scholarly journals Ceres’ partial differentiation: undifferentiated crust mixing with a water-rich mantle

2020 ◽  
Vol 633 ◽  
pp. A117 ◽  
Author(s):  
Wladimir Neumann ◽  
Ralf Jaumann ◽  
Julie Castillo-Rogez ◽  
Carol A. Raymond ◽  
Christopher T. Russell
Keyword(s):  
Thermal Evolution ◽  
Kuiper Belt ◽  
Radioactive Decay ◽  
Thermal Conditions ◽  
Asteroid Belt ◽  
Final Size ◽  
Water Ice ◽  
Modeled Structure ◽  
Internal States ◽  
And Migration

Aims. We model thermal evolution and water-rock differentiation of small ice-rock objects that accreted at different heliocentric distances, while also considering migration into the asteroid belt for Ceres. We investigate how water-rock separation and various cooling processes influence Ceres’ structure and its thermal conditions at present. We also draw conclusions about the presence of liquids and the possibility of cryovolcanism. Methods. We calculated energy balance in bodies heated by radioactive decay and compaction-driven water-rock separation in a three-component dust-water/ice-empty pores mixture, while also taking into consideration second-order processes, such as accretional heating, hydrothermal circulation, and ocean or ice convection. Calculations were performed for varying accretion duration, final size, surface temperature, and dust/ice ratio to survey the range of possible internal states for precursors of Ceres. Subsequently, the evolution of Ceres was considered in five sets of simulated models, covering different accretion and evolution orbits and dust/ice ratios. Results. We find that Ceres’ precursors in the inner solar system could have been both wet and dry, while in the Kuiper belt, they retain the bulk of their water content. For plausible accretion scenarios, a thick primordial crust may be retained over several Gyr, following a slow differentiation within a few hundreds of Myr, assuming an absence of destabilizing impacts. The resulting thermal conditions at present allow for various salt solutions at depths of ≲10 km. The warmest present subsurface is obtained for an accretion in the Kuiper belt and migration to the present orbit. Conclusions. Our results indicate that Ceres’ material could have been aqueously altered on small precursors. The modeled structure of Ceres suggests that a liquid layer could still be present between the crust and the core, which is consistent with Dawn observations and, thus, suggests accretion in the Kuiper belt. While the crust stability calculations indicate crust retention, the convection analysis and interior evolution imply that the crust could still be evolving.

scholarly journals Exploring the conditions for forming cold gas giants through planetesimal accretion

2019 ◽  
Vol 631 ◽  
pp. A70 ◽  
Author(s):  
Anders Johansen ◽  
Bertram Bitsch
Keyword(s):  
Kuiper Belt ◽  
Oort Cloud ◽  
Asteroid Belt ◽  
Nominal Model ◽  
The Core ◽  
And Migration ◽  
The Masses ◽  
Core Accretion ◽  
Cold Gas ◽  
Protoplanetary Discs

The formation of cold gas giants similar to Jupiter and Saturn in orbit and mass is a great challenge for planetesimal-driven core accretion models because the core growth rates far from the star are low. Here we model the growth and migration of single protoplanets that accrete planetesimals and gas. We integrated the core growth rate using fits in the literature to N-body simulations, which provide the efficiency of accreting the planetesimals that a protoplanet migrates through. We take into account three constraints from the solar system and from protoplanetary discs: (1) the masses of the terrestrial planets and the comet reservoirs in Neptune’s scattered disc and the Oort cloud are consistent with a primordial planetesimal population of a few Earth masses per AU, (2) evidence from the asteroid belt and the Kuiper belt indicates that the characteristic planetesimal diameter is 100 km, and (3) observations of protoplanetary discs indicate that the dust is stirred by weak turbulence; this gas turbulence also excites the inclinations of planetesimals. Our nominal model built on these constraints results in maximum protoplanet masses of 0.1 Earth masses. Ignoring constraint (1) above, we show that even a planetesimal population of 1000 Earth masses, corresponding to 50 Earth masses per AU, fails to produce cold gas giants (although it successfully forms hot and warm gas giants). We conclude that a massive planetesimal reservoir is in itself insufficient to produce cold gas giants. The formation of cold gas giants by planetesimal accretion additionally requires that planetesimals are small and that the turbulent stirring is very weak, thereby violating all three above constraints.

