Rotation of Comet Hartley 2 from Structures in the Coma
  The CN coma structure of the EPOXI mission target, comet 103P/Hartley 2, was observed during twenty nights from September to December 2010. These CN images probe the rotational state of the comet's nucleus and provide a ground-based observational context to complement the EPOXI observations. A dynamically excited cometary nucleus with a changing rotational rate is observed, a characteristic not seen in any comet in the past. The lack of rotational damping during the four-month observing interval places constraints on the interior structure of the nucleus. 
Nalin H. Samarasinha, Beatrice E. A. Mueller, Michael F. A'Hearn, Tony   L. Farnham, Alan Gersch
astro-ph.EP