The ozone hole is the problem that never seems to ever go away. And now it turns out we have a second one to worry about over the Arctic.
Remember chlorofluorocarbons, aka CFCs? The big, bad ozone-depleting pollutant 1) sticks around for tens of thousands of years and 2) is almost entirely man-made. That means if extraterrestrial life are anything like us, according to astrophysicists at Harvard, CFCs could be a key to finding aliens.