Research on cold-loving Earth organisms is especially valuable, McKay says, because "all the places in the solar system that may harbour life" – like Mars and Europa – "are cold and icy".
Salt of the Earth
Despite its name, the Dead Sea does harbour life. It's the saltiest body of water on Earth, but a few microbes thrive there, in water eight times saltier than the ocean. Scientists studying one of them, Haloarcula marismortui, discovered that it has specialised proteins that protect it from the effects of salt.
Scientists have theorised that any microbes living on Mars would have to be something like terrestrial halophiles in order to cope with the planet's high salinity.
However the results of recent explorations by the rover Opportunity, which found magnesium sulphate deposits that may have been left by salty water, have some scientists saying Mars may have been too salty to sustain any kind of life.
Other scientists say it's too soon to draw that conclusion, however, and McKay says there are probably regions on Mars that were not as harmful to life. "It can't be too salty everywhere," he told New Scientist.