Comet 9P/Tempel 1: Interpretation with the Deep Impact Results

Abstract

According to our common understandings, the original surface of a short-period comet nucleus has been lost by sublimation processes during its close approaches to the Sun. Sublimation results in the formation of a dust mantle on the retreated surface and in chemical differentiation of ices over tens or hundreds of meters below the mantle. In the course of NASA's Deep Impact mission, optical and infrared imaging observations of the ejecta plume were conducted by several researchers, but their interpretations of the data came as a big surprise: (1) The nucleus of comet 9P/Tempel 1 is free of a dust mantle, but maintains its pristine crust of submicron-sized carbonaceous grains; (2) Primordial materials are accessible already at a depth of several tens of cm with abundant silicate grains of submicrometer sizes. In this study, we demonstrate that a standard model of cometary nuclei explains well available observational data: (1) A dust mantle with a thickness of ~1-2 m builds up on the surface, where compact aggregates larger than tens of micrometers dominate; (2) Large fluffy aggregates are embedded in chemically differentiated layers as well as in the deepest part of the nucleus with primordial materials. We conclude that the Deep Impact results do not need any peculiar view of a comet nucleus.

11 pages, 1 figure, 1 table. ApJ letters, 673, L199-202

References in corpus (2)

• Two different evolutionary types of comets proved by polarimetric and infrared properties of their dust
• A survey of debris trails from short-period comets

Cited by in corpus (5)

• Comet dust as a mixture of aggregates and solid particles: model consistent with ground-based and space-mission results
• The Morphological, Elastic, and Electric Properties of Dust Aggregates in Comets: A Close Look at COSIMA/Rosetta's Data on Dust in Comet 67P/Churyumov-Gerasimenko
• Light Scattering and Thermal Emission by Primitive Dust Particles in Planetary Systems
• The Dust Mantle of Comet 9P/Tempel 1: Dynamical Constraints on Physical Properties
• Do twin spectral peaks of olivine particles in the thermal infrared diagnose their sizes and porosities?