  The cooling histories of individual meteorites can be empirically
reconstructed by using ages from different radioisotopic chronometers with
distinct closure temperatures. For a group of meteorites derived from a single
parent body such data permit the reconstruction of the cooling history and
properties of that body. Particularly suited are H chondrites because precise
radiometric ages over a wide range of closure temperatures are available. A
thermal evolution model for the H chondrite parent body is constructed by using
all H chondrites for which at least three different radiometric ages are
available. Several key parameters determining the thermal evolution of the H
chondrite parent body and the unknown burial depths of the H chondrites are
varied until an optimal fit is obtained. The fit is performed by an 'evolution
algorithm'. Empirical data for eight samples are used for which radiometric
ages are available for at least three different closure temperatures. A set of
parameters for the H chondrite parent body is found that yields excellent
agreement (within error bounds) between the thermal evolution model and
empirical data of six of the examined eight chondrites. The new thermal model
constrains the radius and formation time of the H chondrite parent body
(possibly (6) Hebe), the initial burial depths of the individual H chondrites,
the average surface temperature of the body, the average initial porosity of
the material the body accreted from, and the initial 60Fe content of the H
chondrite parent body.
