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A sulfur cave in Colorado is a site of scientific discovery


Sulfuric acid drips from the ceiling of a cave in Steamboat Springs, Colo., and the air is so full of toxic fumes, people are typically forbidden to go inside. Aaron Scott, the co-host of NPR's science podcast Short Wave, grew up nearby and dreamed of exploring the cave as a kid, thinking it might be full of monsters and treasure. So when he heard about a team of scientists going in, he couldn't pass up the chance to join them. We're going to turn it over to Aaron and Short Wave co-host Emily Kwong to find out why this sulfur cave has become a fascinating site for scientific discovery.

DAVID STEINMANN: There are lots of harmful things in this cave, but if you take the precautions we are and have the gear and the gloves, then you will be safe, I hope.

AARON SCOTT, BYLINE: So in July, I met David Steinmann and three scientists at the cave, which is now fenced off. David's a veteran caver and a research associate with the Denver Museum of Nature and Science, and he's helping the first scientists put on a self-contained breathing apparatus, or SCBA. It's kind of like scuba gear for land.

STEINMANN: Let me turn the air on in the back.


HARRY TUAZON: Oh, there's a rapid noise. OK.

STEINMANN: That's fine.

TUAZON: The same exact one we use in the Navy (laughter).

STEINMANN: Oh, good.

SCOTT: Harry Tuazon is a Ph.D. student at Georgia Tech and a former Navy operations officer, and he brought along two other science students from the Bhamla Lab at Georgia Tech. They're all wearing matching coveralls that they ordered online, and David and Harry are going in first.

STEINMANN: OK. Now you should just be able to breathe comfortably. Yeah, I think you're good to go.

TUAZON: I have my - yep, I have my specimen cups with me, ready to go.

STEINMANN: Here we go.

SCOTT: David and Harry descend and pass through the crack, out of sight but not out of sound.

STEINMANN: Well, we're down in here a little bit, right in the zone where the air's just getting really toxic.

SCOTT: And the reason they're risking life and limb to do this, Emily - the treasure they are questing for is not dragon gold. It is worms - blood-red colored worms that live in writhing, wriggling worm blobs.

EMILY KWONG, BYLINE: There are monsters.

SCOTT: Yes, ever-so-tiny monsters.

STEINMANN: The sulfur cave worms are most interesting because they can live where nothing else in the world would normally be able to live.

SCOTT: And that is the kind of thing that gets scientists excited. Researchers from around the world want to study these sulfur worms in the hopes of finding new antibiotics, medicines or, in the case of Harry and his team, inspiration for robots that could explore other dangerous places.

KWONG: So, Aaron, please tell me you got to go into the sulfur cave, too.

SCOTT: Oh, I did.

KWONG: Heck yeah. OK. We're going to follow you, and I'll just lurk here in the darkness like a cave salamander and listen.

SCOTT: So I strapped the oxygen tank to my back, and I pulled on one of the face masks over my head.

Testing, testing, one, two, three.

STEINMANN: Ready to enter the bowels of the Earth?

SCOTT: I am. Let's go.

And David and I started down the slope that the spring runs down into the cave.

STEINMANN: We're looking into a real jagged crack with lots of sharp edges.

SCOTT: And that crack is what we squeeze through next. It opens up to the first room in the cave. It's maybe five feet tall and about 75 feet long.

STEINMANN: So if you look at the ceiling, there are really amazing crystals.

SCOTT: Can you see any of the snottites?

STEINMANN: Yeah, some of the little drips off the crystals down there are snottites.

KWONG: Excuse me. Excuse me. What are snottites?

SCOTT: (Laughter) Yes, so dripping from the ceiling are these tiny little stalactites that look like they're made out of mucus.

KWONG: No, no.

SCOTT: Thus, snottites. Really, they are actually made up of colonies of bacteria that are metabolizing the hydrogen sulfide that's seeping through the rock into sulfuric acid, so these snottites are literally dripping acid of pH 0 that can burn our clothes and skin. And then below us, the stream itself widens out over the cave floor and disappears into darkness.

Are these bacterial mats?

And the stream bed is covered in these bacterial mats that are white with a yellowish tinge that is just kind of this ghostly sludge, and that is where we find them.

STEINMANN: And if you look, you can see clumps of worms everywhere.

SCOTT: Wow. They really are everywhere. I mean, it's stunning.

STEINMANN: I'm just going to collect a couple worms real quickly.

SCOTT: The worm blobs look like little blood-red sea anemones wriggling in the stream bed, and they live off the bacteria that in turn lives off the sulfur, so it's easy to see why scientists look to places like this sulfur cave to dream up what life might look like on other planets. I mean, between the ghostly sludge covering everything and these writhing worm blobs, it does feel just downright otherworldly, like a place that we humans don't belong.


STEINMANN: OK. That's the sound that means you're running out of air.


STEINMANN: We have to find (inaudible) for you to turn around.

SCOTT: David said that was the sound that I was running out of air, so at that point, we reemerge from the bowels of the Earth, reeking of brimstone.

KWONG: Capital adventure, Aaron.

SCOTT: (Laughter).

KWONG: The people you were with - they sound pretty cool. I mean, this is clearly not David's first time looking for worms in sulfur caves.

SCOTT: No, not at all. He was actually the first person to report seeing them. Back in 2007, there was a group of scientists who wanted to explore sulfur caves, and they sent David in first to document the life there before others could disturb it because finding new species in caves is kind of his thing.

STEINMANN: Over the last 20 years, I've found about a hundred new species. Maybe a couple dozen have been named so far, and there are many more out there. I just sort of like to joke with my friends that if I want to find a new species in a cave, all I have to do is go to a cave I've never been to before. And almost guaranteed, if there's a little moisture, I'll find something.

KWONG: It's really that easy.

SCOTT: It's really that easy. This is one reason I love caves. They're like these little islands of evolution. I mean, they're cut off from other places, and they tend to have this, like, steady temperature and moisture year-round, which means the critters in them often kind of evolve to fit each specific cave.

KWONG: Whoa.

SCOTT: Isn't that amazing? So in the case of an extreme environment like the sulfur caves, the creatures that evolved to flourish there are known as extremophiles. And scientists love these because some of them have evolved novel compounds to survive their hazardous homes, and those compounds could have uses for us, too.

KWONG: Ooh, like what?

SCOTT: Well, researchers have found chemicals in extremophiles that now show up in soaps, biofuels, lactose-free milk - I mean, you name it. And after analyzing these worms, David and several other researchers were able to announce that they were indeed a new species to science, and word spread in extremophile circles.

STEINMANN: I've just been finding more and more researchers over the years have sort of been contacting me to see if I could collect worms for them so that they could study them in new ways, like the antibiotics, the robotic worms, the physiology, the blood, the detoxifying substances.

SCOTT: And then there's Harry and his team from Georgia. They're particularly interested in how the worm blobs move around.

TUAZON: I'm looking into the biology, physics all the way to the robotics. For these worms, we're trying to come up with rules to say, how can they locomote together in an entangled group? We're trying to apply them into the field of, let's say, underwater exploration, cave explorations, maybe space.

KWONG: OK, so robots that can explore other planets, antibiotics, compounds that could oxygenate our blood - it just sounds like a lot of weight placed on the shoulders of these little worms. You know?

SCOTT: Yes. Yes. And to be fair, you know, nothing might come of it. This is all early research, but for David, it's all about the joy and the potential of the search itself.

SHAPIRO: That was Aaron Scott and Emily Kwong from NPR's Short Wave podcast.

(SOUNDBITE OF SLVR SONG, "BACK N FORTH") Transcript provided by NPR, Copyright NPR.