Cue "X-Files" music: Maybe we do need to worry about those contrails snaking through the skies overhead. For years, contrail conspiracy theorists have competed with UFO sighters and alien abduction survivors for air time on late-night radio's "Art Bell Overnight." Their claim: Those puffy, white jet wakes are no mere water vapor, but chemicals sprayed by the government to (a) kill us, or (b) activate mind control chips secretly implanted in our bodies. Laughable? Why then has NASA launched a project to engage ordinary citizens - even schoolkids - in monitoring the jet fuel leavings? In a word: climate. NASA scientist Lin Chambers is a principal investigator with CERES, a satellite project that monitors the impact of contrails - essentially man-made clouds - on the Earth's radiant energy systems. Early evidence suggests that lingering contrails affect surface conditions in two ways, particularly in areas below major air corridors.