This thread reminds me of the movieThe Core. Which I enjoyed , and was surprized by. In the Core , we develope a weopon to disrupt the inner Earths Core in order to create Earthquaks on demand . Well things go wrong and we disrupt the inner core to the point where its rotation and a the magnetic field are made inoperable.

I had wondered of Mars when watching this. It is my bad Astronomy fancy that Pheobos was a free roaming asteroid and collided with Mars. Would such a collision destroy Mars's inner core? Sorry for the change of direction