Let me POINT SOMETHING OUT.

If you study the solar system like I have you will realize that there was once a planet where the asteroid belt is located. Mars was a MOON of a planet there.

Implications? The bigger planet blew up, exploded, got hit, or somehow or another became all the rubble you see. Mars was most LIKELY a planet with an atmosphere at the time, green like Earth, and likely had a lot of water then.

When the bigger planet blew up it left rubble. And Mars in the old orbit, actually a bit further away from where the center of gravity would have held it previously.