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Antarctica is home to some of the most alien places on Earth. No trees interrupt the horizon. The landscape, all sharp edges, seems to go on forever until it drops off dramatically into the frigid sea. Everything is quiet, save for the crackle of ice and gusts of wind, and unbearably cold.
John Priscu, a microbial ecologist at Montana State University, has visited Antarctica 40 times for research since the mid-1980s. When he first made the trip, scientists weren’t as worried about climate change as they are now. But these days, Priscu can feel the planet changing beneath his feet. The snow has become noticeably mushier, and driving equipment-laden tractors across the landscape feels like slogging through thick mud. Drills meant to probe icy depths instead get stuck in the slush.
For scientists like Priscu, the effects of a warming world reach far beyond our suffering planet. In Antarctica, the Arctic, and lower latitudes around the world, scientists use extreme environments to test ideas and techniques for ambitious space missions. Such places, known as analog sites, resemble environments on Mars and certain moons of Jupiter and Saturn—celestial bodies where microbial life may have once arisen, or may even be alive right now. Knowledge about the little organisms living in these strange places on Earth gets funneled into efforts to detect alien life elsewhere in the solar system.
If humans ever find evidence of extraterrestrial life, it will most likely be tiny and quiet, not a radio transmission from a distant civilization but perhaps a string of amino acids arranged in a familiar way in a chunk of ice. Humankind’s space-exploration talents are the sharpest and cleverest they’ve ever been; we have managed, from afar, to fly a helicopter in the Martian sky, sidle up to moons of Jupiter, and change the orbit of an asteroid. There’s never been a better time to find proof, once and for all, that life managed to spark somewhere other than on this planet. But climate change is melting away the rare places on Earth that could help astronomers make that historic discovery.
Scientists did not seriously consider the possibility that life could survive on inhospitable alien worlds until they found ecosystems thriving without sunlight or significant oxygen right here on Earth. In the mid-20th century, they detected microbes within the rock of Antarctica’s dry valleys. In 1977, marine creatures were discovered around hydrothermal vents deep in the Pacific Ocean. Priscu has sampled several subglacial lakes in Antarctica, drilling through the ice to reach secret realms of life that have been swirling in peace for millions of years.
Similar communities may exist in oceans beneath the icy exteriors of Europa, a moon of Jupiter, and Enceladus, a moon of Saturn. Antarctic lakes provide necessary practice for missions to sample those oceans. But Antarctic ice is thinning rapidly. If it softens enough to expose Priscu’s lakes to cold air—an ever-likelier possibility in a warming world—the hidden water could freeze solid. “We need to get into these deep subglacial lakes in Antarctica while we still have them,” Priscu told me. “If we can’t develop the tools and the ability to drill through two miles of ice in Antarctica and sample an environment for life, we shouldn’t be spending billions of dollars putting a lander on Europa.”
Astronomers are intent on exploring Europa, in part because its surface is crisscrossed with reddish streaks that suggest the presence of sulfur, which is essential to life as we know it. In fact, Europa looks remarkably similar to Borup Fiord Pass, a site in the Canadian High Arctic where a natural spring spills out onto the ice, carrying sulfur from beneath a glacier. The spring is the only one of its kind on Earth, and NASA has relied on data gathered there to design a mission to Europa, scheduled to launch later this year. A century ago, Borup Fiord Pass likely had dozens of such sulfur springs, John Spear, a professor at the Colorado School of Mines who has conducted research at the site, told me. Now there’s just the one.
Scientists could re-create some alien conditions in the lab, but many of them would make for a poor substitute. The sulfur-loving bacteria at Borup Fiord Pass, for example, produce an unpredictable assortment of compounds that’s difficult to mimic artificially. “There are so many possibilities and random things that happen in microbiology and geochemistry,” Spear said. “We can’t duplicate that in a synthetic environment.”
In Greenland, melting has made researchers question whether they’re getting the best results. The ice sheet there is regarded as one of the best analog sites for Enceladus, Michael Malaska, a planetary scientist at NASA’s Jet Propulsion Laboratory, told me. Enceladus sprays icy particles into space through cracks in its surface, and some of the material lands back on the moon’s surface and eventually stacks up. Malaska and his colleagues practice searching for life there by shooting lasers into the Greenland ice and looking for the telltale glow of amino acids in complex organic molecules. It’s a proof of concept for similar instruments on a potential mission to Enceladus. Surface temperatures on that moon are astoundingly cold—about –330 degrees Fahrenheit—so Malaska needs his analog sites to be as chilly as possible. Warmer conditions can reorganize any organic material in the snow, hindering Malaska’s efforts to interpret his results.
Even in warmer environments, fading ice has been a blow to astrobiologists. Pascal Lee, a planetary scientist at the SETI Institute, laments the loss of analog sites in volcanic caves in Hawaii. As on Earth, flowing lava on Mars carved out empty underground caverns. Steam from volcanic eruptions could eventually have settled there and accumulated into ice as conditions grew colder. Some scientists think that Martian life may have migrated to these caves after the red planet's oceans evaporated into space. Lee describes Earthly look-alikes of these spots as the “holy grail” in the search for life on Mars. Lee said that a few remain in Iceland, but in Hawaii, the air that flows into the analog caves from the surface is now so warm that nearly all of them are ice-free.
Lee has faced different challenges at his field sites in the Arctic. About 15 years ago, he and his team drove across the sea ice of the Northwest Passage in winter, sampling the snow as they went to study how human-designed missions might contaminate promising sites in space. Their truck almost went through the ice then, and the landscape is now so slushy that Lee says he wouldn’t try to repeat the expedition, even in the heart of winter. “Climate change has essentially rendered this kind of study really dangerous,” he told me. In Canada’s British Columbia, longer and more intense fire seasons have created problems for Darlene Lim, a research scientist at NASA. Even a distant wildfire can affect air quality enough to prevent Lim from bringing her teams to Pavilion Lake, home to a microbial community thought to resemble some of Earth’s earliest life-forms. “Every time I have the privilege of going into one of these environments, I have to do a bang-up job,” Lim told me. “I have to make sure that I optimize my trip to get all the data I could possibly get,” because she doesn't know if smoke or other hazards could someday keep her from coming back.
Analog sites don’t only inform mission designs and the interpretation of data from space. They also expand scientists’ imagination for what kinds of extraterrestrial life are possible. In 2017, researchers dropped a camera-carrying robot into a hole in a floating glacier in the Arctic and discovered a community of corals, worms, anemones, and other creatures, a metropolis hidden beneath the frozen landscape. Microbial ecologists hadn’t seen anything quite like it before.
A few years later, nearly half of the ice sheet collapsed into the ocean, dragging the habitat away with it. How many more hidden worlds might be lost to our metamorphosing climate before we get the chance to understand them? The faster that extreme ecosystems disappear from our planet, the more limited astronomers’ concept of life may be, raising the risk that we overlook a faraway spark somewhere else. No amount of sophisticated scientific instruments can make up for that.
