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On the evolution and activity of cometary nuclei.

D Prialnik1, A Bar-Nun

  • 1Department of Geophysics and Planetary Sciences, Tel-Aviv University.

The Astrophysical Journal
|February 15, 1987
PubMed
Summary

The phase transition of amorphous ice to crystalline ice within cometary nuclei releases significant internal heat. This process, occurring in distinct rounds, drives sublimation and gas release, potentially explaining cometary activity.

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Area of Science:

  • Cometary Science
  • Planetary Science
  • Astrochemistry

Background:

  • Cometary nuclei are primarily composed of amorphous ice.
  • The thermal evolution and phase transitions of cometary ice are crucial for understanding cometary activity.

Purpose of the Study:

  • To numerically simulate the thermal evolution of a cometary nucleus.
  • To investigate the phase transition of amorphous ice to crystalline ice and its implications for cometary activity.

Main Methods:

  • Numerical simulation of a spherical cometary nucleus (2.5 km radius) over 280 revolutions.
  • Modeling the thermal evolution and phase transition front propagation.

Main Results:

  • Amorphous to crystalline ice phase transition occurs in five distinct rounds, releasing internal heat.
  • The transition front advances progressively deeper into the nucleus with each round.
  • Crystallization releases trapped gases, leading to potential explosive events and gas/dust jets.

Conclusions:

  • The amorphous to crystalline ice transition is a major internal heat source for comets.
  • Explosive gas release following crystallization can explain observed cometary activity, including outbursts and jets.
  • This process may be responsible for the activity of new comets and features like volcanic calderas.
Keywords:
NASA Discipline ExobiologyNon-NASA Center

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