One potential issue could be some sort of alien defensive system that neutralizes nuclear bombs, although if the aliens can deactivate nukes, they should have no problems deactivating those Xcom commandos boarding their ship.

FORBES: Why Don't We Nuke the Aliens in Xcom?

That's an alien concept for most people that come out of our education system.

BBC: Networking: Does everybody need to schmooze to get on?

But just why ancient people created the Nazca Lines has been an enduring mystery: Some archaeologists have suggested it was an alien landing strip, a primitive sun calendar, or an irrigation system.

MSN: Peru's mysterious Nazca Lines form a labyrinth, says study