Posted: Mon, Jul 11, 2005, 8:33 AM ET (1233 GMT)
Comet Tempel 1 released far more dust than scientists expected when a probe released by NASA's Deep Impact spacecraft collided with the nucleus last week. Planetary scientists studying the data collected by Deep Impact, as well as observations of the impact by other spacecraft and telescopes, said that the collision of the spacecraft's impactor probe created a plume far more opaque than expected, and containing dust with the consistency of talcum powder, rather than larger sand grains that scientists had expected. Some speculate that this means that the thermal effects of multiple passages close to the Sun by the comet may have affected the nucleus to depths far deeper than previously thought, or that the comet formed through a relatively gentle accumulation of material, rather than through high-speed collisions.

Related Links:

•  AP article
•  AFP article
•  NASA press release
•  Harvard-Smithsonian press release