Carved by hot gasses from Antarctica’s most active volcano, the Ice Caves of Erebus may hold the secret to finding off-world life.
Towering above the Antarctic research facility McMurdo Station sits the southernmost active volcano in the world, Mount Erebus. Named for the Greek god of the underworld, it’s home to many otherworldly wonders, including one of Earth’s only active lava lakes — imagine the crater of Mount Doom — and miles of icy, crystalline caverns carved out by the volcano’s hot gases slicing through the thick ice sheet that caps the mountain.
“It’s an interface between two extreme substances that doesn’t happen that often on Earth,” says Aaron Curtis, a Ph.D. student from New Mexico Tech who has been studying the caves with supervisor Dr. Phil Kyle for several years.
To Curtis, being in the ice caves is like being on a sci-fi movie set. “It’s misty, and there’s this wild blue filtered light,” caused by Rayleigh scattering of sunlight as it passes through the ice — the same process that makes the sky blue. Some of the caves are expressed on the surface as beautiful ice towers, formed by rapid desublimation (the process of water vapor turning to ice) when the warm volcanic vapors come into contact with frigid Antarctic surface temperatures. The caves are even more stunning on the inside, with millions of fragile, intricate ice crystals hanging from the walls like little glass chandeliers.
We’ve learned a lot about the ice caves since their discovery. “Originally it was thought that some areas of the volcano were warmer than others, and it was conduction that was melting the caves out. But, what we found is that there are actually discrete locations where gas is coming out of the ground, and that’s what’s driving the system.”
Rather than simply hot ground, it’s volcanic gasses themselves that are carving out caverns in the ice. And the presence of those gases is interesting to researchers. “The CO2 probably comes from quite deep in the Earth,” says Curtis. And he’s not kidding. Studies of the amounts of gas and their chemical and isotopic compositions have shown that some of the carbon dioxide is coming from more than 18 km (11 miles) below the surface. That’s deep enough to be beyond the Earth’s crust and into a region of the planet known as the mantle.
There, those gases and the molten rock from which they exsolve, are churning at thousands of degrees and under super-high pressures. Even after the long journey to the surface, where Antarctic temperatures hover around -30°C (-22°F), the gasses have retained some of that primordial heat. The warmest of the caves — aptly named Sauna Cave — has been recorded as hot as 40°C (104°F). According to Curtis, “It’s the only place in Antarctica that you can go and be uncomfortably hot.”
Hot volcanic gases may even be a source of energy for extreme life in the Erebus ice caves. A research team of geobiologists lead by Dr. Hubert Staudigel of the Scripps Institution of Oceanography have discovered some amazing microbial life forms living in the soils of the ice caves. Among those detected is Acidobacteria, a newly devised phylum of bacteria that literally feed off of acidic environments. Since life can thrive in these little biorefuges surrounded by harsh, lifeless conditions, it’s thought that maybe we could find something similar in caves on Mars.
The discovery of life here is one of the reasons that protecting the caves is becoming an important part of studying them. “We’ve had to talk about designating some of the caves totally off limits to anyone,” Curtis says.
But a number of the caves are already restricted to humans for an even more pressing reason: poison gas. The cavers always keep tabs on the gas concentrations to make sure that the air is breathable.
“There’s a whole quarter of the volcano which has caves that we consider not safe for entry,” Curtis says. “So I would like to explore these robotically.”
To that end, Curtis has become an expert at flying quadcopters, small remote-controlled aerial vehicles. Ideally, Curtis’ copter would have a small LiDAR (Light Detection and Ranging) setup on board, which could map the caves in 3D. “It’s basically like in the movie Prometheus,” he says.
Ultimately, ice cave research at Erebus aims at understanding the volcanic degassing that forms the caves. “Understanding it is really important and could save lives,” says Curtis. There’s always more research to be done, but for now, we’re happy with just a glimpse into the unmatched beauty of these frozen labyrinths.
Photos by Nial Peters and Kayla Iacovino