  Meteoroids are pieces of asteroids and comets. They serve as unique probes to
the physical and chemical properties of their parent bodies. We can derive some
of these properties when meteoroids collide with the atmosphere of Earth and
become a meteor or a bolide. Even more information can be obtained when
meteoroids are mechanically strong and slow enough to drop meteorites. Through
physical modeling of bright meteors, we describe their fragmentation in the
atmosphere. We also derive their mechanical strength and the mass distribution
of the fragments, some of which may hit the ground as meteorites. We developed
a semi-automatic program for meteoroid fragmentation modeling using parallel
genetic algorithms. This allowed us to determine the most probable
fragmentation cascade of the meteoroid, and also to specify its initial mass
and velocity. These parameters can be used in turn to derive the heliocentric
orbit of the meteoroid and to place constraints on its likely age as a separate
object. The program offers plausible solutions for the majority of fireballs we
tested, and the quality of the solutions is comparable to that of manual
solutions. The two solutions are not the same in detail, but the derived
quantities, such as the fragment masses of the larger fragments and the proxy
for their mechanical strength, are very similar. With this method, we would
like to describe the mechanical properties and structure of both meteoroids
belonging to major meteor showers and those that cause exceptional fireballs.
