Rosetta, Chury and the Formation of Planetesimals
The question of how the first gravitationally bound bodies, the so-called planetesimals, formed in the young Solar System has not been completely answered. The recently completed Rosetta mission has provided us with a wealth of new information about comet 67P/Churyumov-Gerasimenko (Chury), which seem to indicate that the nucleus of comet 67P is a pristine body that formed by the gentle gravitational collapse of mm- to cm-sized dust aggregates. This formation scenario can also explain many (albeit not all) of the observed properties of comet 67P. Future missions to comets will greatly benefit from Rosetta's observations by performing dedicated investigations concerning the origin of comets.