"These observations give us the best glimpse yet at what's under the dusty skin of a comet," said David Harker, who led the team at the Gemini Observatory. "Within an hour of impact, the comet's glow was transformed, and we were able to detect a whole host of fine dusty silicates propelled by a sustained gas geyser from under the comet's protective crust."

Comet Tempel 1, which is seven miles across, was targeted for the Deep Impact experiment because its orbit around the sun baked its outer layer of dust into a kind of shell around a frozen core. The 820-pound NASA space probe struck it at a speed of about 23,000 mph, and data collected by the Mauna Kea telescopes showed about 1,000 tons of material were ejected from the comet in a giant cloud.

The cloud was studied by the Gemini and Subaru telescopes, and with a near-infrared, high-resolution spectrograph at the W.M. Keck Observatory. The spectrograph allows astronomers to break light down to identify the chemical makeup of dust and other particles in space. The impact revealed a mix of silicates including olivine, water and carbon-based organic compounds beneath the comet's surface. Sugita said it is likely the comet formed between the orbits of Jupiter and Neptune.

Advertiser Staff
Posted: September 21, 2005