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Physical Aging in Comets

  • Karen J. Meech
Part of the Astrophysics and Space Science Library book series (ASSL, volume 167)

Abstract

Recent evidence suggests that comets formed at low temperatures (< 25 K) and that, while the interiors have not been considerably altered since formation, the outer layers have undergone substantial modification. Comets exhibit a wide range of physical characteristics, some of which may be attributed to systematic physical differences between comets making their first close approach to the Sun from the Oort cloud (new comets) and those having made many approaches (old comets). These differences may reflect either primordial differences between two populations or the differences may be a manifestation of aging processes. There are many processes that might be responsible for causing aging in comets. These include: (i) radiation damage in the upper layers of the nucleus during the long residences in the Oort cloud, (ii) processing from heating and collisions within the Oort cloud, (iii) loss of highly volatile species from the nucleus on the first passage through the inner Solar System, (iv) buildup of a dusty mantle, which can eventually prohibit further sublimation, and (v) a change in the porosity, and hence the thermal properties of the nucleus. Although (1950) original work on the comet cloud required that new comets fade after their first close passage, past searches for evidence of aging in comets have produced conflicting results, partly due to a lack of systematic data sets. An understanding of the evolutionary processes of comet nuclei that give rise to compositional or physical differences between ‘fresh’ Oort cloud comets and thermally processed periodic comets will improve our knowledge of the possibly primordial comet composition and therefore conditions in the early Solar System. Recent observations suggest that there are distinct differences between the two groups with respect to intrinsic brightness and rate of change of activity as a function of distance.

Keywords

Solar System Light Curve Physical Aging Heliocentric Distance Cometary Nucleus 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media Dordrecht 1991

Authors and Affiliations

  • Karen J. Meech
    • 1
  1. 1.Institute for AstronomyHonoluluUSA

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