Discussion for : An Asteroid Breakup 160 My Ago as the Probable Source of the K - T Impactor

To identify members of the BAF, we applied the Hierarchical Clustering Method (HCM) to search for asteroids near (298) Baptistina in proper element space (e.g., Bendjoya and Zappalà 2002, and references therein). Proper orbital elements, being more constant over time than instantaneous orbital elements (Knežević et al. 2002), provide a dynamical criterion of whether or not a group of bodies has a common ancestor. The orbital parameters of (298) Baptistina are proper semimajor axis aP = 2.264 AU, proper eccentricity eP = 0.15, and proper inclination iP = 5.7◦ (Knežević and Milani 2003).