French version

Simulations of collisions between asteroids have been performed by Patrick Michel (Laboratoire UMR6529 Cassini/CNRS, Observatoire de la Côte d'Azur) and his collaborators from the University of Berne (Switzerland) and Maryland (USA) and have allowed for the first time to obtain some indications on the internal structure of asteroids.  In particular, the results suggest that parent bodies of asteroid families were originally pre-fragmented (filled with fractures and/or voids, and not monolithics) before being each disrupted to form a family. Simulations then show that the formation of a family is produced by the disruption of such a "rubble pile", generating hundreds of thousands of fragments, among which some will eventually beacome near-Earth asteroids and meteorites.

Moreover, the results show that the impact energy needed to produce a given result from a collision highly depends on the internal structure of the target. this is a major information in order to elaborate mitigation strategies stratégies in case of the potential impact of an asteroid with the Earth.

This research is published in the journal Nature of February 6th, 2003 (Michel, P., Benz, W., Richardson, D.C. 2003. Fragmented parent bodies as the origin of asteroid families. Nature 421, 608-611) and the image of a simulation illustrates the cover of the journal.

Michel, P., Benz, W., Richardson, D.C. 2003. Nature Vol. 421, 608-611. (Click here for a pdf copy)

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.

Click here to acces a web page from which videos and pictures of simulations of collisions can be downloaded.

Simulations of collisions already performed by these researchers had already allowed to characterize the role of the fragmentation and of the gravitaional re-accumulation in the formation of asteroid families (Michel, P., Benz, W., Tanga, P., Richardson, D.C. 2001. Collision and gravitational reaccumulation: forming asteroid families and satellites. Science 294, 1696-1700). Click here for an online access of the article and on the line beginning with "Online reprint ...".

This work had also illustrated the cover of the journal Science and of a press release:  communiqué de presse du CNRS (22 novembre 2001)

  Michel, P., Benz, W., Tanga, P., Richardson, D.C. 2001. Science Vol. 294.
Cover Legend: Simulated image of the disruption of a 100-km asteroid. Collisions between large asteroids generate as many as 50,000 kilometer-sized fragments, some of which will eventually reaccumulate to form aggregates. 1696 [Image: P. Michel and P. Tanga]