Now we may know. The discovery of rats on Mars - if not an optical illusion - could explain the phenomenon of global terrorism. A force field which continues to strengthen.
Those rats could have hitchhiked on spacecraft from Mars to planet earth. Given the amazing survival intelligence of all rodents, they could have figured out they needed protective coloring.
That generated their identity as terrorists. And since then planet earth has been dominated by these rats.
Warning to space travelers: If you spot a rat on your vehicle or yourself, contact NSA.