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Dina Prialnik - One of the best experts on this subject based on the ideXlab platform.
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the effect of internal inhomogeneity on the activity of Comet Nuclei application to Comet 67p churyumov gerasimenko
Icarus, 2010Co-Authors: Eric D Rosenberg, Dina PrialnikAbstract:Abstract We present thermal evolution calculations of inhomogeneous asymmetric initial configurations of a spherical model of Comet 67P/Churyumov–Gerasimenko, using a fully 3-dimensional numerical code. The initial composition is amorphous H 2 O ice and dust, in a “layered-pile” configuration, where layers differing in ice/dust ratio and thermal properties extend over a fraction of the surface area and about 10 m in depth and may overlap. We analyze the effect of one such layer, as well as the combined effect of many layers, randomly distributed. We find that internal inhomogeneities affect both the surface temperature and the activity pattern of the Comet. In particular, they may lead to outbursts at large heliocentric distances and also to activity on the night-side of the nucleus. The rates of ablation and depths of dust mantle and crystalline ice outer layer as functions of longitude and latitude are shown to be affected as well.
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thermal and chemical evolution of Comet Nuclei and kuiper belt objects
oeec, 2009Co-Authors: Dina Prialnik, Gal Sarid, Eric D Rosenberg, Rainer MerkAbstract:The structure and composition of Comet Nuclei are mainly altered during two short phases that are separated by a very long hibernation phase. Early evolution—during and immediately after formation—is the result of heating caused by radioactive decay, the most important source being 26Al. Several studies are reviewed, dealing with evolution throughout this phase, calculated by means of 1-D numerical codes that solve the heat and mass balance equations on a fixed spherically symmetric grid. It is shown that, depending on parameters, the interior may reach temperatures above the melting point of water. The models thus suggest that Comets are likely to lose the ices of very volatile species during early evolution; ices of less volatile species are retained in the cold subsurface layer. As the initially amorphous ice is shown to crystallize in the interior, some objects may also lose part of the volatiles trapped in amorphous ice. Generally, the outer layers are far less affected than the inner part, resulting in a stratified composition and altered porosity distribution. The second phase of evolution occurs when Comet Nuclei are deflected into the inner solar system and is dominated by the effect of solar radiation. Now the outer layers are those mostly affected, undergoing crystallization, loss of volatiles, and significant structural changes. If any part of a Comet nucleus should retain its pristine structure and composition, it would be well below the surface and also well above the core.
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section iii evolution of Nuclei thermal and chemical evolution of Comet Nuclei and kuiper belt objects
2008Co-Authors: Dina Prialnik, Gal Sarid, Eric D Rosenberg, Rainer MerkAbstract:The structure and composition of Comet Nuclei are mainly altered during two short phases that are separated by a very long hibernation phase. Early evolution—during and immediately after formation—is the result of heating caused by radioactive decay, the most important source being 26Al. Several studies are reviewed, dealing with evolution throughout this phase, calculated by means of 1-D numerical codes that solve the heat and mass balance equations on a fixed spherically symmetric grid. It is shown that, depending on parameters, the interior may reach temperatures above the melting point of water. The models thus suggest that Comets are likely to lose the ices of very volatile species during early evolution; ices of less volatile species are retained in the cold subsurface layer. As the initially amorphous ice is shown to crystallize in the interior, some objects may also lose part of the volatiles trapped in amorphous ice. Generally, the outer layers are far less affected than the inner part, resulting in a stratified composition and altered porosity distribution. The second phase of evolution occurs when Comet Nuclei are deflected into the inner solar system and is dominated by the effect of solar radiation. Now the outer layers are those mostly affected, undergoing crystallization, loss of volatiles, and significant structural changes. If any part of a Comet nucleus should retain its pristine structure and composition, it would be well below the surface and also well above the core.
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dust mantle formation and thermal evolution of Comet Nuclei using a 3 d numerical model
LPICo, 2008Co-Authors: Eric D Rosenberg, Dina PrialnikAbstract:Spacecraft observations of Comet Nuclei at close range have revealed dust covered surfaces with eventual patches of exposed ice (e.g., A’Hearn et al. [2]). Despite the insulating dust mantle, Cometary activity appears to be closely correlated with heliocentric distance, and even with the daily local position of the sun. This indicates that the dust mantle must be thin and probably frequently regenerated. The question of the dust mantle thickness is of utmost importance for Comet 67P/ChuryumovGerasimenko, the target of the Rosetta mission. We adopt the orbital and spin parameters of the Comet in order to investigate in detail dust mantle formation on the surface of the nucleus. The effect of different processes and thermal conductivity values is estimated. We find a strong dependence of the dust mantle thickness on thermal conductivity.
