Hugh Pickens writes "New Scientist reports that instead of identifying chemicals that could point to life, NASA's robot explorers may have been toasting them by mistake. Even if Mars never had life, comets and asteroids that have struck the planet should have scattered at least some organic molecules over its surface but landers have failed to detect even minute quantities of organic compounds. Now scientists say they may have stumbled on something in the Martian soil that may have, in effect, been hiding the organics: a class of chemicals called perchlorates. At low temperatures, perchlorates are relatively harmless but when heated to hundreds of degrees Celsius perchlorates release a lot of oxygen, which tends to cause any nearby combustible material to burn. The Phoenix and Viking landers looked for organic molecules by heating soil samples to similarly high temperatures to evaporate them and analyse them in gas form. When Douglas Ming of NASA's Johnson Space Center in Houston, Texas, and colleagues tried heating organics and perchlorates like this on Earth, the resulting combustion left no trace of organics behind. "We haven't looked the right way," says Chris McKay of NASA's Ames Research Center. Jeffrey Bada of the University of California, San Diego, agrees that a new approach is needed. He is leading work on a new instrument called Urey which will be able to detect organic material at concentrations as low as a few parts per trillion. The good news is that, although Urey heats its samples, it does so in water, so the organics cannot burn up."