A true (genetic) asteroid family is the fragments of a disrupted parent body which follow similar orbits around the Sun (dynamical association). The Ceres asteroid family is a dynamical association of 7 asteroids at approximately 2.8 AU from the Sun. Asteroid collisional evolution models  suggest that 1 Ceres is an intact object and is unlikely to have suffered impacts capable of producing the other family members. Based on the taxonomic mix of these family members, it has been suggested that Ceres may be an interloper in its own family, or that this may not be a true (genetic) family. However, the most recent work shows that a genetic relationship probably exists between 3 family members (39 Laetitia, 264 Libussa, and 446 Aeternitas). Prior to the present study, asteroid family work had been limited to dynamical or taxonomic evaluations of family memberships. Dynamical studies are required to identify statistically significant clusters of asteroids. Taxonomic studies are suggestive and often point out intriguing puzzles to work on. However, only a careful analysis of the family member geology and mineralogy allows a genetic family membership to be established and interlopers to be identified. Using the compositions of the genetic family members it is possible to determine the degree of differentiation and stratigraphy of the parent body of the family. This, in turn, allows us to accurately determine the size, thermal history and original composition of the parent body. Recently, spectrophotometric data were obtained for the remaining members (374 Burgundia, 403 Cyane, and 441 Bathilde) of the Ceres family which permits the genetic study of this family. This is the first detailed compositional study of an asteroid family. ACKNOWLEDGEMENTS: Various portions of this work were supported by NSF Solar System Astronomy grant AST-9012180 and by NASA Planetary Geology and Geophysics grant NAGW-642. M.J. Gaffey and M.S. Kelley are Visiting Astronomers at the IRTF which is operated by the Univ. of Hawai'i under contract to the National Aeronautics and Space Administration.
AAS/Division for Planetary Sciences Meeting Abstracts #28
- Pub Date:
- September 1996