The Subsurface Structure of Comet 9P/Tempel 1 Projected into the Dust Plume

Cometary nuclei are believed to contain important information on the condition of the solar nebula, but little observational data is available on their interior structure. Our ground-based observations of NASA’s Deep Impact event and the cratering mechanism show that comet 9P/Tempel 1 has a surface layer consisting of small (submicron to micron-sized) carbonaceous grains whose thickness is a few tens of cm.