# Why do the asteroids orbit the Sun in roughly the same plane as the planets?

The asteroid belt between Mars and Jupiter is an extremely active environment (on an astronomical time scale) where collisions between 10km radius bodies occur every $$10^7$$ years, according to wikipedia. It was likely much more active in the past, before many of the asteroids were ejected due to planetary resonances.

But even after all the collisions throughout the asteroid belt formation until now, the vast majority of currently existing asteroids have low inclinations with respect to the ecliptic. That is, the inclinations of their orbits are roughly aligned with the rest of the planets' orbits around the Sun (credit figure to wikipedia):

Question: Why haven't all the collisions caused the inclinations of the asteroid belt to be more widely distributed?

• There has only been about 300 or so large collisions after the formation and "calming down" of the Solar System. (3 billion / 10^7 = 300) Mar 29 '21 at 20:57
• I am not sure you can assume that the large collision rate was the same in the past, as there were presumably more asteroids back then. Also, close passes would certainly change orbital parameters as well. Mar 29 '21 at 21:07
• According to The Asteroid Belt As A Relic From A Chaotic Early Solar System, "the asteroids' orbits are dynamically excited, with a large spread in eccentricity and inclination. [...] the belt may have been excited by Jupiter's orbital migration. [...] the asteroids may have been excited to their current state if Jupiter's and Saturn's early orbits were chaotic". Mar 30 '21 at 6:36