MODELING OF THE THERMAL-BEHAVIOR AND OF THE CHEMICAL DIFFERENTIATION OF COMETARY NUCLEI

被引:116
作者
ESPINASSE, S [1 ]
KLINGER, J [1 ]
RITZ, C [1 ]
SCHMITT, B [1 ]
机构
[1] CNRS,GLACIOL & GEOPHYS ENVIRONNEMENT LAB,BP 96,F-38402 ST MARTIN DHERES,FRANCE
关键词
D O I
10.1016/0019-1035(91)90058-2
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Taking into account the low values of average density reported for Comet P/Halley, a model of a porous comet nucleus has been developed. The model includes heat conduction through the solid matrix and heat and mass transfers due to the vapor phase circulating in the pore system. Sublimation and recondensation of volatile species within the nucleus as well as water ice crystallization are represented according to experimental results on the evolution of ice mixtures with time and temperature. The model is based on the resolution of two symmetric diffusion equations through the whole nucleus, one describing the transport of matter and the other the transport of heat. These equations are linked by the source term. The sensible heat term due to gas advection is also integrated into the heat diffusion equation. The calculations are performed for comets on the orbits of P/Halley and P/Churyumov-Gerasimenko. Different nucleus compositions with ice mixtures containing H2O and CO or CO2 are investigated. The consequences of the amorphous to crystalline phase transition of water ice on the thermal profiles and on the evolution of the composition of the nucleus are studied. Results are presented on the evolution of the stratigraphy of the nucleus and of the production rates of CO, CO2, and H2O as a function of the heliocentric distance. Several phenomena are evidenced such as the depletion of volatiles in the subsurface layers and their enrichment in deeper layers. The important role of CO and CO2 in controlling the propagation of the phase transition is emphasized. The relation between the composition of the nucleus and gas production rates is discussed. © 1991.
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页码:350 / 365
页数:16
相关论文
共 36 条
[1]   TRAPPING OF GAS-MIXTURES BY AMORPHOUS WATER ICE [J].
BARNUN, A ;
KLEINFELD, I ;
KOCHAVI, E .
PHYSICAL REVIEW B, 1988, 38 (11) :7749-7754
[2]  
Delsemme A. H., 1952, ANN ASTROPHYS, V15, P1
[3]   PHYSICO-CHEMICAL PHENOMENA IN COMETS .3. CONTINUUM OF COMET BURNHAM (1960 2) [J].
DELSEMME, AH ;
MILLER, DC .
PLANETARY AND SPACE SCIENCE, 1971, 19 (10) :1229-&
[4]  
DHENDECOURT LB, 1989, ASTRON ASTROPHYS, V223, pL5
[5]   THE ORIGIN AND STRUCTURE OF ICY COMETARY NUCLEI [J].
DONN, B .
ICARUS, 1963, 2 (5-6) :396-402
[6]  
ESPINASSE S, 1989, ESA SP302, P185
[7]  
FANALE FP, 1984, ICARUS, V60, P476, DOI 10.1016/0019-1035(84)90157-X
[8]   THE LOSS AND DEPTH OF CO2 ICE IN COMET NUCLEI [J].
FANALE, FP ;
SALVAIL, JR .
ICARUS, 1987, 72 (03) :535-554
[9]   ENTHALPY CHANGES AND HEAT-CAPACITY CHANGES IN TRANSFORMATIONS FROM HIGH-SURFACE-AREA AMORPHOUS ICE TO STABLE HEXAGONAL ICE [J].
GHORMLEY, JA .
JOURNAL OF CHEMICAL PHYSICS, 1968, 48 (01) :503-&
[10]  
Greenberg J. M., 1982, COMETS, P131