Only the most hardened organisms can thrive in one of the coldest springs on Earth. So in the summers of 2017 and 2019, Lyle Whyte took a helicopter to Lost Hammer Spring in the unpopulated High Arctic of Nunavut, Canada. Snow, ice, salted tuff, rocks and permafrost surround the humble spring, which is nestled among nearly barren, treeless mountains on Axel Heiberg Island, a few hundred miles from the North Pole. He had traveled to this alien place to study the microbes that live in the salty, icy, oxygen-deficient water in the hopes of learning what life would have looked like if it ever arose in similar places — on Mars.
In a new newspaper in The International Society for Microbial Ecology JournalWhyte and his colleagues write that the microorganisms that live a few inches down in the spring sediment can indeed survive the harsh environment. Most terrestrial species depend directly or indirectly on solar energy. But these microbes can survive on a chemical energy source: They eat and breathe inorganic compounds like methane and hydrogen sulfide, making the area smell like rotten eggs even from a distance. (The research team pilot calls the site the “stinky springs”.) “You have these rock-eating insects, essentially, eating simple inorganic molecules, and they do this under very Mars-like conditions, in this frozen world,” says Whyte, an astrobiologist at McGill University in Montreal, Canada.
The search for extraterrestrial life has often focused on the Red Planet. Scientists believe that more than 3 billion years ago, Mars was warmer, wetter than it is today, and had a more protective atmosphere. Though the planet is now almost completely inhospitable to life, researchers envision Mars microbes from the past living — or even thriving — on the frigid, dirty bottom of a pond. Scientists have sent rovers to ride the surface to look for evidence of such long-extinct alien microorganisms, and a drone helicopter to explore the path ahead. But it’s expensive — and difficult — to send a sampling expedition to Mars. Canada is a lot closer, and it’s not a bad proxy.
The Lost Hammer Spring has some unique features that mimic parts of the Martian landscape, Whyte says. First, there is the sub-zero temperature (about -5 degrees Celsius), as well as the extreme salinity of the water – 25 percent salinity, about 10 times as salty as seawater. (The salt keeps the water liquid and prevents it from freezing.) Mars has been found to have salt deposits here and there, some of which may have been in brine eons ago, which might have been the last habitable places on the planet. The water at Lost Hammer contains almost no oxygen, less than 1 part per million, which is unusual on Earth, but not on other worlds. Any creature that persists there counts as an “extremophile,” because it survives in bleak conditions on the fringes of where life could exist at all.
On each of their trips to the remote Canadian region, Whyte and his colleagues scooped up samples of the briny mud, just a few grams each. Back in their lab, they used machines to isolate microbial cells and sequence their genomes and RNA to find out what the microbes use for energy and how they tolerate spring conditions. That could help astronomers’ efforts to figure out where and how microbes might be maintained on Mars or other worlds.