00:00 Our planet has five oceans - the Pacific, Atlantic, Indian, Southern, and Arctic.
00:07 Not counting Billy Ocean.
00:09 But it seems there's a sixth one out there too.
00:11 It's just that you can't see it.
00:14 Scientists have found evidence of large amounts of water hidden in the transition zone.
00:19 That's the boundary layer that separates the upper and lower mantle of our planet.
00:24 That boundary goes hundreds of miles deep down below the surface.
00:28 Small diamonds usually form in the mantle, but at depths of up to 155 miles.
00:34 Some of them are very rare.
00:36 They may come from deeper depths.
00:38 That was the case with this fascinating diamond that formed 410 miles below the surface.
00:44 The gem was big enough for scientists to study it and determine what it was made of.
00:49 They were surprised when the composition of this very rare diamond showed that it was
00:53 formed in pretty watery conditions.
00:56 Because of that, such a diamond wouldn't be worth much in jewelry stores, but it was
01:01 priceless in the lab.
01:03 So could this mean there's an ocean under the surface of our planet?
01:07 It would definitely get us closer to the idea Jules Verne had about this whole magical secret
01:13 world inside Earth, including the ocean.
01:17 But that's not exactly the case.
01:19 The water is there, true, but it's not like you can enjoy the view watching waves splashing
01:24 around like on the surface of our planet.
01:27 The water is actually stored within the minerals.
01:30 That's why this area is so wet.
01:33 Let's now move to Africa to keep up with the story, or to be more specific, to a spot called
01:38 the Afar region.
01:40 It's part of Ethiopia and a place where three tectonic plates meet.
01:45 Tectonic plates are large pieces of our planet's crust that slowly move.
01:50 These movements cause earthquakes and produce volcanoes, mountains, deep underwater valleys
01:55 we call trenches, and so on.
01:58 And the Afar Valley is where the Arabian, Somali, and Nubian plates meet.
02:03 Together, they form an intersection in the shape of a Y.
02:06 Why?
02:07 Let me tell you!
02:09 These plates are moving all the time.
02:12 The Somali plate is moving southeast toward the Australian and Indian plates.
02:16 The Arabian plate is moving north, getting closer to the Eurasian plate.
02:21 At some point, it will close the Persian Gulf.
02:24 This movement of plates has created something we call the Great Rift Valley, considering
02:29 there are, you know, all these cool rifts.
02:32 The Aden Ridge to the east, the Red Sea Rift to the west, the Oculus Rift, and the East
02:38 African Rift to the south.
02:40 But the East African Rift is something we want to focus on, because this one could be
02:45 the key to this potential sixth ocean, but this time on the surface.
02:50 A continental rift is a spot where two tectonic plates that form a single continent start
02:56 to separate.
02:58 Here it's the Somali and Nubian plates.
03:00 Together, they're parts that make up Africa.
03:03 If they keep moving in separate directions, this currently continental rift may become
03:08 what we call an oceanic spreading ridge.
03:11 In other words, when the plates are far enough apart from each other, there will be an enormous
03:16 crack between them.
03:18 This way, magma will freely flow up from beneath them.
03:22 It'll be cool and eventually start creating a new ocean floor.
03:26 Africa will be split into two parts, and there will be a new ocean flowing between what will
03:31 turn into two mini continents.
03:34 Nope, it's not time to get your swim trunks and sunscreen yet.
03:38 Even if the Somali and Arabian plates do move far enough to form an oceanic spreading ridge,
03:44 it'll take, eh, millions of years before this happens.
03:48 So I guess it's more interesting to stick to exploring the sixth ocean below the Earth's
03:52 surface for now.
03:54 The idea of subsurface oceans goes beyond the borders of our planet.
03:59 It's possible many moons and planets out there have them too.
04:03 Our home planet is the only one we know about with consistent bodies of liquid water on
04:08 the surface, true.
04:10 In our solar system, we circle around the Sun in something called the habitable zone.
