In this valley it is minus 35C and bone dry. It may hold a clue to life on Mars

Colonies of microbes thousands of years old have been found in the soil in one of the coldest and driest places on Earth.

Colonies of microbes thousands of years old have been found in the soil in one of the coldest and driest places on Earth.

The micro-organisms have been dug out of Antarctica's ice-free Dry Valleys, where the average temperature hovers around minus 35C (31F) and annual rainfall is virtually nil.

Scientists said the penicillin-like bacteria and colonies of microscopic fungi, which live several inches below the soil surface, were the latest additions to a gallery of life-forms known as "extremophiles", which can survive the harshest conditions.

A team of researchers from the United States, Canada and New Zealand said their discovery supported the growing belief that extraterrestrial life might be able to survive the dry and cold conditions on Mars.

Writing in the scientific journal Icarus, the academics said the discovery opened up "the possibility of life on Mars and the possible positions within a soil where it might be found".

They added: "Our field-based investigation of parts of the Antarctic yields valuable information about soils and microbial life that may bear significantly on future manned and unmanned missions to Mars."

Previous studies have confirmed the presence of extremophiles living within a few millimetres of the surface of porous Antarctic rocks. But this is thought to be the first time that living fungi and bacteria have been found several centimetres below the surface of the Antarctic soil.

William Mahaney, a member of the team from York University in Toronto, said the survival of the microbes could stem from the extreme saltiness of the soil, which could be preventing any water from freezing.

"We sampled the lower-down, high-salt horizons [depths], where we thought we would find few micro-organisms. We found just the opposite," Dr Mahaney said.

"We found microbes in soil with 3,000 parts per million concentrations. That's like vodka. There's so much salt, temperatures can drop to minus 56C before there's frostbite," he said.

"The strange thing is, we found several colonies of Beauveria bassiana – fungi that thrive on insects. The colonies may have been there longer than centuries, maybe millennia, maybe since the last Ice Age."

Microbes living about a millimetre below the surface of Antarctic rocks are warmed by the sun and benefit from a "microclimate" that keeps them from freezing during the day. However, this is not the case for anything living several centimetres below the soil.

Professor Victor Baker, from the University of Arizona, said the availability of liquid water was crucial for life either on Earth or Mars and "supercooling" with the help of salt provided a possible solution to surviving extremely cold temperatures. "Although these supercooling processes are not fully understood on Earth, the fact that they occur in Antarctica shows the possibility that they also might occur on Mars," Professor Baker said.

Charlie Cockell, of the British Antarctic Survey in Cambridge, said it had been known for some time that the Dry Valleys of Antarctica were not completely dead, even though they seemed so unsuitable for life. "I think perhaps the most significant aspect of this research is that it shows the association between microbes and salt at way below the normal freezing point of water," Dr Cockell said.

Over the past decade or so biologists have discovered a range of microbes living in extreme environments, such as salty soda lakes or hot springs and geysers in volcanically active regions.

Monica Grady, a specialist in Martian meteorites at the Natural History Museum in London, said: "In the time between the emergence of life and the present day, microbes have colonised every environment in which it is possible for life to survive."