is far from thermodynamic equilibrium. This means that the entire structure of the inner cometary atmosphere can be accurately studied only within the framework of the kinetic approach. In a general case, it can result from the interaction of gas flows generated by different active subregions on the nucleus surface. Thus, fine structures are formed and local efficient gas recondensation from the coma occurs in the model for some...

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Sublimation coefficient of water ice under simulated cometary-like conditions

Cited by 56 publications

References 13 publications

OSIRIS observations of meter-sized exposures of H₂O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments

OSIRIS observations of meter-sized exposures of H₂O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments

A Model of Heat and Mass Transfer in a Porous Cometary Nucleus Based on a Kinetic Treatment of Mass Flow

Direct statistical simulation of the near-surface layers of the cometary atmosphere. I. A spherical nucleus

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Sublimation coefficient of water ice under simulated cometary-like conditions

Cited by 56 publications

References 13 publications

OSIRIS observations of meter-sized exposures of H2O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments

OSIRIS observations of meter-sized exposures of H2O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments

A Model of Heat and Mass Transfer in a Porous Cometary Nucleus Based on a Kinetic Treatment of Mass Flow

Direct statistical simulation of the near-surface layers of the cometary atmosphere. I. A spherical nucleus

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Product

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OSIRIS observations of meter-sized exposures of H₂O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments

OSIRIS observations of meter-sized exposures of H₂O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments