Thermal Evolution of Cometary Nuclei by Radioactive Heating and Possible Formation of Organic Chemicals

Details Thermal Evolution of Cometary Nuclei by Radioactive Heating and Possible Formation of Organic Chemicals Thermal Evolution of Cometary Nuclei by Radioactive Heating and Possible Formation of Organic Chemicals

Feb 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993mnras.260..819y&link_type=abstract

Monthly Notices of the Royal Astronomical Society, vol. 260, 819-825. Article.

Astronomy and Astrophysics

Astronomy

14

Molecular Processes - Comets: General, Comets, Molecular Processes, Halley, Thermal History, Evolution, Comet Nuclei, Radioactivity, Heating, Organic Material, Diffusivity, Radioactive Decay, Models, Ice, Temperature, Melting, Amino Acids, Uranium 238, Uranium 235, Potassium 40, Thorium 232, Periodic Comets, Specific Heat, Conductivity, Chiron, Calculations, Size, Chemistry, Crystallization, Abundance, Condensation, Origin, Formation

Scientific paper

Thermal evolution of large cometary nuclei (radii ≥40 km) due to heating by decay of 238U, 235U, 40K and 232Th is investigated by adopting chemical models based on observations of P/Halley and mineral compositions of C1 chondrites. If the thermal diffusivity of crystallized ice is sufficiently small (κC ≤ 0.0015 cm s-1), the central temperature may reach the melting point of H2O in large nuclei (radii ≃ 200 km), while if the diffusivity is 0.003 or greater, the central temperature will not reach the melting point.
The high temperature attained within cometary nuclei allows molecules such as HCN and NH3 to form various organic compounds such as amino acids through oligomerization, and such compounds might be delivered to the Earth through disintegrations of the large nuclei, which subsequently impact the Earth. The extraterrestrial amino acids found in the K/T boundary layer and in the dust of P/Halley might have been processed in cometary interiors.

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