Comet reveals its secrets (September 2005) - News - PhysicsWeb

They also report that Tempel 1 consists largely of extremely fine particles that seem to be very loosely bound together: in other words, the comet is more like a pile of powder than a solid rock. The outer layer of the comet is composed of particles that are between 1 and 100 microns in size, while the density of the nucleus is about 600 kilograms per cubic metre (Sciencexpress 1118923).

In addition to the material ejected by the impactor, the flyby spacecraft also saw shallow outbursts of material - probably triggered by sunlight - with a mean radius of about 3 kilometres. This ejected material mainly contain water and carbon dioxide. Furthermore, a relatively high concentration of organic material, such as formaldehyde and methanol, was found to be more abundant than water and carbon dioxide during and after the impact.