Observational constraints on surface characteristics of comet nuclei

    Authors

    H. Campins;Y. Fernandez

    Comments

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    Abbreviated Journal Title

    Earth Moon Planets

    Keywords

    comets; nuclei; surfaces; KUIPER-BELT OBJECTS; SHORT-PERIOD COMETS; THERMAL INFRARED; SPECTROPHOTOMETRY; JUPITER-FAMILY COMETS; NEAR-EARTH ASTEROIDS; INNER; COMA; ALBEDO; Astronomy & Astrophysics; Geosciences, Multidisciplinary

    Abstract

    Direct observations of the nuclear surfaces of comets have been difficult; however a growing number of studies are overcoming observational challenges and yielding new information on cometary surfaces. In this review, we focus on recent determinations of the albedos, reflectances, and thermal inertias of comet nuclei. There is not much diversity in the geometric albedo of the comet nuclei observed so far (a range of 0.025 to 0.06). There is a greater diversity of albedos among the Centaurs, and the sample of properly observed TNOs (2) is still too small. Based on their albedos and Tisserand invariants, Fernandez et al. (2001) estimate that about 5% of the near-Earth asteroids have a cometary origin, and place an upper limit of 10%. The agreement between this estimate and two other independent methods provide the strongest constraint to date on the fraction of objects that comets contribute to the population of near-Earth asteroids. There is a diversity of visible colors among comets, extinct comet candidates, Centaurs and TNOs. Comet nuclei are clearly not as red as the reddest Centaurs and TNOs. What Jewitt (2002) calls ultra-red matter seems to be absent from the surfaces of comet nuclei. Rotationally resolved observations of both colors and albedos are needed to disentangle the effects of rotational variability from other intrinsic qualities. New constraints on thermal inertia of comets are consistent with previous independent estimates. The thermal inertia estimates for Centaurs 2060 Chiron and 8405 Asbolus are significantly lower than predicted by thermal models, and also lower than the few upper limits or constraints known for active, ordinary nuclei.

    Journal Title

    Earth Moon and Planets

    Volume

    89

    Issue/Number

    1-4

    Publication Date

    1-1-2002

    Document Type

    Article; Proceedings Paper

    Language

    English

    First Page

    117

    Last Page

    134

    WOS Identifier

    WOS:000179660300007

    ISSN

    0167-9295

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