04:15 The temperature and atmospheric pressure within this zone allow water to remain in liquid
04:21 form all the time.
04:23 But a couple of moons in our solar system could also contain significant amounts of
04:27 water under their surface.
04:30 Enceladus, one of Saturn's moons, is the first one.
04:34 Enceladus is a small frozen ball seven times smaller in diameter than our moon, but it's
04:40 the sixth biggest moon of Saturn.
04:42 Nearly a decade ago, a spacecraft found evidence that there was a large ocean under its surface.
04:49 It found and sampled water from the eruptions that resembled geysers.
04:53 A geyser is a rare type of hot spring that erupts and sends jets of steam and water into
04:58 the air.
04:59 You know, like Old Faithful in Yellowstone.
05:02 Well, this water was erupting through fissures in the ice at the south pole of the moon.
05:08 That means there might be a liquid ocean under the thick layers of ice.
05:12 The ocean there is almost nothing like ours.
05:15 The ocean on Earth is relatively shallow, on average 2.2 miles deep, and it covers three
05:21 quarters of our planet's surface.
05:24 It gets colder the closer you come to the sea floor, and is warmer if you stay close
05:28 to the surface because of the Sun's rays.
05:31 The subsurface ocean on Enceladus is at least 18 miles deep.
05:37 It's cooler at the top, because that part is near the ice shell, and warmer at the bottom
05:42 because of the heat coming from the moon's core.
05:45 But both our ocean and the ocean on Enceladus are salty.
05:50 Enceladus is one of the few places in our solar system that has liquid water, which
05:55 makes it an interesting spot to search for signs of life.
05:59 Another one is Europa, one of Jupiter's moons.
06:03 Scientists think similar eruptions of water could be happening there.
06:07 Knowing there are such geysers there tells us these moons have their own source of energy.
06:12 Maybe the energy that makes the water erupt comes from gravity or radiation.
06:18 The same energy could keep a large body of liquid water under the ice.
06:22 It could even support some forms of life.
06:25 There are thousands of planets beyond our solar system that orbit other stars.
06:31 Some are even in the habitable zone.
06:33 Over a quarter of the ones we know about could have liquid water, but the majority of them
06:38 probably have oceans under their surface, like Enceladus and Europa.
06:44 Pluto might be on this list too, since it's possible it hides a liquid ocean under its
06:49 thick frozen shell.
06:51 This subsurface ocean likely formed long after the dwarf planet did, after the heat coming
06:56 from radioactive elements in Pluto's core melted some of its ice.
07:01 There's also something called water worlds.
07:04 Those are moons or planets with global oceans that are more common than we thought.
07:09 I mean, some call Earth a water world too.
07:12 71% of its surface is water, after all.
07:16 And when you look at our home planet from space, you mostly get those blue marble pictures.
07:22 When exploring other planets, especially those outside of our solar system, researchers often
07:28 go with a policy of "follow the water".
07:31 After all, water is the main element we know that's necessary for supporting life.
07:37 And when there's a water world that's close to its parent star, scientists assume it must
07:42 have formed way farther and then moved closer once its orbit shrank.
07:47 The composition of the planet was set when it was in a colder orbit, or, in other words,
07:52 when it made a wider circle around its star.
07:55 We call the process of orbital shrinking a migration, and if water worlds are really
08:01 that common, it can be proof that migration really happens.
08:06 Exoplanets are all those planets that orbit around other stars, not our Sun.
08:11 Some exoplanets may have oceans that are way deeper than any of those in our solar system
08:16 â hundreds or even thousands of miles deep.
08:20 Our Mariana Trench is scary, and it's not even 7 miles deep.
08:24 And those exoplanet oceans are, wow, almost bottomless.
08:29 That's it for today!
08:31 So hey, if you pacified your curiosity, then give the video a like and share it with your
08:35 friends!
08:36 Or if you want more, just click on these videos and stay on the Bright Side!
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