Serpentinized rocks formed near fast-spreading tectonic plates under Earth's seafloor could be a large and previously overlooked source of free hydrogen gas, a new study finds. The finding could have far-ranging implications since scientists believe hydrogen might be the fuel source responsible for triggering life on Earth. And, if it were found in large enough quantities, hydrogen could be used as a clean-burning substitute for fossil fuels today.The finding could have far-ranging implications since scientists believe H2 might be the fuel source responsible for triggering life on Earth. And, if it were found in large enough quantities, some experts speculate that it could be used as a clean-burning substitute for fossil fuels today because it gives off high amounts of energy when burned but emits only water, not carbon.Recent discoveries of free hydrogen gas, which was once thought to be very rare, have been made near slow-spreading tectonic plates deep beneath Earth's continents and under the sea.