[meteorite-list] A Recent Asteroid Crackup

From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:06:13 2004
Message-ID: <3DC5A3DF.BAC7BC75_at_lehrer.uni-karlsruhe.de>

A Recent Asteroid Crackup (Govert Schilling)

Planetary scientists have identified fragments from a solar-system
smashup that happened only 5.8 million years ago - just yesterday,
cosmically speaking. That appears to be when a main-belt asteroid
about 25 kilometers across was shattered by a much smaller body
striking it at 5 km per second. So far there are 39 known fragments
from this crackup; the largest, 832 Karin, is 19 km wide.

David Nesvorný (Southwest Research Institute, Boulder, Colorado)
and three colleagues found the cluster by carefully sifting through
tens of thousands of minor-planet orbits to isolate those with similar
semimajor axes, eccentricities, and inclinations. Then, by extrapolating
the slowly changing orientations of 13 of these orbits backward in time,
the team found that they were all aligned with each other 5.8 ± 0.2
million years ago - presumably the fateful date when their parent body
was smashed to pieces.

The Karin cluster is part of the much larger Koronis family. How-
ever, in this and other older family associations, the orbits have been
changed too much by subsequent collisions, gravitational disturbances,
and radiation pressure to be traced back to a common origin. "This
new cluster will no doubt be the focus of attention for the asteroid
community for some time," writes Derek C. Richardson (University
of Maryland) in the June 13th issue of Nature.

(Sky and Telescope, Nov. 2002, p. 20)
Received on Sun 03 Nov 2002 05:31:59 PM PST