Bibcode
Ziffer, Julie; Campins, Humberto; Licandro, J.; Walker, Matthew E.; Fernandez, Yanga; Clark, Beth Ellen; Mothe-Diniz, Thais; Howell, Ellen; Deshpande, Rohit
Referencia bibliográfica
Icarus, Volume 213, Issue 2, p. 538-546.
Fecha de publicación:
6
2011
Revista
Número de citas
30
Número de citas referidas
30
Descripción
We compare 13 near-infrared (0.8-2.4 μm) spectra of two low
albedo C complex outer-belt asteroid families: Themis and Veritas. The
disruption ages of these two families lie at opposite extremes: 2.5
± 1.0 Gyr and 8.7 ± 1.7 Myr, respectively. We found
striking differences between the two families, which show a range of
spectral shapes and slopes. The seven Themis family members (older
surfaces) have "red" (positive) slopes in the 1.6-2.4 μm
region; in contrast, the six Veritas members (younger surfaces) have
significantly "flatter" slopes at these same wavelengths. Moreover, the
two families are characterized by different concavity at shorter
(1.0-1.5 μm) wavelengths with the Themis group being
consistently flat or concave up (smile) and the Veritas group being
consistently concave down (frown). Each family contains a broad range of
diameters, suggesting our results are not due to comparisons of
asteroids of different sizes. The statistically significant clustering
of the two spectral groups could be explained by one of the following
three possibilities or a combination of them: (1) space weathering
effects, (2) differences in original composition, or (3) differences in
thermal history perhaps as a result of the difference in parent body
sizes. As a result of our analyses, we propose a new method to quantify
broad and shallow structures in the spectra of primitive asteroids. We
found reasonable matches between the observed asteroids and individual
carbonaceous chondrite meteorites. Because these meteoritic fits
represent fresh surfaces, space weathering is neither necessary nor
ruled out as an explanation of spectral differences between families.
The six Veritas family near-infrared (NIR) spectra represent the first
NIR analysis of this family, thus significantly increasing our
understanding of this family over these wavelengths.
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