This is a closer view of Comet Encke's collision with a Coronal Mass Ejection (CME) as seen by the STEREO satellite on April 20, 2007. The collision is notable because it completely removed Encke's tail. The blue color here is a gradient added to help make the comet and CME more visible.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 18.104.22.168.0