There are at least two reasons to expect that this is the case. The principal driving force behind meteorite studies is the fact that small bodies such as asteroids and comets are most likely to preserve evidence of events that took place in the early solar system. For further discussion of the sources of meteorites and the processes by which they are brought to Earth, see meteor and meteoroid: Reservoirs of meteoroids in space and Directing meteoroids to Earth. Although evidence from studies of meteors suggests that a small fraction of the cometary material that enters Earth’s atmosphere in discrete chunks possesses sufficient strength to survive to reach the surface, it is not generally believed that any of this material exists in meteorite collections. On the other hand, there is good reason to believe that a significant fraction of the micrometeorites found drifting down through Earth’s upper atmosphere come from comets.
Fewer than 1 percent of meteorites are thought to come from the Moon or Mars. Not all meteoroids need to have formed in this region, however, as there are a number of processes that can cause their orbits to migrate over long time periods. ) It is in this region that strong gravitational perturbations by the planets, especially Jupiter, can put meteoroids into Earth-crossing orbits. (One astronomical unit is the average distance from Earth to the Sun-about 150 million km. Laboratory, astronomical, and theoretical studies show that most discrete meteorites found on Earth are fragments of asteroids that orbit in the inner portion of the main asteroid belt, between about 2.1 and 3.3 astronomical units (AU) from the Sun. Overview of meteorites and their impact on the earth See all videos for this article
METEORITE IDENTIFICATION PICTURES HOW TO
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