Minute traces of specially designed greenhouse gases can be used to heat up Mars and make the planet habitable much faster than anyone thought possible. "On the Earth these gases may be pollution, but on Mars they are medicine,' says Chris McKay, who organised a meeting at the National Aeronautics and Space Administration's (NASA) Ames Research Centre in California, usa . No terrestrial life can survive in the bitterly cold and harsh environment of Mars. According to some scientists, 20 nuclear-powered factories could produce enough of these greenhouse gases to warm Mars by 5