Bibcode
Ziffer, Julie; Campins, H.; Howell, E. S.; Licandro, J.; Walker, M.; Deshpande, R.; Hargrove, K.
Bibliographical reference
American Astronomical Society, DPS meeting #40, #60.06; Bulletin of the American Astronomical Society, Vol. 40, p.509
Advertised on:
9
2008
Citations
1
Refereed citations
1
Description
We present initial results of a comparative near-infrared (NIR)
spectroscopic study of the Themis and Veritas asteroid families. These
two families are compositionally primitive (mainly Tholen C-types) and
likely formed in the same region of the protoplanetary disk. However,
their disruption ages are at opposite extremes: 2.5 Gy and 8.3 My,
respectively, providing insight into evolutionary processes since their
disruption. Our study was motivated in part by the Nesvorny et al.
(2005) detection of visible color trends between young and old asteroids
families, with these two families at opposite ends of their trend. Our
0.8 to 2.4 micron spectra of four Themis and six Veritas asteroids were
obtained using the SpeX instrument on NASA's Infrared Telescope Facility
(IRTF). We normalized these spectra using solar analog stars; our
reflectance spectra do not exhibit any clear absorption features but
they do show a range of slopes. The four Themis family members (older
surfaces) have "red” (positive) slopes; in contrast, the six
Veritas family members (younger surfaces) have significantly
"flatter” slopes (this result includes objects with similar radii
so it does not appear to be a function of asteroid size). The clustering
of the spectra into two groups with statistically distinct average
slopes is consistent with space weathering being a significant modifier
of the near-infrared spectral shape of primitive asteroids. In other
words, space weathering of primitive asteroids surfaces appears to make
them "redder” in the NIR (this work) and less red in the visible
(Nesvorny et al. 2005).
We gratefully acknowledge support from a Cottrell College Science Award
from Research Corporation, and from National Science Foundation and NASA
grants.