Sunday, June 12, 2005

Cosmic collision to give
Hawaii prime-time show

NASA's Deep Impact probe is set
to smash into a comet on July 3

Hawaii residents should have front-row seats for a potentially spectacular collision in space on July 3.

The show is the programmed crash of a detachable probe from NASA's Deep Impact spacecraft into Comet Tempel 1 at about 7:52 p.m.

Material ejected from deep inside the crater by the impact will give astronomers a look at what it was like when the solar system was formed 4.5 billion years ago.

"Pretty much everybody on planet Earth and all major observatories will be looking at this at the time of encounter," said Karen Meech, member of the Deep Impact Science Team with the University of Hawaii Institute for Astronomy. "I'll be surprised if there is a telescope that is not looking at it," she said in an interview.

Big Island and Maui observatories have a major role in the mission -- the first to explore a comet's interior -- as well as the Hubble and Spitzer Space Telescopes and Chandra X-Ray Observatory.

Meech, who is coordinating all ground-based and orbital satellite observatories, said at least 60 professional observatories are lined up to record the event.

NASA planned it for the best viewing time from Mauna Kea, where Meech will be with a worldwide consortium of astronomers.

An international collaboration of students and educators from the United Kingdom, Iceland and Hawaii will collect data from the Faulkes Telescope on Haleakala. The Advanced Electro-Optical System Telescope also will be observing.

Events will be held on Maui, in Hilo and Waimea on the Big Island and in Honolulu for residents who want to know more about it and participate.

The Deep Impact Spacecraft was launched from Cape Canaveral in January with a "flyby" spacecraft and a smaller "impactor" spacecraft.

They will remain connected until about 24 hours before impact when the three-foot, 820-pound copper probe is released into the comet's orbital path.

The comet is racing through space at about 23,000 mph or 6.3 miles per second, according to NASA.

It will be too faint to see without a telescope or binoculars before the impact, but will be near the star Spica and planet Jupiter, both bright objects.

"We are really threading the needle with this one," Rick Grammier, Deep Impact project manager at NASA's Jet Propulsion Laboratory in Pasadena, said in a news release. "In our quest of a great scientific payoff, we are attempting something never done before at speeds and distances that are truly out of this world."

The impact could create a crater ranging in size from a large house to something bigger than Aloha Stadium and from two to 14 stories deep, the scientists said.

But Don Yeomans, a JPL Deep Impact Mission specialist, said, "The impact would be the astronomical equivalent of a 767 jetliner running into a mosquito.

"It simply will not appreciably modify the comet's orbital path," he said, adding that the comet is not a threat to Earth.

Often called dirty snowballs, comets are composed of leftover debris from the early solar system formation, Meech said. "They preserve a record of the chemistry and physics of what was going on then."

When astronomers look at the comets, they're not really sampling the solar system because the surfaces have evolved, she said. "The goal is to look beneath the older surface layers and get at the pristine material."

Space and ground-based telescopes will observe material ejected from the comet and analyze the spectrum of reflected sunlight off of the comet to identify elements and molecules.

The comet will be much brighter because of the sunlight reflecting off the dust, Meech said.

For observers with the naked eye, the moment of impact may look like a bright new star appearing, she said, pointing out it may take some time for the dust to move away from the nucleus of the comet.

The ejected material should be brighter the next day and remain bright perhaps for a month before it fades, she said.

Astronomers have been planning the mission for about 10 years, Meech said. She has studied the comet for about eight years to learn more about its orbit, size and shape to target the spacecraft.

She said the mission is limited by cost to two or three basic instruments. The fly-by spacecraft has a high-resolution instrument with a camera and infrared spectrometer and a medium-resolution instrument. The impactor also has a medium-resolution instrument to record the craft's last moments.

Studies are expected to answer basic questions about the solar system and composition and role of comets in the Earth's early history.

All results will be aired at a scientific meeting in Brazil in early August, Meech said.

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