Thermal history of comets during residence in the Oort Cloud: Effect of radiogenic heating in combination with the very low thermal conductivity of amorphous ice
Thermal history of comets during residence in the Oort Cloud: Effect of radiogenic heating in combination with the very low thermal conductivity of amorphous ice
复制标题
彗星在奥尔特云中停留期间的热历史：放射性加热与非晶冰极低导热率相结合的影响
DOI：
10.1029/93je01325
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发表时间：
1993
影响因子：
--
通讯作者：
J. Greenberg
中科院分区：
文献类型：
--
作者：
J. Haruyama;Tetsuo Yamamoto;H. Mizutani;J. Greenberg
研究了最初由无定形冰组成的长周期彗星的热历史。结果表明，这样的彗星与一个小的核热导率（κ）经历了失控的内部温度的增加，在奥尔特云居住期间。温度升高是由于放射性核素衰变引起的逐渐加热引发结晶时潜热快速释放的结果。失控温度升高的时间大约是在核形成后的一千万到一亿年，这取决于含有放射性核素的难熔颗粒的比例。由于温度的失控上升，除了表面之下的核素中的大多数非晶冰都转化为结晶冰。这意味着短周期彗星中的冰是从长周期彗星变成短周期彗星的初始时刻开始结晶的。在大卡帕彗星中，温度与小卡帕彗星相比不会上升太多，并且最初的无定形冰被保存下来。导出了核冰结晶的判据。
The thermal history of long-period comets initially composed of amorphous ice is studied. It is shown that such comets with a small nucleus thermal conductivity (kappa) experience a runaway increase in the internal temperature during residence in the Oort cloud. The temperature increase is a result of rapid release of the latent heat at crystallization triggered by gradual heating due to decay of radioactive nuclides. The time of the runaway temperature increase is about ten to a hundred million years after the formation of the nucleus depending on the fraction of refractory grains which contain radioactive nuclides. Most of the amorphous ice in the nuclides except just beneath the surface transforms into crystalline ice due to the runaway temperature increase. This implies that the ice in short-period comets is crystalline from the initial time when the long-period comet becomes a short-period one. In comets with large kappa the temperature does not rise much compared to the small kappa case and the initial amorphous ice is preserved. A criterion for the crystallization of the nucleus ice is derived.