Glacial lake hides bacteria
Icelandic colony makes a splash in Mars debate.
Scientists have discovered a community of bacteria living in the lake beneath an Icelandic glacier. The chilly world provides a model of martian terrain and may boost speculation about the red planet's potential inhabitants.
This is the first unequivocal example of life in a subglacial lake. "Yet another habitat on Earth that could be colonized by microbes, is colonized by microbes," says Eric Gaidos from the University of Hawaii, who was part of the research team.
The Icelandic bacteria live in a cold, dark lake, nestling inside the crater of the Grímsvötn volcano. The lake, which is up to 100 metres deep, is covered by a 300-metre thick ice-sheet, but heat rising from the volcano below stops it from freezing entirely.
"We know for certain there is ground ice on Mars," says Gaidos. "We suspect there were glaciers, and we are fairly confident there is volcanism." So if there is life on Mars, subglacial lakes warmed by volcanoes are a likely place for it to persist.
Gaidos presents the research1 today at the Bioastronomy 2004 conference in Reykjavik, Iceland.
The team used a drill that fires near-boiling water to bore a hole through the glacier. Five days later they broke through to the lake, and lowered a bucket to bring water to the surface. The water contained bacteria whose genetic make-up turns out to be similar to cold-loving bacteria that are often found in snow.
The scientists also took a DNA fingerprint of the entire ecosystem to prove that the bacteria they found in the lake were different from those found in the snow above the glacier. The bacteria were definitely not introduced from above, insists Brian Lanoil, a geomicrobiologist from the University of California, Riverside, who is also part of the research team.
Researchers have also found bacteria in ice cores taken from Antarctica's Lake Vostok, the largest subglacial lake in the world. But it is possible that the microbes hail from elsewhere and were transported to Lake Vostok as the glacier moved across the Antarctic. This is the first time that bacteria have been found in subglacial water, says Lanoil.
The Icelandic environment could even surpass Lake Vostok as a model for extra-terrestrial habitats. Although the Antarctic lake is thought to be full of oxygen, the Icelandic water contains surprisingly little of the gas.
It also contains few of the sulphurous salts normally found in volcanic lakes. "But the bacteria have the nutrients they need to sustain an ecosystem," says Lanoil. The microbes gather the carbon they require by absorbing carbon dioxide dissolved in the water. They ultimately get their energy from chemicals released during geothermal activity, rather than by absorbing light from the Sun.
The scientists could even grow some of the Icelandic microbes in the lab by keeping them cold and dark. They now hope to investigate other subglacial lakes in Iceland to investigate whether different communities can evolve at different locations.s
- Gaidos E., et al. Astrobiology, (in press).
- Sharp M., et al. Geology, 27. 107 - 110 ( 1999).
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