scholarly journals Organic matter and water from asteroid Itokawa

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Q. H. S. Chan ◽  
A. Stephant ◽  
I. A. Franchi ◽  
X. Zhao ◽  
R. Brunetto ◽  
...  
Keyword(s):  
Organic Matter ◽  
Solar System ◽  
Parent Body ◽  
Asteroid Belt ◽  
True Nature ◽  
Water Ice ◽  
Nanocrystalline Graphite ◽  
Terrestrial Water ◽  
Solar System Bodies ◽  
Small Dust

AbstractUnderstanding the true nature of extra-terrestrial water and organic matter that were present at the birth of our solar system, and their subsequent evolution, necessitates the study of pristine astromaterials. In this study, we have studied both the water and organic contents from a dust particle recovered from the surface of near-Earth asteroid 25143 Itokawa by the Hayabusa mission, which was the first mission that brought pristine asteroidal materials to Earth’s astromaterial collection. The organic matter is presented as both nanocrystalline graphite and disordered polyaromatic carbon with high D/H and 15N/14N ratios (δD =  + 4868 ± 2288‰; δ15N =  + 344 ± 20‰) signifying an explicit extra-terrestrial origin. The contrasting organic feature (graphitic and disordered) substantiates the rubble-pile asteroid model of Itokawa, and offers support for material mixing in the asteroid belt that occurred in scales from small dust infall to catastrophic impacts of large asteroidal parent bodies. Our analysis of Itokawa water indicates that the asteroid has incorporated D-poor water ice at the abundance on par with inner solar system bodies. The asteroid was metamorphosed and dehydrated on the formerly large asteroid, and was subsequently evolved via late-stage hydration, modified by D-enriched exogenous organics and water derived from a carbonaceous parent body.

scholarly journals Water Ice on the Satellite of Kuiper Belt Object 2003 EL 61

2006 ◽  
Vol 640 (1) ◽  
pp. L87-L89 ◽  
Author(s):  
K. M Barkume ◽  
M. E. Brown ◽  
E. L. Schaller
Keyword(s):  
Kuiper Belt ◽  
Kuiper Belt Object ◽  
Water Ice

Crystalline water ice on the Kuiper belt object (50000) Quaoar

Nature ◽  
2004 ◽  
Vol 432 (7018) ◽  
pp. 731-733 ◽  
Author(s):  
David C. Jewitt ◽  
Jane Luu
Keyword(s):  
Kuiper Belt ◽  
Kuiper Belt Object ◽  
Water Ice ◽  
Crystalline Water

scholarly journals Parameterisations of interior properties of rocky planets

2020 ◽  
Vol 638 ◽  
pp. A129 ◽  
Author(s):  
Lena Noack ◽  
Marine Lasbleis
Keyword(s):  
Thermodynamic Properties ◽  
Scaling Laws ◽  
Thermal State ◽  
Thermal Evolution ◽  
Pure Water ◽  
Mass Composition ◽  
Temperature Profiles ◽  
Interior Structure ◽  
Water Ice ◽  
Simple Mass

