Persistent meteor trains, studied for more than a century, remain somewhat mysterious <Newton, 1869; Trowbridge, 1907; Chapman, 1955; Hapgood, 1980>. The Leonids meteor showers of recent years afforded opportunities to apply new research technologies, including lidars and sophisticated cameras. Here we explore a particularly curious but common feature: double trains. Since the traditional hollow cylinder explanation has been shown to be untenable, we suggest a new explanation, arguing that one train is due to gaseous vapor train emissions behind the meteor while the other is due to heterogeneous chemistry associated with recoagulated dust. In this model the separation is caused by gravitational sedimentation of dust particles, an idea supported by rocket-based observations of recoagulated dust behind a meteor, by rocket-based observations of enhanced sodium emissions in a dust layer, by rocket observations of a dusty trail, and by recent theoretical estimates of chemical reactions on dust.