Roughly 85% of Earth's core is iron. Another 10% is nickel. That leaves 5% unaccounted for. Researchers have long hypothesized some combination of light elements comprise the missing portion. Now, lab experiments suggest the most likely light element candidates are hydrogen, silicon and sulfur.

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Roughly 85% of Earth's core is iron. Another 10% is nickel. That leaves 5% unaccounted for. Researchers have long hypothesized some combination of light elements comprise the missing portion. Now, lab experiments suggest the most likely light element candidates are hydrogen, silicon and sulfur.