When NASA's Deep Impact probe collided with Tempel 1, a bright,
small flash was created, which rapidly expanded above the surface
of the comet. This flash lasted for more than a second. Its overall
brightness is close to that predicted by several models.
After the initial flash, there was a pause before a bright plume
quickly extended above the comet surface. The debris from
the impact eventually cast a long shadow across the surface,
indicating a narrow plume of ejected material, rather than a wide
cone. The Deep Impact probe appears to have struck deep,
before gases were heated and explosively released. The impact
crater was observed to grow in size over time.
A preliminary interpretation of these data indicate that the upper
surface of the comet may be fluffy, or highly porous. The observed
sequence of impact events is similar to laboratory experiments using
highly porous targets, especially those that are rich in volatile
substances. The duration of the hot, luminous gas phase, as well
as the continued growth of the crater over time, all point to a model
consistent with a large crater.
This image was taken by Deep Impact's medium-resolution camera.