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modeling the structure and activity of Comet Nuclei
come, 2004Co-Authors: Dina Prialnik, J Benkhoff, M PodolakAbstract:Numerical simulation of the structure and evolution of a Comet nucleus is reviewed from both the mathematical and the physical point of view. Various mathematical procedures and approximations are discussed, and different attempts to model the physical characteristics of Cometary material, such as thermal conductivity, permeability to gas flow, drag of dust grains, and dust mantling, are described. The evolution and activity of Comets is shown to depend on different classes of parameters: defining parameters, such as size and orbit; structural parameters, such as porosity and composition; and initial parameters, such as temperature and live radioisotope content. Despite the large number of parameters, general conclusions or common features appear to emerge from the numerous model calculations — for different Comets — performed to date. Thus, the stratified structure of Comet Nuclei, volatile depletion, and the role of crystallization of ice in Cometary outbursts are discussed.
Giovanni Carraro - One of the best experts on this subject based on the ideXlab platform.
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surface composition and dynamical evolution of two retrograde objects in the outer solar system 2008 yb3 and 2005 vd
Astronomy and Astrophysics, 2013Co-Authors: N Pinillaalonso, A Alvarezcandal, M D Melita, V Lorenzi, J Licandro, J M Carvano, D Lazzaro, Giovanni CarraroAbstract:Most of the objects in the trans-Neptunian belt (TNb) and related populations move in prograde orbits with low eccentricity and inclination. However, the list of icy minor bodies moving in orbits with an inclination above 40 has increased in recent years. The origin of these bodies, and in particular of those objects in retrograde orbits, is not well determined, and di erent scenarios are considered, depending on their inclination and perihelion. In this paper, we present new observational and dynamical data of two objects in retrograde orbits, 2008 YB3 and 2005 VD. We find that the surface of these extreme objects is depleted of ices and does not contain the ‘ultra-red’ matter typical of some Centaurs. Despite small di erences, these objects share common colors and spectral characteristics with the Trojans, Comet Nuclei, and the group of grey Centaurs. All of these populations are supposed to be covered by a mantle of dust responsible for their reddish- to neutral-color. To investigate if the surface properties and dynamical evolution of these bodies are related, we integrate their orbits for 10 8 years to the past. We find a remarkable di erence in their dynamical evolutions: 2005 VD’s evolution is dominated by a Kozai resonance with planet Jupiter while that of 2008 YB3 is dominated by close encounters with planets Jupiter and Saturn. Our models suggest that the immediate site of provenance of 2005 VD is the in the Oort cloud, whereas for 2008 YB3 it is in the trans-Neptunian region. Additionally, the study of their residence time shows that 2005 VD has spent a larger lapse of time moving in orbits in the region of the giant planets than 2008 YB3. Together with the small di erences in color between these two objects, with 2005 VD being more neutral than 2008 YB3, this fact suggests that the surface of 2005 VD has su ered a higher degree of processing, probably related to Cometary activity episodes.
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surface composition and dynamical evolution of two retrograde objects in the outer solar system 2008 yb3 and 2005 vd
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: N Pinillaalonso, A Alvarezcandal, M D Melita, V Lorenzi, J Licandro, J M Carvano, D Lazzaro, Giovanni CarraroAbstract:Most of the objects in the trans-Neptunian belt (TNb) and related populations move in prograde orbits with low eccentricity and inclination. However, the list of icy minor bodies moving in orbits with an inclination above 40 deg. has increased in recent years. The origin of these bodies, and in particular of those objects in retrograde orbits, is not well determined, and different scenarios are considered. In this paper, we present new observational and dynamical data of two objects in retrograde orbits, 2008 YB3 and 2005 VD. We find that the surface of these extreme objects is depleted of ices and does not contain the 'ultra-red' matter typical of some Centaurs. Despite small differences, these objects share common colors and spectral characteristics with the Trojans, Comet Nuclei, and the group of grey Centaurs. All of these populations are supposed to be covered by a mantle of dust responsible for their reddish- to neutral-color. To investigate if the surface properties and dynamical evolution of these bodies are related, we integrate their orbits for 10^(8) years to the past. We find a remarkable difference in their dynamical evolutions: 2005 VD' s evolution is dominated by a Kozai resonance with planet Jupiter while that of 2008 YB3 is dominated by close encounters with planets Jupiter and Saturn. Our models suggest that the immediate site of provenance of 2005 VD is the in the Oort cloud, whereas for 2008 YB3 it is in the trans-Neptunian region. Additionally, the study of their residence time shows that 2005 VD has spent a larger lapse of time moving in orbits in the region of the giant planets than 2008 YB3. Together with the small differences in color between these two objects, with 2005 VD being more neutral than 2008 YB3, this fact suggests that the surface of 2005 VD has suffered a higher degree of processing, probably related to Cometary activity episodes.
