<P> Some of the debris from collisions can form meteoroids that enter the Earth's atmosphere . Of the 50,000 meteorites found on Earth to date, 99.8 percent are believed to have originated in the asteroid belt . </P> <P> In 1918, the Japanese astronomer Kiyotsugu Hirayama noticed that the orbits of some of the asteroids had similar parameters, forming families or groups . </P> <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>

Which solar system object was found on january 1 1801 located between the orbits of mars and jupiter