Results on Collisions Between Asteroids (
Résultats sur les Collisions entre Astéroïdes)
Cover legend: More than
20 asteroid families have been identified in the main asteroid belt,
each the result of collisional break-up of a much larger parent body.
The recently discovered Karin family of asteroids is relatively young
(from a collision that took place about 5 million years ago) and unaffected
by orbital evolution. This provides an opportunity to deduce details of
the internal structure of the parent bodies from observational data.
Numerical simulations of the Karin collision suggest the parent body was
itself internally fragmented and that the collision produced thousands
of fragments, perhaps including near-Earth asteroids and meteorites.
From Michel, P., Benz, W., Richardson, D.C. 2003, Nature
Vol.421, 608-611.
Explications vulgarisées et pour la presse)
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Image taken from the simulation
of the disruption of a 164-km asteroid during a collision with another
asteroid at 5 km/s. Once the body has been fragmented in about 200,000
fragments, their gravitational interactions cause some of them to reaccumulate
and form large aggregates(also called "rubble piles"). This image shows
the result at an instant corresponding to 84 minutes after the impact:
the reaccumulation process is working and the largest fragment in the center
will eventually have a mass about 50% that of the parent body. The final
outcome will be a family of well dispersed small and large fragments formed
by reaccumulation. Some of them will also be accompanied with small satellites.
This simulation has required two months of CPU time on a 4-processor DEC-ALPHA
belonging to the ILGA goup of O.C.A. Other simulations have been performed
on a 8 bi-processor AMD Athlon Beowulf installed by Alineos. Financial support
to P. Michel has also been provided by the Action Thematique Innovante 2001
of INSU.
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