In 1977, a submersible named Alvin descended into the Galápagos Rift and stumbled onto something that rewrote biology textbooks. Giant tubeworms—eight feet tall, no mouth, no gut—swaying in pitch-black water heated to 750°F. They were thriving.
The scientists onboard weren’t looking for life. They were mapping the seafloor. But there it was: entire ecosystems powered not by sunlight but by chemicals belching from Earth’s crust. Sulfur-oxidizing bacteria formed the base of the food chain, converting hydrogen sulfide into energy. The tubeworms? They housed these bacteria in specialized organs, essentially farming their own fuel source. It was like discovering photosynthesis had an evil twin that worked in the dark.
Here’s the thing about hydrothermal vents—they’re basically underwater volcanoes on a slow drip.
Why Europa’s Ice-Covered Ocean Might Be Throwing Underwater Ragers Right Now
Jupiter’s moon Europa has a surface made of ice thicker than Mount Everest is tall. Beneath that? An ocean containing twice as much water as all of Earth’s oceans combined. And at the bottom of that ocean, planetary scientists are almost certain there are hydrothermal vents. The tidal forces from Jupiter’s gravity squeeze Europa like a stress ball, generating heat through friction. That heat has to go somewhere.
In 2019, NASA’s Galileo mission data revealed plumes of water vapor erupting from Europa’s surface—geysers shooting 120 miles into space. The chemical signature? Salt. Silicates. Hydrogen. Exactly what you’d expect from hydrothermal activity. The same year, researchers at the Southwest Research Institute calculated that Europa’s seafloor vents could produce ten times more hydrogen than Earth’s vents. Hydrogen is the molecular equivalent of rocket fuel for microbes.
Turns out we’ve already found the ingredients for life’s chemistry set scattered across the solar system.
Enceladus, Saturn’s tiny moon barely 300 miles wide, is even more bonkers. In 2005, the Cassini spacecraft photographed jets of water erupting from cracks in its south polar region. Not just water—organic molecules, including methane and molecular hydrogen. In 2018, scientists detected complex carbon compounds in those plumes. The kind produced by hydrothermal reactions between hot water and rock. The kind that, on Earth, microbes devour like candy.
The Extremophiles That Laugh at Your Fragile Definition of Habitable
Wait—maybe we need to talk about what “extreme” actually means. On Earth, we’ve found life in the Mariana Trench at 36,000 feet below sea level, where pressure would crush a human skull like a grape. We’ve found it in Chile’s Atacama Desert, where it hasn’t rained in 400 years. We’ve found thermophiles—heat-loving bacteria—in Yellowstone’s Grand Prismatic Spring, thriving at 189°F. The record holder, Geogemma barossii, grows best at 250°F and can survive up to 266°F.
These organisms aren’t just surviving. They’re thriving. Reproducing. Evolving.
In 2013, researchers drilling into the Chicxulub impact crater—the one that killed the dinosaurs 66 million years ago—found microbes living in rock nearly a mile underground. The temperature there? Around 140°F. These bacteria were eating sulfur and breathing iron oxide. They’d been down there, isolated from the surface world, for milenia. Just doing their thing in the dark.
The point is: life doesn’t need what we thought it needed. It doesn’t require moderate temperatures, breathable air, or a sun. It needs liquid water, chemical energy, and time. That’s the short list.
When Spacecraft Start Sniffing for Fart Clouds Around Distant Moons
NASA’s Europa Clipper launched in October 2024. It’ll reach Jupiter’s system in 2030 and make nearly 50 flybys of Europa, using radar to peer through the ice and analyze those water plumes. The onboard mass spectrometer will taste the chemistry—looking specifically for biosignatures like amino acids or lipids. If there’s life in Europa’s ocean, and if those geysers are connected to that ocean, we might literally fly through alien biology.
The European Space Agency’s JUICE mission (Jupiter Icy Moons Explorer) launched in April 2023. It’s targeting Ganymede and Callisto, both suspected of harboring subsurface oceans. Ganymede, Jupiter’s largest moon, generates its own magnetic field—unusual for a moon—suggesting a metallic core that could drive hydrothermal activity. JUICE carries a suite of instruments designed to detect organic molecules and assess habitability.
Meanwhile, back on Earth, astrobiologists are studying Lost City—a hydrothermal field on the Mid-Atlantic Ridge discovered in 2000. Unlike black smokers that spew superheated, acidic water, Lost City’s vents are alkaline and relatively cool, around 104-194°F. The chemistry there mirrors what we expect on icy moons. Serpentinization—water reacting with olivine-rich rock—produces hydrogen and methane without needing volcanic heat. It’s powered by tectonic forces, just like Europa’s ocean floor probably is.
So can life exsist in volcanic vents on other planets? The question isn’t really “can it.” The question is: how would we even recognize it if it’s been evolving independently for billions of years in alien water? Would it use DNA? Would it build cells? Would it metabolize anything we’d recognize as food?
Or would it be so fundamentally weird that we’d need to redefine what living even means?
