DPS 2001 meeting, November 2001
Session 31. Cometary Nuclei and Dynamics
Oral, Chairs: D. Scheeres, C. Lisse, Thursday, November 29, 2001, 2:40-4:20pm, Regency E

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[31.02] Low Albedos Among Candidate Extinct Cometary Nuclei

Y.R. Fernandez, D.C. Jewitt, S.S. Sheppard (UH-IfA)

A cometary nucleus has several possible end-states, some catastrophic, some not. Measuring the albedo distribution of near-Earth objects in comet-like orbits can provide clues to the number of comets that survive their active lifetime intact to become observationally asteroid-like. By ``comet-like orbit,'' we refer to objects with a Tisserand invariant T in the cometary regime, T<3. We present new radiometric albedos for several inactive objects with T<3, including some retrograde objects. We find that most of these objects are as dark or darker than active cometary nuclei, with geometric albedos around 3%, implying that they are candidate extinct comets. Moreover, the current albedo distribution for inactive objects with T<3 shows that an overwhelming majority are on the dark side, far more than would be estimated by the distribution of the T>3 objects. We place an upper limit of 10% to the fraction of near-Earth and unusual asteroids that are extinct comets. (This work is supported by grants from NSF.)


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