| Microbes thrive on iron under the ice|
|A colony of iron-breathing microbes has survived for millions of years under an Antarctic glacier, without air or sunlight, researchers report.|
The tiny organisms were probably trapped when the sea they were living in became sealed in the ice, and survived by decomposing the remains of other sea life, suggest the researchers in the journal Science.
"This gives us some insight into how life survives for extended periods of time in cold, dark conditions," says Dr Jill Mikucki of Dartmouth College in New Hampshire, who worked on the study.
Such creatures survive in extreme environments on earth and perhaps on other planets and moons, she says. "I think it can provide some insight into space exploration."
The microbes were found at Antarctica's Blood Falls, a frozen waterfall coloured bright red by iron, which attracted attention as early as 1911.
The colour comes from a very slow leak from a pool 4 kilometres beneath the ice, which is teeming with microbes, says Mikucki. They survive in a brine loaded with iron and sulfur.
"The brine comes out through some kind of crack," says Mikucki. "I got lucky one year and we were able to capture samples while it was actively flowing."
She was able to culture living microbes, including Thiomicrospira arctica, which metabolises sulfur, and Desulfocapsa sulfoexigens, which can live without oxygen.
Mikucki says it is not clear how many newly discovered species there may be.
"[It] is a unique sort of time capsule from a period in earth's history," she says. "I don't know of another environment quite like this on earth."
Assistant Professor Ann Pearson of Harvard University, who worked on the study, says, "It's a bit like finding a forest that nobody has seen for 1.5 million years."
"Intriguingly, the species living there are similar to contemporary organisms, and yet quite different - a result, no doubt, of having lived in such an inhospitable environment for so long."