From the outside, Earth doesn't seem to have a lot going on in the hydrogen department… but that doesn't mean it's completely lacking in the most abundant element in the Universe. Bound to oxygen, it sits in plain sight as water. Yet according to a new study, vast amounts of hydrogen could also be locked away in our planet's core, attached to the densely packed alloyed iron that lurks therein. How much? Up to 45 times more than the roughly 150 quintillion kilograms of hydrogen contained in