Context. Observations of Earth-sized exoplanets are mostly limited to information on their masses and radii. Simple mass-radius relationships have been developed for scaled-up versions of Earth or other planetary bodies such as Mercury and Ganymede, as well as for one-material spheres made of pure water(-ice), silicates, or iron. However, they do not allow a thorough investigation of composition influences and thermal state on a planet’s interior structure and properties. Aims. In this work, we investigate the structure of a rocky planet shortly after formation and at later stages of thermal evolution assuming the planet is differentiated into a metal core and a rocky mantle (consisting of Earth-like minerals, but with a variable iron content). Methods. We derived possible initial temperature profiles after the accretion and magma ocean solidification. We then developed parameterisations for the thermodynamic properties inside the core depending on planet mass, composition, and thermal state. Results. We provide the community with robust scaling laws for the interior structure, temperature profiles, and core- and mantle-averaged thermodynamic properties for planets composed of Earth’s main minerals but with variable compositions of iron and silicates. Conclusions. The scaling laws make it possible to investigate variations in thermodynamic properties for different interior thermal states in a multitude of applications such as deriving mass-radius scaling laws or estimating magnetic field evolution and core crystallisation for rocky exoplanets.

Thermal Physics of Cometary Nuclei

2020 ◽  
Author(s):  
Dina Prialnik
Keyword(s):  
Solar Energy ◽  
Thermal Emission ◽  
Thermal Evolution ◽  
Internal Heat ◽  
Thermal Inertia ◽  
Skin Depth ◽  
Physical Models ◽  
The Sun ◽  
Cometary Nuclei ◽  
Water Ice

Cometary nuclei, as small, spinning, ice-rich objects revolving around the sun in eccentric orbits, are powered and activated by solar radiation. Far from the sun, most of the solar energy is reradiated as thermal emission, whereas close to the sun, it is absorbed by sublimation of ice. Only a small fraction of the solar energy is conducted into the nucleus interior. The rate of heat conduction determines how deep and how fast this energy is dissipated. The conductivity of cometary nuclei, which depends on their composition and porosity, is estimated based on vastly different models ranging from very simple to extremely complex. The characteristic response to heating is determined by the skin depth, the thermal inertia, and the thermal diffusion timescale, which depend on the comet’s structure and dynamics. Internal heat sources include the temperature-dependent crystallization of amorphous water ice, which becomes important at temperatures above about 130 K; occurs in spurts; and releases volatiles trapped in the ice. These, in turn, contribute to heat transfer by advection and by phase transitions. Radiogenic heating resulting from the decay of short-lived unstable nuclei such as 26Al heats the nucleus shortly after formation and may lead to compositional alterations. The thermal evolution of the nucleus is described by thermo-physical models that solve mass and energy conservation equations in various geometries, sometimes very complicated, taking into account self-heating. Solutions are compared with actual measurements from spacecraft, mainly during the Rosetta mission, to deduce the thermal properties of the nucleus and decipher its activity pattern.

Simultaneous resolution of reactive radioactive decay, non-isothermal flow, and migration with application to the performance assessment for HLW repositories

2010 ◽  
Vol 98 (6) ◽  
Author(s):  
R. Juncosa ◽  
I. Font ◽  
J. Delgado
Keyword(s):  
Ion Exchange ◽  
Radioactive Decay ◽  
Chemical Species ◽  
High Level Waste ◽  
Chemical Components ◽  
Clay Material ◽  
Decay Series ◽  
And Migration ◽  
High Level ◽  
Radioactive Species

AbstractRadioactive decay is an important subject to take into account when studying the thermo-hydro-dynamic behavior of the buffer clay material used in the containment of radioactive waste. The modern concepts for the multibarrier design of a repository of high level waste in deep geologic formations consider that once canisters have failed, the buffer clay material must ensure the retention and/or delay of radionuclides within the time framework given in the assessment studies. Within the clay buffer, different chemical species are retarded/fixed according to several physicochemical processes (ion exchange, surface complexation, precipitation, matrix diffusion, ...) but typical approaches do not consider the eventuality that radioactive species change their chemical nature (The radioactive decay of an element takes place independently of the phase (aqueous, solid or gaseous) to which it belongs. This means that, in terms of radionuclide fixation, some geochemical processes will be effective scavengers (for instance mineral precipitation of crystal growth) while others will not (for instance ion exchange and/or sorption).In this contribution we present a reactive radioactive decay model of any number of chemical components including those that belong to decay series. The model, which is named FLOW-DECAY, also takes into account flow and isotopic migration and it has been applied considering a hypothetical model scenario provided by the project ENRESA 2000 and direct comparison with the results generated by the probabilistic code GoldSim. Results indicate that FLOW-DECAY may simulate the decay processes in a similar way that GoldSim, being the differences related to factors associated to code architecture.

