Vol. 557
In section 10. Planets and planetary systems

Beginning of activity in 67P/Churyumov-Gerasimenko and predictions for 2014-2015

67P/Churyumov-Gerasimenko is a particularly important comet because it is the target of the ESA Rosetta mission, due for rendezvous next year. How the comet became active is a major puzzle to be solved by the mission. The authors use difference image analysis data taken between 2007 and 2010 to determine precisely when it became active. They determine that this occurred in November 2007, when the comet was still at 4.3 AU from the Sun. Assuming that the rise in activity will follow the same pattern at the next revolution, the comet should become active again in March 2014. This is very early in the schedule of the Rosetta mission, because it corresponds to the time when the spacecraft will be recommissioned following deep-space hibernation. Early observations from the spacecraft and from Earth would be highly desirable. The authors also predict that a small fraction of the comet surface (from about 1.4% up to 4% at perihelion) should be active, a prediction that will be directly tested by Rosetta.