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Antarctica; a world of living ice

Since his first trip in 1984, AAAS Fellow John Priscu has spent almost seven years of his life in Antarctica studying the little organisms living inside the ice sheet. (Photo: John Priscu)

When John Priscu looked out the window of the military aircraft taking him on his first trip to Antarctica, all he saw was white "dead" ice. But now, almost 30 years later, he knows that the ice he saw is actually teeming with life.

"I went down there for the adventure," says John Priscu, a professor of Biology at Montana State University and a fellow of AAAS, "and I'm still having an adventure. I still am drawn to the science because I can't figure these systems out."

The microbes living within and beneath the ice are teaching us about how life can exist at extremes — not only here on Earth but in the Solar System. But they are still hard to study. And we are just starting to understand the elaborate ecosystems that live in the ice, Priscu explains, adding that it was a laughable idea just a decade ago that life even existed in this cold world.

When ice crystals form there are small spaces where they meet, called veins. These are about five to 50 microns wide, a space a little smaller than the diameter of a human hair. Most microbes are only a little over a micron long, so it is plenty of space for them to make a living. More than that, these veins contain liquid water for the microbes to use to drive their metabolism. Also, when the great pressures within the ice sheet change snow to ice, the impurities found in snow are pushed into the veins. These impurities — things like organic carbon and inorganic nutrients — are a perfect food sources for little microbes.

"So we have a nutrient rich environment, that's pretty salty," summarizes Priscu. "And it's got a low Ph and it's cold, subzero." Priscu notes it's not the most hospitable environment, but it is more welcoming for the little microbes than the extremely cold, dry and radiation-baked surface of the continent.

Much is still unknown about the microbes, partially because they occur at much lower densities than we see in the open ocean, and because it is logistically difficult to sample this icy world. We do know that the microbes are blown there from places as far away as South America, Australia and Africa. It could be they are just hanging out in the ice, sustaining themselves until they get to the bottom of the ice sheet where it's warmer and pools of liquid water are present. But genetic testing suggests that many of the microbes found in the Antarctic ice sheets are very similar to those found in other subzero systems, which indicates that these microbes could be growing and multiplying rather than just freeloading in the ice.

Genetic evidence also indicates that some of the microbes — especially those that live at the warmer bottom layers of the ice — work with others in a consortial relationship. Certain microbes are able to mine the minerals in the rocks under complete darkness and use these minerals as an energy source to transform carbon dioxide into cellular matter, the same way plants use the sun for energy above the ice, explains Priscu. These microbes then produce organic carbon and inorganic nutrients as a byproduct, which become food for other microbes — just as plants produce organic carbon that provides fuel for animals on the sunlit portions of Earth.

"In these harsh environments, one bug's poison is another bug's food," says Priscu. When things are tough, they have to rely on one another to survive.

But Antarctica's remoteness, extreme cold and lack of sunlight for much of the year doesn't make research easy for those scientists such as Priscu. It took Priscu and his teams many years to obtain funding for projects during the Antarctic winter. And then there is the mental toll of working in Antarctica.

"In 1995," recounts Priscu, "we spent an entire September where the high temperature was -47 Celsius and the low was -55 Celsius and darkness prevailed over daylight. We worked in it every day, despite the extremes. It's hard. But we learned a lot." Priscu has spent 28 field seasons in Antarctica since his first trip in 1984. That's added up to about seven years of his life on a continent where the lowest temperature ever recorded was -89 Celsius at Vostok Station, according to NASA.

Antarctic research has import well beyond the ice sheet. The microbes they are studying in the ice provide information on their potential role in global biogeochemical processes. They also give us a hint about what potential life might look like on other icy worlds in our Solar System.

Part of Curiosity's mission, the most recent rover NASA sent to Mars, is to look for signs of life on Mars, either still living or from long ago. Most importantly, it is looking for the basic elements we think are essential for life, namely liquid water, some source of energy and carbon-based compounds to serve as building blocks. So the elements the microbes need to live in Antarctica are a great model for what to look for in order to find other organisms in the solar system.

Antarctica is also critical to our own planet's climate. With an area that is about one and a half times larger than the United States, Antarctica plays an essential role in how air and water circulate around the globe, and can give us important information about climate change. We still don't know all of the mechanisms of how ice is lost in Antarctica, or the extent of this process in the past, but understanding these dynamics will help us anticipate what future climate change could bring.

"It's so important with climate," says Priscu, "because about 70 percent of the world's fresh water is locked up as ice down there. And if Antarctica melts, the ocean is going to go up by about 60 meters. Given the high population density of humans in coastal regions of our planet, it's not going to be a pretty thing".

There is also a world underneath Antarctica's ice which is still largely a mystery to us. At the bottom of the ice sheet, Antarctica is warmer. It is heated by Earth's geothermal core and insulated from the cold air above it by more than a mile of ice. Using satellites, scientists have identified more than 200 liquid water lakes, some more than two miles under the ice. We can watch rivers flow beneath the continental ice sheet, unseen except for undulating ripples across the surface of the ice sheet caused by water flowing below. Following more than 10 years of planning, teams from Russia, the United Kingdom and the United States plan to directly sample subglacial lakes in January 2013. After many years of drilling, the Russian team hopes to obtain lake water from Lake Vostok, one of the largest lakes on our planet, which has depths that haven't seen a ray of sunlight for perhaps 15 million years.

Priscu is heading a U.S. team that plans to drill into Subglacial Lake Whillans, a lake dominated by subglacial rivers.  "We don't know what we'll discover in that water, but we know it will be something new. We will also learn a great deal of how subglacial lakes and rivers control subglacial biogeochemistry and the flow of Antarctic ice to the southern ocean," he said.

All of this time at the bottom of the world has taught Priscu a lot about human nature. He has learned how to keep his fellow researchers having fun, how to keep the work serious, but how to play too. Some people still don't do well, he says, but others come to love the solitude.

"I'm still doing it," says Priscu, now 60. "Still sleeping in tents and enjoying the high energy and the young people. It is funny how generations change — I have to share my music; they don't like Jimi Hendrix, Janis Joplin and Led Zeppelin as much as I do. But that's ok."


Rebecca Riffkin