Most asteroids are in the asteroid belt between Mars and Jupiter.
Asteroids are strongly influenced by the gravity of Jupiter. Asteroids are made of rock, metal, or a combination of the two. Most asteroids are in the asteroid belt between Mars and Jupiter. Eighteenth century astronomers, thinking there might be a small, inconspicuous planet in that gap, started a search for a planet between Mars and Jupiter. For Giuseppe Piazzi, the search paid off on the night of January 1, 1801.