M Podolak - One of the best experts on this subject based on the ideXlab platform.
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modeling the structure and activity of Comet Nuclei
come, 2004Co-Authors: Dina Prialnik, J Benkhoff, M PodolakAbstract:Numerical simulation of the structure and evolution of a Comet nucleus is reviewed from both the mathematical and the physical point of view. Various mathematical procedures and approximations are discussed, and different attempts to model the physical characteristics of Cometary material, such as thermal conductivity, permeability to gas flow, drag of dust grains, and dust mantling, are described. The evolution and activity of Comets is shown to depend on different classes of parameters: defining parameters, such as size and orbit; structural parameters, such as porosity and composition; and initial parameters, such as temperature and live radioisotope content. Despite the large number of parameters, general conclusions or common features appear to emerge from the numerous model calculations — for different Comets — performed to date. Thus, the stratified structure of Comet Nuclei, volatile depletion, and the role of crystallization of ice in Cometary outbursts are discussed.
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a quasi 3d model for the evolution of shape and temperature distribution of Comet Nuclei application to Comet 46p wirtanen
New Astronomy, 2003Co-Authors: Merav Cohen, Dina Prialnik, M PodolakAbstract:Abstract We introduce a quasi 3-D thermal evolution model for a spherical Comet nucleus, which takes into account the diurnal and latitudinal variation of the solar flux, but neglects lateral heat conduction, which is shown to be insignificant. Comparing this model with the ‘fast-rotator’, evenly heated nucleus model, we show that, for long-term calculations of the evolution of the interior, the latter provides a good approximation. The 3-D model is applied to Comet 46P/Wirtanen : yielding the distribution of temperature and water production rate over the nucleus surface. A very good agreement with observations is obtained for the integrated production rate. The model is also used in order to derive the change of shape due to uneven erosion. Two cases are considered for different inclination angles of the spin axis; it is concluded that the evolved shape depends strongly on the obliquity of the Comet’s spin axis.
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changes in the structure of Comet Nuclei due to radioactive heating
Space Science Reviews, 1999Co-Authors: Dina Prialnik, M PodolakAbstract:The initial structure of a Comet nucleus is most probably a homogeneous, porous, finegrained mixture of dust and ices, predominantly water. The water ice is presumably amorphous and includes considerable fractions of occluded gases. This structure undergoes significant changes during the early evolution of the nucleus at large heliocentric distances, due to internal radiogenic heating. Structural changes occur mainly as a result of gas flow through the porous medium: the gas pressure that builds up in the interior is capable of breaking the fragile structure and altering the pore sizes and porosity. These effects are modeled and followed numerically, testing a large number of parameters.
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radioactive heating of porous Comet Nuclei
Icarus, 1995Co-Authors: Dina Prialnik, M PodolakAbstract:Abstract Radioactive heating is the main energy source of Comets residing in the distant parts of the Solar System. It should determine whether liquid water could have existed in Comets and whether Comets, presumably formed of amorphous ice, could have retained the ice, at least partly, in this pristine form. Thermal evolution calculations of relatively large (over 10 km in radius), porous Comet Nuclei are performed for many different initial parameter combinations. The radioisotopes considered are 40 K, 232 Th, 235 U, and 238 U, in meteoritic abundances, as well as 26 Al, in various initial abundances. We allow for heat conduction through the ice-dust matrix, as well as advection by flowing gases. Crystallization of the amorphous ice accompanied by release of occluded gases, and sublimation/condensation from/ onto the pore walls are taken into account. We find that porous Comet Nuclei may emerge from the long-term evolution in three different configurations, depending on the thermal conductivity, porous structure, radius, etc.: (a) preserving their pristine structure throughout; (b) almost completely crystallized (except for a relatively thin outer layer), and (c) having a crystallized core, a layer of frozen gas (originally occluded in the amorphous ice) and an outer layer of unaltered pristine material. Liquid cores may be obtained only if the porosity is negligible. The extent of such cores and the length of time during which they remain liquid are again determined by initial conditions, as well as by physical properties of the ice. If, in addition to the very low porosity, the conductivity were extremely low, it should be possible to have both an extended liquid core, for a considerable period of time, and an outer layer of significant thickness that has retained its original pristine structure.
