Ah. That's what I get for looking over things far too quickly. In that case, this is too expensive, even given its variance in effects. Maybe drop the costs to 5|4 if not 4|3?
Also, I feel it should be a set damage, not a dynamic damage. It can be justified as the spell attracts a target Asteroid with a certain amount of force. Small asteroids will be attracted far more easily and accelerate much faster. And, of course, larger objects shall move more slowly, accelerating downward at a lower rate. But since they are larger, it will compensate for the acceleration and therefore deal equivalent force and, in turn, damage.
