GUY RAZ, host:
There are places on Earth we know less about than we do about outer space, and a small group of committed scientists study these places, places called supercaves. And in 2004, two different teams of explorers climbed into two different caves to discover which was the deepest on Earth.
One of those teams was led by an American researcher named Bill Stone. He was convinced that a cave in Southern Mexico called Cheve was the deepest. The other group went into Krubera, located in the Republic of Georgia. The story is told in a new book called "Blind Descent." And author James Tabor says there's a big difference between an ordinary cave and a supercave.
Mr. JAMES TABOR (Author, "Blind Descent: The Quest To Discover The Deepest Place On Earth"): If you imagine Mount Everest in reverse, that's a really good image to start with. For one thing, they're immensely deep. Krubera, the great cave in Georgia, is 7,000 vertical feet deep. So that...
RAZ: That's about 1.3 miles or something?
Mr. TABOR: A little bit more, actually, and so seven Empire State buildings.
RAZ: Oh my gosh.
Mr. TABOR: But an equally significant dimension is the length. It's almost nine miles from the mouth of the cave down to its terminus. So it would take the explorers a week to get down to the place where exploration was actually occurring. They would spend seven to 10 days exploring there, and then it would take them a week to get out. So these expeditions would spend up to a month underground.
RAZ: The guy exploring Cheve that you write about in the book is an American named Bill Stone. He is a scientist, and he believed at the time that he could find the deepest cave on Earth at Cheve. First of all, tell me about Bill Stone.
Mr. TABOR: He really committed, shortly after graduate school, to finding the deepest cave on Earth. It became his life quest, if you will.
RAZ: Like an obsession.
Mr. TABOR: Yes. He doesn't like that term, but...
(Soundbite of laughter)
Mr. TABOR: But it's not inaccurate, quite frankly. And he has pursued that goal with relentless energy just like any great explorer.
RAZ: So aside from bragging rights, to be able to say I have reached the deepest cave on Earth, I mean, is there also important research that comes out of this?
Mr. TABOR: There is indeed. To tell you, some of the science that's coming out of deep-cave exploration, one are life forms called extremophiles, which are providing new families of antibiotics that are proving effective against many drug-resistant bacteria.
Another thing is that NASA itself is fascinated by the stressors that attack these teams that are underground for a month or so because they replicate, better than any simulation could, the condition that their Mars crews will encounter.
And a third area is we're learning an awful lot about aquifers, you know, those great, subterranean reservoirs...
Mr. TABOR: ...that we all depend on for water, how they're formed, how they share water with each other and how they're polluted, frankly.
RAZ: James Tabor, explain what makes cave exploration so complicated.
Mr. TABOR: There are more than 50 ways that you can die in supercaves.
Mr. TABOR: For example, you can drown. You can inhale poison gas because some caves contain reservoirs of sulfur dioxide and carbon dioxide, things like that. You can be electrocuted. If you're standing in a water chorus no matter how deep in a cave and lightning strikes that up at the surface, it'll travel down, and that has actually happened. That happened to a caver in Krubera. He didn't die, but he was knocked 10 feet across the chamber and suffered severe, third-degree burns.
So there are so many varieties of danger in these supercave explorations. That really creates these immense complications.
RAZ: When Bill Stone and his team went into Cheve in 2004, how long were they inside that cave?
Mr. TABOR: Their expedition was on site for three months. So there were people in the cave, cycling in and out, in and out, because, like a Himalayan expedition, they had people bringing supplies down to multiple camps all the time. So it...
RAZ: And these camps are in, you know, sort of on ledges or relatively safe parts of the cave where you can sleep.
Mr. TABOR: Some are, and some aren't. When you don't have a good, flat surface, a caver sometimes will hang what are called portaledges, which are like the perches that Yosemite climbers hang on a vertical wall (unintelligible).
RAZ: And they're like hammocks.
Mr. TABOR: They're like hammocks, exactly. So you might be very lucky and find a little sandy beach, or you might have to fold yourself up between two great boulders.
RAZ: And in darkness so much of the time.
Mr. TABOR: Absolute eternal darkness. You know, that's such an amazing part of these caves. We see the images of caves, and of course, they're illuminated, and they're beautiful, but the fact is that cavers spend most of their time in the darkness because light is your most precious resource. And when you're not performing a task or traveling, you turn the light off.
RAZ: Stone's team eventually reached the deepest point it could get to. It was not the deepest cave. What happened?
Mr. TABOR: Well, they were able to dive through a sump and a sump is basically a flooded tunnel and that had really frustrated all attempts since 1991.
RAZ: We should explain that. At a certain point in a cave, you are going to reach these sort of inner lakes that you have to either stop, or you put on scuba gear, and you go through them.
Mr. TABOR: And they can be very, very tight, you know, the diameter of your garbage can, or they can be immense, like a New York subway tunnel, for example.
RAZ: And you have to take all your gear with you through that water channel.
Mr. TABOR: That's right.
RAZ: So what happened? I mean, why couldn't they go any deeper?
Mr. TABOR: They reached a point where there were no more flooded passageways. The cave basically just ended. It was as though they had gotten to the summit of that particular mountain. There was nowhere else they could go.
RAZ: The deepest cave was in Georgia, Krubera. That point was found by other explorers, led by a scientist name Alexander Klimchouk. What's the primary difference between Krubera and Cheve, where Bill Stone was exploring?
Mr. TABOR: Well, I described Cheve as being like a giant L.
Mr. TABOR: Krubera is like a giant elevator shaft. It's essentially 7,000 feet deep. It's also a freezing nightmare of a cave. The ambient air temperature in Krubera is 34 degrees Fahrenheit. So in Krubera in particular, death by hypothermia is yet another way that you can expire down there.
RAZ: You talk about something called the rapture. Explain what that is.
Mr. TABOR: Sure. It's been described by people who have suffered an attack as being like an anxiety attack on methamphetamine, on speed. It's just horrible anxiety, panic, fear, beyond anything that you can imagine.
And it turns out that every human body has a unique response to darkness and depth, and at some level, everyone's brain will start to say: I don't belong here. This is a very dangerous place. It's an ancient primordial instinct and it just says: You have to get me out of here, right now.
Luckily, Bill Stone and Alexander Klimchouk and most of their veteran team members did not have any rapture attacks.
RAZ: James Tabor, would you compare these explorers to other great explorers like Neil Armstrong or Don Walsh? Do you think that these cave explorers and what they have done and achieved is that significant?
Mr. TABOR: I really do, when you consider the risks involved, when you consider the technical skills and demands that are required to make these discoveries. The difference, of course, is that they have received nothing like the recognition or understanding that those other, more highly publicized, explorers have.
And so that's one reason I really wanted to write the book. You know, they, people need to know what these fellows did.
RAZ: That's James Tabor. He is the author of "Blind Descent: The Quest To Discover The Deepest Place On Earth."
James Tabor, thank you so much.
Mr. TABOR: Thank you for having me.