CARL AZUZ: Hi, I'm Carl Azuz.
Thank you so much for watching "CNN 10."
We've got something a little different for you today,
a special edition, an in-depth show
because you really can't go anywhere more in-depth
than the Challenger Deep, the deepest
point of the world's deepest trench
in the world's deepest ocean.
We're talking about the Mariana Trench in the Pacific Ocean.
National Geographic describes this
as a scar in the Earth's crust.
It's located about 7 miles beneath the waves.
The trench measures more than 1,500 miles long,
and it's 43 miles wide on average.
So we're talking about a pretty big scar overall.
And the Challenger Deep is near the southern end of it.
It takes a feat of engineering just to get there.
It takes hours of diving to hit bottom,
and it's largely an unexplored frontier.
Even though thousands of people have reached
the top of the world on Mount Everest, fewer than 25
have reached the bottom of it in the Challenger Deep.
New Zealander Rob McCallum is one of them.
On April 8, he became the first person from his country
to go there, and he went along with Tim
McDonald, the first person from Australia to complete the feat.
They sent us this video and everything
else you're about to see.
And I had the opportunity to interview Mr. McCallum
about the experience, not long after he hit rock bottom
and then resurfaced in early 2021.
Let's dive into the special.
ROB MCCALLUM: It's the last unexplored frontier on Earth.
We know very little about this region, what we call
the Haydel zone, which is that area of the ocean below 6,000
meters or 20,000 feet.
CARL AZUZ: You can't just get there in a normal submarine.
What sort of vehicle does it take to withstand
the pressures there?
ROB MCCALLUM: That's a very interesting question because
pressure is entirely relative.
When a spacecraft goes up into space,
they're only experiencing a pressure change
of 1 atmosphere between the inside of the spacecraft
and the outside.
We are dealing with a pressure differential
of around 1,100 atmospheres.
So we dive in a titanium sphere, which is able to withstand
100,000 tons of pressure.
Just on the hatch, through which we get into the submarine,
just the hatch alone has 2,200 tons or around five fully-laden
Boeing 747 pushing down on it.
CARL AZUZ: That's incredible.
I mean, somebody can't go out and buy that.
How does one acquire a vehicle like that?
ROB MCCALLUM: This vehicle was made for the specific purpose.
It was designed and built by Triton Submarines in Florida,
specifically to be able to voyage
down through 7 and 1/2 miles of water column
to get to the bottom.
And that's why it's got kind of an interesting shape.
It looks like a pillow that's on its side,
and that's so that it can drop down through the water
column very, very quickly.
CARL AZUZ: You said very quickly.
How long does it take to get to that depth?
ROB MCCALLUM: It takes around 4 and 1/2 hours
to get to the deepest point of the world's ocean.
We go down through the water at about 6 feet per second.
CARL AZUZ: And coming back?
ROB MCCALLUM: We released ballast weight on the bottom
to spring us off the bottom and head for the surface.
And so, it's about a 3 and 1/2 hour ride home.
CARL AZUZ: What are you seeing when you get to the ocean floor
in the deepest part of it?
ROB MCCALLUM: This is the most fantastic
part of what we're doing.
It's true exploration.
You know, we never know what we're going to see.
Every dive has yielded something fascinating,
often something new to science.
We are seeing creatures for the first time.
We are discovering entire landscapes,
which were previously unknown.
CARL AZUZ: That's still a full day just in travel time.
So how much time does that give you on the ocean's floor?
ROB MCCALLUM: We try to stay down for three
to five hours on the bottom.
You know, it's a big investment of time and energy.
It takes the entire team to get this vehicle prepared
and get it down.
And so we try to use every minute possible on the bottom.
Our submersible has three viewports.
One for each of the occupants, but also
one central one that allows us to see down to the seafloor.
We're also surrounded by very high
definition cameras that are all linked to a touchscreen
in front of us.
And we can look in any direction outside.
And that's important because we don't
really know where we're going.
We're almost always the very first humans
that have ever been there.
And so although we have a three-dimensional map
that we've made the day before, we need a very good view
outside to see what's coming.
You know, for humans, we don't really
fear what we can't sense.
And so when you're in an airliner
and you're looking out, you don't naturally
think of the wind going past at 500 miles an hour,
and it's minus 50 out there, and there's
not enough air to breathe.
If I can see a town or I can see a track.
And the same in the sub.
There's no sensation of movement.
There's no sensation of sound.
You can't hear or feel anything from outside.
It's just a very peaceful, relaxing
cruise into the unknown.
I think that we know so little about the ocean
that we barely understand what questions
to ask, let alone have the ability
to understand the answers.
My role and the role of the team that I work with
is to simply open the door.
This is the first vehicle in all of human history
that has the ability to reach the deep ocean in any ocean,
at any depth, at any time.
It's akin to the Wright brothers with the first flying machine.
This is just the first baby steps.
CARL AZUZ: I know the technology might
be a way away from creating a ocean exploration station that
can withstand depths like that.
But we have reported on-- there is
more funding and investment in underwater exploration
stations.
I mean, how important would you feel
those would be as contrasted with, let's say,
the International Space Station.
ROB MCCALLUM: Both are important, don't get me wrong.
I'm not taking a shot at space travel.
But you know, space is a vast void, a vacuum that, so
far, has proved to be lifeless.
The ocean is nothing like that.
The ocean is full of life.
You know, right from the surface,
all the way down to the very, very bottom.
I think before we leave home and start exploring the heavens,
we should, at least, explore our own backyard more thoroughly.
I think that many of the answers to our collective future
are going to be found in the ocean, and some
of those in the deep ocean.
The answers to how we're going to handle all the carbon
in the atmosphere, the answers to the dynamics of our ocean
and how we can arrest the decline of the ocean,
but also the things that we might discover in terms
of valuable compounds for medicines and that sort
of thing.
CARL AZUZ: So why do you think there's so much interest
in space exploration when we could be exploring
what we have right here?
ROB MCCALLUM: I think it's as simple
as when we gaze up at the heavens,
we are we have a sense of wonder.
What's out there?
What can we find?
We always look skyward because we're terrestrial mammals.
We look up to the heavens.
When we look into the water, we don't really see that much.
We see an opaque, plain platform that we can pull fish out
of, maybe go for a swimming, but we
don't actually go too far down.
You know, my dive was about 36,000 feet.
Most humans never get below about 300 feet.
So there's a long way to go yet.
CARL AZUZ: So it appears we've barely scratched the surface,
and there's still so many questions in limbo,
except how low you can go because we know from those
who've plumbed the depths and helped
us both deepen our sea of knowledge
and reach new heights of understanding.
Today's show takes us to Plano, as
in Plano, Texas, where we heard from Plano
West Senior High School.
If you'd like a shout out to your school,
and we know you do, please subscribe and comment
at youtube.com/cnn10.
I don't personally choose the schools we mention.
They're emailed to me daily by someone who
only looks on our YouTube site.
I'm Carl Azuz for CNN.