The global shape, density and rotation of Comet 67P/Churyumov-Gerasimenko from preperihelion Rosetta/OSIRIS observations

Abstract

Comets constitute a large population of objects formed at the early stage of the formation of the Solar System and partially preserved in the Kuiper belt and in the Oort cloud. The present physico-chemical properties of these bodies result from a long and complex history of dynamical, collisional, and chemical evolution. In particular, the sublimation of ices trapped in the nuclei is expected to significantly alter their surface properties as they periodically come close to the Sun. The detailed study of individual comets is therefore expected to give new insights into these processes and to shed light on the processes which led to their formation in the solar nebula. Rosetta is an ESA-led mission, one of the cornerstone missions of ESA’s “Horizon 2000” scientific program, whose ultimate aim is the in-depth physico-chemical characterization of the surface and interior of a comet nucleus in order to understand the processes which led to the formation of the planetesimals in the early Solar System. In complement, the Rosetta mission has also been designed to shed light on the physical processes at the origin of cometary activity and on those which drive the evolution of comet nuclei. The Rosetta spacecraft was launched in March 2004 to perform a rendezvous with the Jupiter-family Comet 67P/Churyumov-Gerasimenko (hereafter “67P/C-G”) in 2014 and to escort it throughout its 2015 perihelion passage and beyond. After two encounters with Asteroids 2867 Steins and 21 Lutetia, the spacecraft was put in hibernation between June 2011 and January 2014, and successfully re-activated on January 21, 2014.