The asteroid belt slit the inner planets from the outer planets. Asteroids have known atmosphere. Asteroids can cause craters to accrue. The moons craters where formed by asteroids hitting the planets. Depending on the impact of the asteroid it can cause craters up to ten miles wide.
Asteroids can cause meteors to accrue.
The way they form is that they get knocked out of their orbit and enter Earth's atmosphere and burn up. On June 30,1908, a small asteroid 330 feet in diameter hit a empty region in Siberia. It destroyed half a million acres. The asteriod belt is. Asteriods are rocky, meatial materals.