# Abstract:

## "Velocity Distributions among Colliding Asteroids"

### W. F. Bottke, Jr. M. C. Nolan, R. Greenberg, and R. A. Kolvoord

### (1994) Icarus 107, 255-268.

The probability distribution for impact velocities between two given
asteroids is wide,
non-gaussian, and often contains spikes according to our new method of
analysis in which
each possible orbital geometry for collision is weighted according to its probability. An
average value would only give a good representation if the distribution were smooth and
narrow. Therefore, the complete velocity distribution we obtain for various asteroid
populations differs significantly from published histograms of average velocities. For all
pairs among the 682 asteroids in the main-belt with D > 50 km, we find that our
computed velocity distribution is much wider than previously computed histograms of
average velocities. In this case, the most probable impact velocity is ~ 4.4 km/s, comparedwith the mean impact velocity of 5.3 km/s. For cases of a single asteroid
(e.g. Gaspra or Ida) relative to an impacting population, the distribution we find
yields lower velocities than previously reported by others. The width of these
velocity distributions implies that mean impact velocities must be used with
caution when calculating asteroid collisional lifetimes or crater-size distributions.
Since the most probable impact velocities are lower than the mean, disruption events
may occur less frequently than previously estimated. However, this disruption rate
may be balanced somewhat by an apparent increase in the frequency of high
velocity impacts between asteroids. These results have implications for
issues such as asteroidal disruption rates, the amount/type of impact ejecta
available for meteoritical delivery to the Earth, and the geology and
evolution of specific asteroids like Gaspra.