**36th DPS Meeting, 8-12 November 2004**

*Session 48 Asteroid Dynamics*

Oral, Friday, November 12, 2004, 3:30-5:00pm, Clark
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## [48.07] Comparing the size-frequency distributions of asteroid families to those produced by SPH/*N*-body impact simulations

*D. D. Durda, W. F. Bottke, D. Nesvorný (SWRI), E. Asphaug (UCSC), D. C. Richardson (Univ. Maryland)*

We investigate the morphology of size-frequency
distributions (SFDs) resulting from impacts into 100-km
diameter parent asteroids, represented by a suite of 160
SPH/*N*-body simulations conducted to study asteroid
satellite formation (Durda et al. 2004; *Icarus* **
170**, 243-257). The spherical basalt projectiles range in
diameter from 10 to 46 km (in equally-spaced mass increments
in logarithmic space, covering six discrete sizes), impact
speeds range from 2.5 to 7 km/s (generally in 1 km/s
increments), and impact angles range from 15^{\circ} to
75^{\circ} (nearly head-on to very oblique) in
15^{\circ} increments. For a given impact speed, the shape
of the SFD tends to be more ``concave" for the smallest
impactors (cratering events) and more ``convex" for the
largest impactors (supercatastrophic disruption). At the
transition point where ``concave" cratering SFDs begin to
transform into more linear power law SFDs, the largest
remnant has a diameter of ~ 20 km. That transition
occurs at smaller impactor sizes for greater impactor speeds
and at greater impactor sizes for larger impactor angles.
Impacts that maximize the number of similar-size largest
remnants (at ~ 20 km) occur at impact speeds of 6-7
km/s with 25-34 km diameter impactors; larger impactors at
higher speeds are required to achieve the same results for
oblique impacts as for smaller impactors at lower speeds
impacting more nearly head-on. The SFDs with the very
shallowest slopes overall derive from impacts at about 4-6
km/s with 25-34 km diameter impactors. These modeled SFD
morphologies match very well the observed SFDs of actual
asteroid families. We find that there are ~ 20 families
produced by catastrophic breakups in the main belt from D >
100 km parent bodies. This suggests that the threshold
specific energy, Q^{*}_{D}, is very close to that predicted by
Benz and Asphaug (1999; *Icarus* **142**, 5-20).

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Bulletin of the American Astronomical Society, **36** #4

© 2004. The American Astronomical Soceity.