Since 1994 it has been suggested that Jupiter has helped to protect the Earth from impacts. This theory is now being questioned. Early modelling suggests it may not be the case, but there's more to do.
But like many 'early' models - it looked at very specific cases - Centaurs only.... it is, however an interesting theory - we do know that Jupiter has the power to deflect in just as it has the power to deflect out. It's also possible that in clearing the Kirkwood gaps that it cast many a main belt asteroid on an NEO path!
