Physics and Astronomy Calendar

It is widely accepted that comets contain the most primordial material accessible in the solar system and that they provide major constraints on the conditions in the protoplanetary disk. It is also widely accepted that the outer layers of a comet are highly evolved and does not represent the original material of comet nuclei. The major gaps in our understanding of cometary nuclei can be addressed only by probing the nucleus to depths of tens of meters. This has been done on July 4, 2005 by hitting comet 9P/Tempel-1 with the 360-kg impactor during the Deep Impact space mission. The collision of the impactor with the comet resulted in a huge cloud of excavated material that was observed not only from the flyby spacecraft but also from the Earth by ground-based and space telescopes. I present the main results of the Deep Impact mission obtained with the spacecraft instruments (high-resolution camera, medium-resolution camera, and infrared spectrometer) as well as ground based, Spitzer, and HST telescopes. The emphases are made on properties of the nucleus and the dust in the ejecta cloud. The latter has been the subject of my research. Finally, I briefly describe the plans for the extended Deep Impact mission.