Antarctica has yielded plenty of Mars rocks, bits of Mars that were blasted off one planet by a collision to eventually land on earth. I think that dropping millions/billions more comets onto Mars might come back to haunt us.
That would depend on the angle of attack and impact speed, wouldn't it?
At that rate we should just strap boosters to Mars and bring it to Earth's orbit
ENOBUDGET Unable to allocate sufficient funding
Request issued for additional platinum-iridium rich asteroids to be delivered to Earth orbit.
ENETUNREACH: The Chinorussese Solar Federation is blockading platinum rich asteroids until they get back war criminal and musician Vladimir the handyman, accused of using a wrench to knock a satellite of out orbit back onto Earth