Searching For Life in Volcanoes and Other Extreme Environments | Nat Geo Live

JEFFREY MARLOW: As a scientist, we often go to some of the most extreme places on our planet to collect microbes, bring 'em back, understand what they're doing and how they work. These types of organisms can actually broaden our search for life beyond earth. By knowing what microbes are capable of, we can think about other places where this could be happening. (applause)

A little over a year ago, I found myself camping on the side of an active volcano. I was there as the chief scientist of an expedition that went to examine Vanuatu's Marum crater. And it was unlike any other camping experience I'd ever had. Right outside your tent window, there is constantly a plume of toxic sulfur dioxide. You had to go with a respirator whenever you went outside. It was also smart to wear long sleeves. There are tiny microscopic basaltic needles that would fall down upon you. And when the rain was water, it was acid; it had a pH of about two.

Despite all these hazards, it actually turns out that microbes can survive in these places, and we were there to figure out why. We were there for this; this is the crater. It's about a kilometer across, 500 meters deep. And at the very bottom of it, in this pit of roiling lava, is the world's most active lava lake. We needed to get samples from the very bottom to understand how microbes can survive, so we descended down the cliff, went as close to the edge of the lava lake as we dared.

All around us, lava was spewing, sometimes going over the top of our heads, raining down upon us. It wasn't a great place to be for a very long time. But we were there just long enough to get our critical samples. This is a place where the earth is forming. This is how rocks come to be. They are formed by volcanoes. And everywhere on the surface of the planet, microbes inhabit these rocks. We wanted to see how this started.

We collected samples that were 30 seconds old. We saw them pop up; they were glowing red, they finally cooled off, we picked 'em up. And we got a full time series across days, weeks, months, years, across the island, to figure out when microbes colonized these rocks, what that means in terms of a longer-term succession of microbial community inside these rocks, and how that influences elemental cycles on our planet.

So, volcanoes are enormous, planetary scale, loud, very obvious features. But they actually created these tiny micro-niches that allow for distinct forms of life to exist. And as a geobiologist, my interest is in these interfaces. It's kind of where these planetary scale processes meet on the micro scale. Places like this have been found all over the world. And microbes typically find a way to survive.

There are organisms in the Rio Tinto in southwestern Spain that can breathe metal and create these acidic pools of blood-red water. The minerals that are formed here are actually found on Mars as well. Recently off the coast of Japan, two and a half kilometers deep, below the surface of the ocean, there are methane-producing microbes. This is a whole different class of organism. These are the intra-terrestrials living inside our planet. And the lower temperature limit of life is still completely unknown.

Microbes can survive inside ice, down to negative 20 degrees Celsius, and probably even cooler. When combined, these forces really come together to operate our planet. We're on a microbial world. Let's all just get used to it. These microbes create more than half of the oxygen that we breathe. They mobilize the nutrients that supports any sort of macroscopic life.

And on my quest to understand what the limits of this biology is, I typically focus on the deep sea. We can think of the earth as a battery. In the sub-surface, in those liquids and those gases, those chemicals are said to be reduced. There are a lot of electrons. On the very thin rind of the planet that we operate in, the atmosphere, the surface world, the ocean, that's said to be oxidized. So, where these places meet, this pole and these boundaries of the battery, that's where energy can be harvested.

So, the deep sea is our best opportunity to find new types of metabolism. And there are sort of three canonical categories over the last few decades that have been carved out within this deep sea realm. Black smoker hydrothermal vents are precipitating these metal sulfides, several hundred degrees Celsius. The Lost City hydrothermal system forms from water rock interactions. No magma needed. And this creates an alkaline system that leads to a whole different type of microbes.

And methane seeps. These are places typically where one tectonic plate is subducting beneath another one, and the organic goo that had kinda fallen down on that first plate is being broken down and streaming up through the earth's surface. So, these methane seeps are where I've done most of my work. You can see the methane bubbles coming out. Not as exciting as black smoker vents on TV, perhaps, but more important.

Because they're able to turn that methane into rock, might be the most important thermoregulators on the planet. Methane is an extremely strong greenhouse gas, so by soaking it up into this rock, we can do a lot of good. There are kinda those three main flavors of deep sea chemosynthetic oases that I described, but we're already sensing that there are other flavors as well. Recently in the Mid-Cayman Trough, the deepest and hottest hydrothermal vent ever been discovered.

And off the coast of Antarctica, this carpet of yeti crabs was found around hydrothermal vents. These crabs harvest bacteria on their gills and eat those. It's the microbes, though, that are making the food in the first place from the chemicals in the vents. Nonetheless, most of the deep sea looks like this to us, we have no idea what's going on. (laughter) That's because less than 0.01% of the deep sea has ever been seen by human eyes.

This is the equivalent of Lewis and Clark setting out on their journey, 1804. They leave their fort on the banks of the Missouri River, they walk about a half mile to their canoes. But instead of getting in those canoes, exploring the rest of the continent, seeing bison, seeing Yellowstone, encountering new cultures, seeing the Rockies, seeing a whole other ocean, they spend the rest of their lives walking that half mile and studying that.

So, why do we really care about microbes? What does it mean to expand the realm of metabolic possibility? From a very practical perspective, we can do a lot of good. The project I'm working on right now is taking these deep sea methane-eating metabolism and trying to import it into E. coli through genetic means to turn methane into a bio-fuel. The drugs and biotechnologies of the future will most likely come from the deep sea, or from the massive realm of untapped genetic potential in microbes around the world.

By understanding the vast realm of possibility of microbiology, we're also expanding the realm of potentially habitable worlds beyond our planet. So other calculations that our team had worked on showed that the methane-eating metabolism we see in the deep sea would have actually been energetically possible on Mars in the ancient past when there was water.

But to me, most fundamentally, this search is really getting to the center of what life is all about. What is this crazy, magical process that moves electrons around, and ends up creating these self-sustaining, self-replicating cells, and ultimately leads to civilization and culture? There's so much more to get to, and we're really just starting this journey. I can't wait to see what we find. Thank you. (applause)