Could bacteria exist on Europa?

The research findings are published in the latest edition of the journal Science. They reveal that populations of living bacteria have been discovered in water pockets embedded two metres (six feet) deep in solid ice.

No one knew the Antarctic bacteria existed until they were found by a team of experts led by Stephen Giovannoni, associate professor of microbiology at America's Oregon State University.

"This is a very barren environment with virtually nothing we usually associate with living organisms," said Professor Giovannoni. "But these photosynthetic cyanobacteria are alive, self-sufficient and growing. They have their own little world there we knew nothing about."

New hope of life on Mars

Mars, which once had extensive water, is dry and cold with temperatures ranging from minus100 degrees Celsius to freezing point.

Europa is believed to have a subterranean ocean of water or slush, warmed by Jupiter's gravitational tidal forces, beneath a shell of ice.

Professor Giovannoni said: "We're learning that the world is full of bacteria we know virtually nothing about. I could probably isolate a new, previously unknown bacterium from the sole of your shoe."