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on pore size and fracture in gas laden Comet Nuclei
Icarus, 1993Co-Authors: Dina Prialnik, M Podolak, A Barnun, Uzi Egozi, Yuval GreenzweigAbstract:Abstract We have followed the evolution of a porous Comet nucleus made of gas-laden amorphous ice in the orbit of P/Halley. The gas is released from the ice as the ice crystallizes and flows through the porous medium, driven by pressure and temperature gradients. When the pressure gradient is sufficiently high to violate mechanical equilibrium—in view of the low tensile strength of Cometary ice—the pores are allowed to widen, so as to release the pressure and regain stability. The criterion for pore widening is taken to be that of fracture of brittle material under tensile stress. The parameters of the problem are: the tensile strength of the ice (10 4 -10 6 dyn/cm 2 ), the gas content (5-10%), and the resistance of the ice to progressive pore widening (cracking) as a function of pore size. We find that, depending on these parameters, pores (tortuous capillaries) of several millimeters to a few centimeters open throughout the crystalline ice layer. Under extreme conditions, no stable configuration is obtained; namely, tensile failure occurs. Such a situation is interpreted as an explosion; it is found to occur at a depth of 120 m and at a heliocentric distance of ∼12 AU. Under milder conditions, very wide channels open up—over 1 m in diameter—which may serve as a vent for gas drainage that may appear as a jet.
J Licandro - One of the best experts on this subject based on the ideXlab platform.
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surface composition and dynamical evolution of two retrograde objects in the outer solar system 2008 yb3 and 2005 vd
Astronomy and Astrophysics, 2013Co-Authors: N Pinillaalonso, A Alvarezcandal, M D Melita, V Lorenzi, J Licandro, J M Carvano, D Lazzaro, Giovanni CarraroAbstract:Most of the objects in the trans-Neptunian belt (TNb) and related populations move in prograde orbits with low eccentricity and inclination. However, the list of icy minor bodies moving in orbits with an inclination above 40 has increased in recent years. The origin of these bodies, and in particular of those objects in retrograde orbits, is not well determined, and di erent scenarios are considered, depending on their inclination and perihelion. In this paper, we present new observational and dynamical data of two objects in retrograde orbits, 2008 YB3 and 2005 VD. We find that the surface of these extreme objects is depleted of ices and does not contain the ‘ultra-red’ matter typical of some Centaurs. Despite small di erences, these objects share common colors and spectral characteristics with the Trojans, Comet Nuclei, and the group of grey Centaurs. All of these populations are supposed to be covered by a mantle of dust responsible for their reddish- to neutral-color. To investigate if the surface properties and dynamical evolution of these bodies are related, we integrate their orbits for 10 8 years to the past. We find a remarkable di erence in their dynamical evolutions: 2005 VD’s evolution is dominated by a Kozai resonance with planet Jupiter while that of 2008 YB3 is dominated by close encounters with planets Jupiter and Saturn. Our models suggest that the immediate site of provenance of 2005 VD is the in the Oort cloud, whereas for 2008 YB3 it is in the trans-Neptunian region. Additionally, the study of their residence time shows that 2005 VD has spent a larger lapse of time moving in orbits in the region of the giant planets than 2008 YB3. Together with the small di erences in color between these two objects, with 2005 VD being more neutral than 2008 YB3, this fact suggests that the surface of 2005 VD has su ered a higher degree of processing, probably related to Cometary activity episodes.
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surface composition and dynamical evolution of two retrograde objects in the outer solar system 2008 yb3 and 2005 vd
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: N Pinillaalonso, A Alvarezcandal, M D Melita, V Lorenzi, J Licandro, J M Carvano, D Lazzaro, Giovanni CarraroAbstract:Most of the objects in the trans-Neptunian belt (TNb) and related populations move in prograde orbits with low eccentricity and inclination. However, the list of icy minor bodies moving in orbits with an inclination above 40 deg. has increased in recent years. The origin of these bodies, and in particular of those objects in retrograde orbits, is not well determined, and different scenarios are considered. In this paper, we present new observational and dynamical data of two objects in retrograde orbits, 2008 YB3 and 2005 VD. We find that the surface of these extreme objects is depleted of ices and does not contain the 'ultra-red' matter typical of some Centaurs. Despite small differences, these objects share common colors and spectral characteristics with the Trojans, Comet Nuclei, and the group of grey Centaurs. All of these populations are supposed to be covered by a mantle of dust responsible for their reddish- to neutral-color. To investigate if the surface properties and dynamical evolution of these bodies are related, we integrate their orbits for 10^(8) years to the past. We find a remarkable difference in their dynamical evolutions: 2005 VD' s evolution is dominated by a Kozai resonance with planet Jupiter while that of 2008 YB3 is dominated by close encounters with planets Jupiter and Saturn. Our models suggest that the immediate site of provenance of 2005 VD is the in the Oort cloud, whereas for 2008 YB3 it is in the trans-Neptunian region. Additionally, the study of their residence time shows that 2005 VD has spent a larger lapse of time moving in orbits in the region of the giant planets than 2008 YB3. Together with the small differences in color between these two objects, with 2005 VD being more neutral than 2008 YB3, this fact suggests that the surface of 2005 VD has suffered a higher degree of processing, probably related to Cometary activity episodes.
