<P> Approximately one - third of the asteroids in the asteroid belt are members of an asteroid family . These share similar orbital elements, such as semi-major axis, eccentricity, and orbital inclination as well as similar spectral features, all of which indicate a common origin in the breakup of a larger body . Graphical displays of these elements, for members of the asteroid belt, show concentrations indicating the presence of an asteroid family . There are about 20--30 associations that are almost certainly asteroid families . Additional groupings have been found that are less certain . Asteroid families can be confirmed when the members display common spectral features . Smaller associations of asteroids are called groups or clusters . </P> <P> Some of the most prominent families in the asteroid belt (in order of increasing semi-major axes) are the Flora, Eunoma, Koronis, Eos, and Themis families . The Flora family, one of the largest with more than 800 known members, may have formed from a collision less than a billion years ago . The largest asteroid to be a true member of a family (as opposed to an interloper in the case of Ceres with the Gefion family) is 4 Vesta . The Vesta family is believed to have formed as the result of a crater - forming impact on Vesta . Likewise, the HED meteorites may also have originated from Vesta as a result of this collision . </P> <P> Three prominent bands of dust have been found within the asteroid belt . These have similar orbital inclinations as the Eos, Koronis, and Themis asteroid families, and so are possibly associated with those groupings . </P> <P> Skirting the inner edge of the belt (ranging between 1.78 and 2.0 AU, with a mean semi-major axis of 1.9 AU) is the Hungaria family of minor planets . They are named after the main member, 434 Hungaria; the group contains at least 52 named asteroids . The Hungaria group is separated from the main body by the 4: 1 Kirkwood gap and their orbits have a high inclination . Some members belong to the Mars - crossing category of asteroids, and gravitational perturbations by Mars are likely a factor in reducing the total population of this group . </P>

What binds the asteroids to the asteroid belt between mars and jupiter