Extraterrestrials may spout out toxic gas as a sign of life, researchers suggest

As the search for intelligent extraterrestrial life marches on, researchers have suggested no shortage of possible signs to look for, including carbon monoxide, dust storms and methane, which is commonly emitted from organic means, including humans. But new research suggests that it's possible E.T. isn't producing any of these and is emitting a gas nearly as toxic to humans as carbon monoxide — phosphine.