A Alvarezcandal - One of the best experts on this subject based on the ideXlab platform.
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surface composition and dynamical evolution of two retrograde objects in the outer solar system 2008 yb3 and 2005 vd
Astronomy and Astrophysics, 2013Co-Authors: N Pinillaalonso, A Alvarezcandal, M D Melita, V Lorenzi, J Licandro, J M Carvano, D Lazzaro, Giovanni CarraroAbstract:Most of the objects in the trans-Neptunian belt (TNb) and related populations move in prograde orbits with low eccentricity and inclination. However, the list of icy minor bodies moving in orbits with an inclination above 40 has increased in recent years. The origin of these bodies, and in particular of those objects in retrograde orbits, is not well determined, and di erent scenarios are considered, depending on their inclination and perihelion. In this paper, we present new observational and dynamical data of two objects in retrograde orbits, 2008 YB3 and 2005 VD. We find that the surface of these extreme objects is depleted of ices and does not contain the ‘ultra-red’ matter typical of some Centaurs. Despite small di erences, these objects share common colors and spectral characteristics with the Trojans, Comet Nuclei, and the group of grey Centaurs. All of these populations are supposed to be covered by a mantle of dust responsible for their reddish- to neutral-color. To investigate if the surface properties and dynamical evolution of these bodies are related, we integrate their orbits for 10 8 years to the past. We find a remarkable di erence in their dynamical evolutions: 2005 VD’s evolution is dominated by a Kozai resonance with planet Jupiter while that of 2008 YB3 is dominated by close encounters with planets Jupiter and Saturn. Our models suggest that the immediate site of provenance of 2005 VD is the in the Oort cloud, whereas for 2008 YB3 it is in the trans-Neptunian region. Additionally, the study of their residence time shows that 2005 VD has spent a larger lapse of time moving in orbits in the region of the giant planets than 2008 YB3. Together with the small di erences in color between these two objects, with 2005 VD being more neutral than 2008 YB3, this fact suggests that the surface of 2005 VD has su ered a higher degree of processing, probably related to Cometary activity episodes.
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surface composition and dynamical evolution of two retrograde objects in the outer solar system 2008 yb3 and 2005 vd
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: N Pinillaalonso, A Alvarezcandal, M D Melita, V Lorenzi, J Licandro, J M Carvano, D Lazzaro, Giovanni CarraroAbstract:Most of the objects in the trans-Neptunian belt (TNb) and related populations move in prograde orbits with low eccentricity and inclination. However, the list of icy minor bodies moving in orbits with an inclination above 40 deg. has increased in recent years. The origin of these bodies, and in particular of those objects in retrograde orbits, is not well determined, and different scenarios are considered. In this paper, we present new observational and dynamical data of two objects in retrograde orbits, 2008 YB3 and 2005 VD. We find that the surface of these extreme objects is depleted of ices and does not contain the 'ultra-red' matter typical of some Centaurs. Despite small differences, these objects share common colors and spectral characteristics with the Trojans, Comet Nuclei, and the group of grey Centaurs. All of these populations are supposed to be covered by a mantle of dust responsible for their reddish- to neutral-color. To investigate if the surface properties and dynamical evolution of these bodies are related, we integrate their orbits for 10^(8) years to the past. We find a remarkable difference in their dynamical evolutions: 2005 VD' s evolution is dominated by a Kozai resonance with planet Jupiter while that of 2008 YB3 is dominated by close encounters with planets Jupiter and Saturn. Our models suggest that the immediate site of provenance of 2005 VD is the in the Oort cloud, whereas for 2008 YB3 it is in the trans-Neptunian region. Additionally, the study of their residence time shows that 2005 VD has spent a larger lapse of time moving in orbits in the region of the giant planets than 2008 YB3. Together with the small differences in color between these two objects, with 2005 VD being more neutral than 2008 YB3, this fact suggests that the surface of 2005 VD has suffered a higher degree of processing, probably related to Cometary activity episodes.