00:00Our planet is home to five oceans, the Pacific, the Atlantic, the Indian, the South and the Arctic.
00:06Not to mention the Balearic Islands, of course.
00:09However, it seems that a sixth ocean may exist, although it is invisible.
00:14Scientists have discovered traces of vast amounts of water hidden in the transition zone,
00:19a layer that separates the upper mantle from the lower mantle of our planet.
00:23This limit extends from 410 to 660 km, under the Earth's surface.
00:28Natural diamonds are generally formed in the mantle at depths of up to 250 km.
00:34Some of them, very rare, can come from much deeper depths.
00:39This is the case of this fascinating diamond, which formed at 660 km from the surface.
00:44The gem, measuring 1.50 F, was large enough for scientists to study it and determine its composition.
00:52They were surprised to find that this extremely rare diamond was formed in rather humid conditions.
00:58As a result, such a diamond would have little jewelry value, but its importance in the laboratory would be inestimable.
01:06So, does this mean that there is an ocean under the surface of our planet?
01:11This discovery certainly brings us closer to the idea that Jules Verne made of this supernatural and secret world in the center of the Earth,
01:18starting with its hidden ocean.
01:21But this is not quite the case.
01:23The water is well present, but it is not a well-visible extension with waves clapping here and there like on the surface of our planet.
01:31In reality, the water is stored inside the minerals, which makes this area so humid.
01:37Let us now head to Africa to continue our story,
01:41or, to be more precise, to a region called Afar, located in Ethiopia.
01:47This is where three tectonic plates meet.
01:50The tectonic plates are large sections of the Earth's crust that move slowly.
01:56These movements cause earthquakes, give birth to volcanoes, mountains, and deep underwater valleys that we call pits.
02:06In the Afar region, the Arabic, Somali and Nubian plates meet to form an intersection in the shape of an I.
02:13Why? Let me explain.
02:16These plates are constantly moving.
02:18The Somali plate moves to the southeast, towards the Australian and Indian plates.
02:23The Arabic plate moves to the north, approaching the Eurasian plate, and will eventually close the Persian Gulf.
02:30This movement of the plates created the Great Rift Valley, marked by geological fractures.
02:35The East Adenian Dorsal, the Red Sea Rift to the west, the South East African Rift, and why not the Occulus Rift?
02:44It is on the East African Rift that we must focus, because it could well hold the key to this sixth potential ocean, but this time on the surface.
02:53A continental fracture is a region where two tectonic plates belonging to the same continent begin to separate.
02:59In this case, these are the Somali and Nubian plates, which make up part of Africa.
03:05If they continue to move in opposite directions, this continental fracture could become what we call an oceanic dorsal.
03:13In other words, when the plates move away enough from each other, a vast crack forms between them.
03:20Thus, the magma will be able to escape freely from the base of these plates, cool down, and begin to form a new oceanic bottom.
03:27Africa will then split in two, and a new ocean will spread between these future mini-continents.
03:33Do not take out your swimsuits and your solar screen yet.
03:36Even if the Somali and Nubian plates move enough to form an oceanic dorsal, it will probably take millions of years to happen.
03:45It is therefore more just to continue exploring this sixth ocean buried under the Earth's surface for the moment.
03:51The idea of an underground ocean goes beyond the borders of our good old Earth.
03:55It is possible that many moons and planets also have one.
04:00To our knowledge, our planet is the only one to present constant liquid water expanses on the surface.
04:06In our solar system, we revolve around the sun in a region called the habitable zone.
04:12The temperature and atmospheric pressure in this zone allow water to remain liquid.
04:18However, some moons of our solar system could also house significant amounts of water under their surface.
04:25Encelade, one of Saturn's moons, is a notable example.
04:29Encelade is a small ice sphere, about seven times smaller in diameter than our moon, or 550 km, but it is Saturn's sixth largest satellite.
04:40About a decade ago, in 2014, a space probe discovered evidence of the presence of a vast ocean under its surface.
04:47It detected and analyzed water ejected during eruptions similar to those of Geyser.
04:53A geyser is a rare hot spring that projects steam and water jets into the air, like the famous Old Faithful of Yellowstone.
05:01On Encelade, this water spills through cracks in the ice of its south pole, suggesting the existence of a liquid ocean below.
05:09This underground ocean is very different from ours.
05:12Earth's oceans are relatively shallow, with an average depth of 3,500 meters, and they cover three quarters of our planet's surface.
05:21The temperature of our oceans varies.
05:24It is colder at the bottom and warmer near the surface due to the sun's rays.
05:29However, the ocean under Encelade's surface is at least 30 km deep.
05:35It is colder at the surface, near this icy crust, and warmer at the bottom, due to the heat coming from the moon's core.
05:43But just like our oceans, Encelade's ocean is salty.
05:47Encelade is one of the rare places in our solar system where we find liquid water, which makes it a major point of interest in the search for signs of life.
05:55Another example is that of Europe, a Jupiter moon.
05:58Scientists think that similar water eruptions could occur in Europe.
06:03The presence of such a geyser indicates that these moons have their own source of energy.
06:08And this energy, which could come from gravity or radiation, would be able to maintain a wide range of water in a liquid state under the ice, and perhaps even feed certain forms of life.
06:21There are thousands of planets beyond our solar system that orbit around other stars.
06:27Some of them are even in a habitable zone.
06:30More than a quarter of these planets could be sheltered from liquid water.
06:34However, most of them probably have underground oceans, similar to those in Encelade and Europe.
06:41Pluto could also be added to this list, because it is possible that it hides a liquid ocean under its thick and icy crust.
06:49This underground ocean probably formed long after the planet Nen, when the heat from the radioactive elements in Pluto's core melted part of its ice.
06:59There are also ocean planets, moons, or planets covered with global oceans.
07:05And they are more widespread than we thought.
07:08Some even call the Earth an oceanic world, because 71% of its surface is covered with water.
07:15Seen from space, our planet essentially appears like a majestic blue ball.
07:20When they explore other planets, especially those outside our solar system, researchers often adopt an approach consisting of following the water.
07:28Indeed, water is the element necessary to support life as we know it.
07:32As for the planets-oceans close to their star-like relatives,
07:35scientists assume that they formed much further away before getting closer when their orbit shrank.
07:42The composition of these planets was determined when they were on a colder and farther orbit,
07:48or in other words, when they described a wider circle around their star.
07:54This process of orbital shrinkage is what we call a migration.
07:59If the ocean-planets are really so widespread, this could be proof that planetary migration is a real phenomenon.
08:07Exoplanets are planets that gravitate around stars other than our sun.
08:12Some of these exoplanets could be sheltered by oceans much deeper than those of our solar system, reaching hundreds or even thousands of kilometers deep.
08:21To put this into perspective, the Marian Foss, which is already impressive and formidable,
08:27with nearly 11 kilometers deep, seems comparatively shallow.
08:31The oceans of these exoplanets seem, at least, unfathomable.
