A MARTÍNEZ, HOST:
It's easy to dream about space because all you got to do is go outside and look up to see some of what's out there. But the deep ocean - that's not so easy. Because even if you're in the ocean, you can't just look down and see what's in the deep waters.
SUSAN CASEY: Typically, it's defined as the waters below 600 feet. So, as you can imagine, since it goes all the way down to almost 36,000 feet in places, the deep ocean is the vast, vast, vast majority of the ocean.
MARTÍNEZ: Susan Casey has been down there. She's a diver and author of the new book "'The Underworld: Journeys To The Depths Of The Ocean." Casey writes that while most people prefer to go to Paris, Bora Bora or the Serengeti, she's always wanted to go to the ocean's abyss.
CASEY: If you think of the Earth as a biosphere, but 2% of that is everything we see, 98% is ocean, and 95% of that is deep ocean. And I often think of it as, like, living in some mansion filled with rooms full of amazing animals and artworks and treasures. And we've just looked in one or two rooms. I really wanted to look in all of the rooms.
MARTÍNEZ: What's the deepest you've been? I read that you went 16,000 feet deep, right?
CASEY: It was somewhere between 16 and 17, probably closer to 17,000 feet deep. Yes.
MARTÍNEZ: Oh, I'm so sorry - 17,000.
CASEY: Yeah. Listen, there's a lot more below that. But I was very happy to get to that depth because what I was really hoping - when I set out to do this project, it was my greatest hope and dream that I would be able to take readers with me to a really profound depth in the ocean, and that's the literal abyss. And it was a magnificent experience, just real honor to be able to share that with everybody.
MARTÍNEZ: So, OK, aside from what we typically think we know about what's there, what's there?
CASEY: Well, that is a question that's always haunted me. Ever since I started writing about the ocean, I began to notice that there's this parallel universe that pops to the surface every so often, but then it'll disappear again, and we can't really follow it. And there is so much going on down there - a lot of really extraordinary life, a lot of lost history that we are rediscovering. So it's a party down there.
MARTÍNEZ: Well, let me ask you this then. Why don't we seem to care as much about that party as we do about this party above our head - space?
CASEY: I've thought about that a lot, and I still do think about that a lot. And I think it's just out of sight, out of mind. I mean, we can look up in the sky. We can look at the stars through telescopes. But the journey inward is a journey into darkness. It's a journey into a sort of an inner space that makes us less comfortable. It's not a journey of conquest. It's really one of submission.
MARTÍNEZ: In the course of human history, all the shipwrecks, all the stuff that's been thrown in the ocean, I'm wondering just how much manmade stuff is out there.
CASEY: UNESCO has estimated that there are some 3 million undiscovered shipwrecks. Now, not all of those are in the deep ocean. But what's interesting is that when there is a shipwreck in the deep ocean, it's often really well-preserved. But - I don't know if you had a chance to read the book, but there is a chapter about marine archaeology in there, and it focuses on this one shipwreck that's really fascinating that they're going to do a full excavation on at 2,000 feet down. It's called the San Jose, and it's a really unusual shipwreck because they know that it's been preserved perfectly in the seafloor sediment, and it also is filled to the gills with stuff.
MARTÍNEZ: Oh, wow.
CASEY: And its value is estimated at somewhere between 17 billion to 35 billion just in the stuff that's on it. But it's got this absolutely priceless historic value because they know exactly what it was doing, where it went down. And the problem is is that the excavation is going to cost upwards of $50 million, and it - there becomes this sort of battle of, OK, who's going to pay for this and who will own it? But that's the kind of thing that's down there.
MARTÍNEZ: You know, that makes me think of the Titan submersible. How can deep sea exploration coexist with deep sea tourism?
CASEY: Well, any time you go into the deep ocean, you're not really a tourist. I mean, because it's a fairly extreme experience. And the thing about the Titan that is so distressing is that it really is an accident, a tragedy, that didn't have to happen because we're talking about forces that we know what they are and we know how to engineer to withstand them. There's just a tried and true way of getting down there that they disregarded. And unfortunately, the tragedy resulted.
MARTÍNEZ: In the book, you speak to many of the people that are down there often, that have seen things that no one can possibly imagine. Who are some of these people, and what are they most afraid of when it comes to what we don't know about the ocean and the deep ocean?
CASEY: One of the scientists that I write about is Alan Jamieson, who specializes in a - the deepest region of the ocean, which is called the hadal zone after Hades, the god of the underworld. And there are really unusual creatures down there. And they caught this one little crustacean in the Mariana Trench. And when they took it back to sequence it genetically, they discovered that it wasn't fully organic. There was nanoplastics and little micro bits of plastic actually embedded into its organs throughout its body. So it was a sort of a hybrid plastic-organic creature.
MARTÍNEZ: Wow.
CASEY: And they named it Eurythenes plasticus because they caught a lot of these, and they could not find one that did not have plastic incorporated into its body. And so when I asked Alan, OK, so how many other hybrid plastic-organic creatures are there down there? And he just looked at me and said, all of them. So there is a sense that even though it's the most remote and the most difficult to access environment, that this is a small planet and we have an impact even on the farthest reaches of the deep ocean.
MARTÍNEZ: Susan, what have you learned from visiting the depths of the ocean that maybe can tell us something about life here, up at the surface?
CASEY: One of the things that I think is really required for ocean exploration and for dealing with the ocean in general - you need a certain humility that I think would really serve us well to adopt a little bit more in our doings in the terrestrial world. You cannot stand in front of a 70-foot wave, you cannot descend into the abyssal depths of the ocean and think, hey, we're in charge here. We've got it covered. I mean, like, you will very quickly understand that there are forces much greater than we are, and we're not going to conquer them. We're not going to be able to somehow subdue four tons of pressure per square inch. You can only really go there with a real sense of humility. And I think humility, in general, is very undervalued as a superpower.
MARTÍNEZ: Susan Casey wrote "The Underworld: Journeys To The Depths Of The Ocean." Susan, thanks.
CASEY: Thank you.
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