- Starting in 1800 searches for a "missing planet" between
Mars and Jupiter began turning up a large number of small objects in this region
of the Solar System -- the asteroids.
- The strong gravitational influence of Jupiter prevented a planet
from forming in the region called the ``asteroid belt'' which lies
between the orbits of Mars and Jupiter.
- Jupiter stirred up the planetesimals in the
asteroid belt region.
- Collisions were violent and led to further
fragmentation rather then accretion.
- Tens of thousands of kilometer-sized asteroids circle
the Sun between the orbits of Mars and Jupiter. These chunks
of rock represent the remains of a planet that never formed.
- Some small planetoids formed and differentiated
but were subsequently broken apart in the collisions.
- The battered remnants of these objects populate
the asteroid belt we known today.
- Fragments from asteroid-asteroid collisions are scattered
throughout the inner solar system. Some reach the Earth and
survive the passage through the atmosphere.
- The fragments can consist of rock, or in
some cases, refined iron and nickel.
- In many cases laboratory spectra of these meteorites
directly match the spectra of asteroids observed in
Revised May 7, 2001