scholarly journals Long-term evolution of small icy bodies of the Solar System

2009 ◽  
Vol 5 (S263) ◽  
pp. 121-125 ◽  
Author(s):  
Dina Prialnik
Keyword(s):  
Kuiper Belt ◽  
Radioactive Decay ◽  
Main Belt ◽  
Kuiper Belt Object ◽  
Amorphous Ice ◽  
The Core ◽  
Porous Core ◽  
Term Evolution ◽  
Highly Porous

AbstractDetailed evolutionary calculations spanning 4.6 × 109 yr are presented for (a) a model representing main-belt comet 133P/Elst-Pizarro, considering different initial mixtures of ices and dust, and (b) a Kuiper Belt object heated by radioactive decay, growing in size from an initial radius of 10 km to a final 250 km.It is shown that for the main-belt comet only crystalline H2O ice may survive in the interior of the nucleus, and may be found at depths ranging from ~50 to 150 m. Other volatiles will be completely lost. For the large Kuiper Belt object, evaporation and flow of water and vapor gradually remove the water from the core and the final (present) structure is differentiated, with a rocky, highly porous core of 80 km radius. Outside the core, due to refreezing of water vapor, a compact, ice-rich layer forms, a few tens of km thick. The amorphous ice is preserved in an outer layer about 20 km thick.

Cryosurgery: Analysis and Experimentation of Cryoprobes in Phase Changing Media

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Avraham Shitzer
Keyword(s):  
Thermal Conditions ◽  
Blood Perfusion ◽  
Optimal Placement ◽  
Tissue Destruction ◽  
Final Size ◽  
Israel Institute ◽  
Thaw Cycle ◽  
Institute Of Technology

This article presents a retrospective of work performed at the Technion, Israel Institute of Technology, over the last 3-odd decades. Results of analytical and numerical studies are presented briefly as well as in vitro and in vivo experimental data and their comparison to the derived results. Studies include the analysis of both the direct (Stefan) and the inverse-Stefan phase-change heat transfer problems in a tissue-simulating medium (gel) by the application of both surface and insertion cryoprobes. The effects of blood perfusion and metabolic heat generation rates on the advancement of the freezing front are discussed. The simultaneous operation of needle cryoprobes in a number of different configurations and the effects of a thermally significant blood vessel in the vicinity of the cryoprobe are also presented. Typical results demonstrate that metabolic rate in the yet nonfrozen tissue, will have only minor effects on the advancement of the frozen front. Capillary blood perfusion, on the other hand, does affect the course of change of the temperature distribution, hindering, as it is increased, the advancement of the frozen front. The volumes enclosed by the “lethal” isotherm (assumed as −40°C), achieve most of their final size in the first few minutes of operation, thus obviating the need for prolonged applications. Volumes occupied by this lethal isotherm were shown to be rather small. Thus, after 10 min of operation, these volumes will occupy only about 6% (single probe), 6–11% (two probes, varying distances apart), and 6–15% (three probes, different placement configurations), relative to the total frozen volume. For cryosurgery to become the treatment-of-choice, much more work will be required to cover the following issues: (1) A clear cut understanding and definition of the tissue-specific thermal conditions that are required to ensure the complete destruction of a tissue undergoing a controlled cryosurgical process. (2) Comprehensive analyses of the complete freeze/thaw cycle(s) and it effects on the final outcome. (3) Improved technical means to control the temperature variations of the cryoprobe to achieve the desired thermal conditions required for tissue destruction. (4) Improvement in the pretreatment design process to include optimal placement schemes of multiprobes and their separate and specific operation. (5) Understanding the effects of thermally significant blood vessels, and other related thermal perturbations, which are situated adjacent to, or even within, the tissue volume to be treated.

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