Aboveground, Antarctica appears barren and sterile. But tucked within warm pockets of volcanic ice caves, diverse plant and animal life may flourish. Steam and gas spewed by active volcanoes at Mount Erebus on the continent's Ross Island, and at three volcanoes on nearby Victoria Land, have carved out heated oases in ice domes, towers and cave systems.
"The caves are covered with ice, and there's ice all around, but some are as warm as a summer's day — over 20 degrees Celsius [68 degrees Fahrenheit]," Ceridwen Fraser from Australian National University's Fenner School of Environment & Society tells HowStuffWorks via email. "In most, it's pretty dark as not much light gets through the thick ice, but in others, where ice cover is thin, light can filter through."
It's in these caves that Fraser's research team collected soil samples that yielded the DNA of dozens of plant and animal species. Most of the DNA collected from the caves match with species of, say, moss, algae and nematodes already detected at other sites on the continent. But Fraser says the team also identified genetics of life that may be unique to the unusual environment of the volcanic ice caves.
"There were some sequences that didn't make a close match to DNA in online databases ... which makes me wonder if there might be species that are specially adapted to the caves and found nowhere else," Fraser says. "It opens up the doors to some exciting discoveries about biodiversity in Antarctica."
While the DNA captured from the volcanic areas did not conclusively prove that the sites host living forms of the plants and animals, the samples nonetheless offer a tantalizing glimpse into what forms of life might live there. The researchers' next step will be to find direct evidence — namely, the life itself — in samples.
Looking for Life in All the Hard Places
Getting samples from the Antarctic volcanic sites is no easy task. Laurie Connell, a researcher in molecular and biomedical sciences at the University of Maine, is a co-author of the study that led the team to the geothermal sites. The journey "takes a lot out of you," she says in a phone interview. Once the researchers reached the continent, they were flown by helicopter part way up Mount Erebus. They stayed in tents at least two nights to acclimate to the higher elevations, and from there they either hiked or snowmobiled to the ice cave hollows.
At one point Connell and her colleagues were forced to ride out a blizzard and spent four long days stuck in their tents as wind and snow howled outside. Since conditions were so harsh, they couldn't leave the tents to go to the bathroom ("We had a poop bucket in the tent," Connell says) or to access their food stash.
"It was over Thanksgiving so we decided to save our remaining dry soup mix and crackers for Thanksgiving day," Connell says. "When we woke up on Thanksgiving for our 'feast' and made our soup, we realized our hot water was no longer hot—just tepid. It was pretty pathetic."
Once the researchers managed to reach the field station at the volcano Mount Erebus, where temperatures away from the geothermal sites get to minus 30 degrees Fahrenheit (minus 34 degrees Celsius), the team fanned out to various sites and used ropes and harnesses to access a range of geothermal features. The features included areas of soil that were heated from the volcanic activity, but still exposed; "ice hummocks," which are domes of unstable ice covering a heat-spewing volcanic vent; and ice towers and caves that presented intricate labyrinths of icy underworlds.
Among the unidentified DNA recovered at the volcanic sites, the closest match the scientists could find are arthropods. This category of animals features external shells and jointed limbs, and includes over a million known species, ranging from lobsters to centipedes to microscopic copepods.
Arthropods have been found elsewhere on the Antarctic continent, including on patches of exposed ground that make up the mere 0.3 percent (or less) of Antarctica that is not covered with ice. In these regions, life has to contend not only with extreme cold, but also with extreme dryness. Even though much of the continent is coated in ice that is up to 3 miles (5 kilometers) thick in parts, Antarctica's inner regions receive an average of only 2 inches (5 centimeters) of precipitation — primarily snow — each year.
But despite the harsh conditions that exist away from its coast, Antarctica hosts vast biomes under the ice that scientists are now exploring.
A Desert Teeming With Organisms
"We think of Antarctica as a wasteland," Fraser says, "but even in that extreme environment life thrives in amazing places—on rocks on top of mountains, in the lower layers of sea ice, in dry 'deserts'—why not also in these warm, hospitable caves hollowed out by steam between the ice and the rock?"
In East Antarctica, Lake Vostok is buried under 2.3 miles (3.7 kilometers) of ice and hasn't been near open air for some 15 million years. Samples taken from the lake in an unrelated study yielded genetic sequences for 3,507 recognizable species, according to a 2013 study, as well as about 10,000 species not yet known to science. Scientists have also found hardy forms of bacteria within networks of salty liquid water discovered at Antarctica's McMurdo Dry Valleys, which feature striking, blood-red falls of iron-rich outflow.
However, scientists must be mindful of whether the DNA they find at these extreme Antarctic sites represents life that truly exists there, or organisms that were transported in and persisted only temporarily. "Organisms could be transported aerially — especially microbes and spores — or by inadvertent contamination of clothing, scientific gear, etc.," says Bradley Tebo, a professor at Oregon Health and Science University who has also gone on expeditions to take samples at Mount Erebus.
Indeed, Connell says her team was aware that a British group summited Mount Erebus over 100 years ago and visited many of the sites where they took their samples. Six men from the team of British explorer Robert Falcon Scott ventured up the 12,448-foot-tall (3,794-meter-tall) volcano in 1912 to collect geological specimens and do surveys of the region.
"We found fragments of ash trees and other things that they likely had in their equipment," Connell says. "So one of our questions is which of the DNA represents things that were left over from these very early expeditions to Antarctica and which may represent life there now?"
Still, the DNA discoveries at Mount Erebus may only represent a fraction of diverse life housed within its volcanic ice caves. Antarctica is home to more than 100 volcanoes, each of which may host its own network of ice caves and tunnels.
"We don't yet know just how many cave systems exist around Antarctica's volcanoes, or how interconnected these subglacial environments might be," Charles Lee, another co-author of the research, said in a statement. "They're really difficult to identify, get to and explore."
Antarctica may be difficult to get to and explore, but there are even more challenging places. Many scientists believe understanding the life and its subsurface environs in the harsh climate of Antarctica could lend clues to possible life on places in even more extreme locations — like Mars.
"This research, and other research indicates that volcanic activity can foster life in extreme conditions," Fraser says. "And yes, there is the potential that around volcanoes on other planets and moons we might find life, even when exposed atmospheric conditions are harsh."