Two astonishing studies have found a massive body of water could be sloshing around 60 miles below the surface of the Earth.
If this vast sea were to dry up, the conditions necessary for sustaining life on the planet would vanish.
Without the volcanoes produced by this ocean, soil would not be able to thrive and life would be eventually wiped out.
Research from Florida State University and the University of Edinburgh suggests that water exists far deeper within the planet than previously thought.
Scientists believe the water could be equal to 1.5% of the weight of the planet – dwarfing the amount contained in all seven seas.
Lead author of the study Mainak Mookherjee said: “We didn”t think water could be stored by hydrous minerals such as brucite at these depths.
“But now that we know it”s there, we need to figure out how much water could be effectively stored inside it.”
Water is of vital importance in sustaining life on the planet, not least for sustaining volcanic activity beneath the surface.
Speaking to MailOnline, Dr Mookherjee said: “Volcanoes play an important role in generating the Earth”s crust on which we live.
“So if volcanic activity ceases then the crust formation will also stop and the planetary activities will eventually stop.”
It comes after a top scientist told humans to give up fighting climate change – because everyone will be dead in a decade anyway.