Particles tossed up by NASA's Deep Impact strike on a comet in July consist largely of olivine — green silicate crystals commonly found in volcanic material in Hawai'i.

The dust cloud that resulted when the NASA probe struck Comet 9P/Tempel 1 on July 4 was studied by telescopes on Mauna Kea, which measured how much dust was thrown up and what it is made of. Scientists said the dust is similar to the particles found on Hawai'i's green sand beaches but much smaller.

Comets contain material from a time near the formation of the solar system 4.6 billion years ago, and study of the dust provides researchers with a glimpse of the basic materials that formed the planets.

The results of the Mauna Kea observations of the Deep Impact experiment are highlighted this week in the journal Science.

"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.

Seiji Sugita of the University of Tokyo, a Subaru telescope team member, said the amount of material that was thrown up shows the comet has a "relatively soft consistency." Other scientists have said gravity holds the dust and other materials together in a clump that is about as firm as a snowbank.

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.