astroengine writes: Scientists have solved the mystery of why the comet being studied by Europe's Rosetta spacecraft is shaped like a rubber duck — it started off as TWO separate comets, a new study shows. Ever since Rosetta sent back pictures of its twin-lobed target more than a year ago, scientists have debated whether the comet, known as 67P/Churyumov-Garasimenko, could be the result of two comets that merged together during the solar system's early years. The other option is that the so-called "neck region" between 67P's two lobes experienced some particularly active and still unexplained outgassing over the eons, eroding its more spherical shape into a body that resembles a rubber duck. "Our study rules out the possibility that the comet shape is the outcome of erosion," planetary scientist Matteo Massironi, with the University of Padova in Italy, wrote in an email to Discovery News. Rather, the neck region is where two independent bodies collided, analysis of high-resolution images taken by the orbiting Rosetta spacecraft shows.