Question: where do asteroids come from?

Hussain Jaffery answered on 9 Nov 2015:

Asteroids formed in the early solar system in the same dust and heat of the Sun and newly forming planets. Before the Sun, planets, and asteroids, there was just gas and dust. All of this pulled together over time, due to gravity, and got so hot it started to burn and smoulder, at the same time causing the spinning of the solar system. As time went on, big lumps started cleaning up the space around them by swallowing the surrounding dust and gas – these became planets.

Asteroids just never got a chance to collect together to form a bigger planet. This is why the two largest asteroid belts are where there is the greatest space between planets. This doesn’t mean that asteroids at totally boring. They have changed over time and we can learn a lot about the history of the solar system from them.