New Signs of Polar Life
|Hypoliths colonizing an Antarctic rock. Credit: BAS|
Large colonies of micro-organisms living under rocks have been discovered in the most hostile and extreme regions of the Arctic and Antarctic – giving new insights on survival of life on other planets.
Reporting in this week’s Nature, scientists from British Antarctic Survey (BAS) and Scripps Institution of Oceanography reveal their surprise findings that rock-dwelling micro-organisms can photosynthesise and store carbon just as much as the plants, lichens and mosses that live above ground. Less than 1.2 percent of the Poles are covered in vegetation, yet over 90 percent of the rocks studied were colonized.
BAS microbiologist Dr Charles Cockell says, "Although it’s usual to find micro-organisms thriving under quartz and translucent rocks in hot deserts because enough light gets through, we wouldn’t have expected this type of colonization in the polar regions where most of the rocks are opaque. Also, the harsh UV- radiation and violent winds make for a hostile environment. We found that in fact the opaque rocks protect the micro-organisms and, the movement of rocks during the annual freeze-thaw allows cracks to form and light to penetrate beneath the surface. " Rocks were sampled from Cornwallis Island and Devon Island in the Canadian High Arctic and Mars Oasis on Alexander Island on the Antarctic Peninsula.
The paper, ‘Widespread colonization by polar hypoliths’ by Charlie Cockell (BAS) and M. Dale Stokes (Marine Physical Laboratory, Scripps Institution of Oceanography) is published as a brief communication in the journal Nature on 23 September 2004. The British Antarctic Survey is a leader in research into global issues in an Antarctic context.
|Antarctic changing landscape. Coldest surviving organisms: 5 F (-15 C) Cryptoendoliths|
"This shows us that places we may think of as extreme – for example other planets like Mars – could nurture surprising habitats for life. The Poles are not the barren wilderness, devoid of life as we previously thought".
The global picture of Mars is sometimes compared terrestrially to Antarctic dry regions, only colder. The current martian atmosphere is 99% thinner than the Earth’s. The surface temperature averages -64 F (-53 C), but varies between 200 below zero during polar nights to 80 F (27 C) at midday peaks near the equator.
Astrobiologist, Dr. Chris McKay of NASA Ames has pointed to Antarctic dry valleys, in particular to Lake Vanda and the Onyx River, as useful guides for a terrestrial tourist looking for Mars analogues. "I would argue that the most relevant environment [to Mars] is the dry valleys of Antarctica. This is the largest ice-free region in Antarctica. The average temperature is minus 20 C (minus 4 F). Summertime temperatures are higher. Precipitation is equivalent to one or two centimeters per year of moisture. And the pressures are well above the triple point of water. [The triple point of water is a combination of temperature and pressure that enables water to exist in all three states: solid (ice), liquid and gas (water vapor). When atmospheric pressure is too low, as on the surface of Mars today, water cannot exist in liquid form, regardless of the temperature.]"
While such a place seems austere or permanently locked in a frozen state, "What’s interesting about this environment," said McKay, "is that because it’s so dry, it’s dead. There’s nothing growing on the surface soil. Precipitation is too slight. It evaporates, blows away. This is one of the most lifeless places on Earth. But in the water in Lake Vanda, underneath the ice, there are thick mats of algae and bacteria. So here in this Mars-like environment, where the average temperatures are minus 20 C (minus 4 F), there’s still a hydrological cycle, based on snow, glaciers, melt and accumulation in ice-covered lakes".
|Liquid water may have flowed episodically over the surface of Mars in the planet’s distant past. Artist conception of a delta filling a crater.
Back at Mars’ mission control (the Jet Propulsion Lab) Antarctica is also a favorite topic. Scientists have devised a system of naming features on Mars that serve as labels borrowed from such interesting places in Antarctica. After the two robotic rovers landed on Mars in January, Dr. Jim Rice, a geologist at Arizona State University and a rover science team member, suggested that features studied during the mission should be named according to a theme. Principal investigator Dr. Steve Squyres, a geologist at Cornell University, said, "OK, you’re in charge."
"Let’s see, then we also had Lake Vanda," said Rice. "That’s an ice-covered lake in Antarctica."
"That was kind of neat," Rice adds, "because both Steve and I have done scuba diving in ice-covered lakes in Antarctica. Opportunity recently discovered that a lake once existed in the Meridiani Planum region. I think that Martian lakes most likely did have ice covers on them."
There’s also "Fram Crater," named after a ship used by Norwegian explorer Roald Amundsen. Fram means "forward" or "onward" in Norwegian. "Fram was a famous scientific vessel that conducted an awful lot of important work in the Arctic," said Rice, "but it’s most famous for taking Amundsen and his team to Antarctica where he led the first team to reach the South Pole on December 14, 1911."
As Rice noted: "Whenever explorers go somewhere, we always want to name things. Everybody on this team has named at least one thing, I think it’s safe to say, on this mission, one way or the other now. It just makes it more personal. It allows one to leave their little mark on the surface of another planet…So you give it a name. It’s just something we humans like to do."