The mass of the entire asteroid belt is only about 0.05% of the Earth's, and the metallic (M-type) ones only 10% of that, so not much effect. Interestingly, Ce

The mass of the entire asteroid belt is only about 0.05% of the Earth's, and the metallic (M-type) ones only 10% of that, so not much effect. Interestingly, Ceres alone is 1/3 of the total mass, and the big four make up half. http://en.wikipedia.org/wiki/Asteroid_belt#Characteristics http://en.wikipedia.org/wiki/Asteroid_belt#Characteristics