Deep Impact: excavating comet Tempel 1. 
Deep Impact collided with comet Tempel 1, excavating a crater controlled by gravity.  The comet's outer layer is composed of 1- to 100-micrometer fine particles with negligible strength (<65 pascals).  Local gravitational field and average nucleus density (600 kilograms per cubic meter) are estimated from ejecta fallback.  Initial ejecta were hot (>1000 kelvins).  A large increase in organic material occurred during and after the event, with smaller changes in carbon dioxide relative to water.  On approach, the spacecraft observed frequent natural outbursts, a mean radius of 3.0 +/- 0.1 kilometers, smooth and rough terrain, scarps, and impact craters.  A thermal map indicates a surface in equilibrium with sunlight.