Deep Impact releases probe for comet collision
NASA spacecraft set for fiery impact with comet on July 4
http://www.msnbc.msn.com/id/8435968/
Updated: 10:49 a.m. ET July 3, 2005
PASADENA, Calif. - A NASA space probe was bearing down on its comet target Sunday in a mission scientists hope will end with a cataclysmic crash — and new insights into the origins of the solar system.
The 820-pound copper probe was on course to intercept the comet Tempel 1 to smash a hole in it so scientists can get their first peek at the heart of one of these icy celestial bodies.
Comets are the leftover building blocks of the solar system, which formed when a giant cloud of gas and dust collapsed to create the sun and planets. Because comets were born in the system’s outer fringes, their cores still possess some of the primordial ingredients and studying them could yield clues to how the solar system formed 4.5 billion years ago.
The “impactor” probe separated from the Deep Impact spacecraft early Sunday and began a 500,000-mile suicide dive toward the sunlit section of Tempel 1, a pickle-shaped comet half the size of Manhattan and 83 million miles away from Earth.
'Half of the hurdles are over'
Workers in the mission control room at NASA’s Jet Propulsion Laboratory in Pasadena erupted in applause shortly after the separation.
“The release went very well,” said project manager Rick Grammier. “Half of the hurdles are over.”
Meanwhile, the mothership fired its thrusters to slightly change course and stake out a front-row seat 5,000 miles from the high-speed collision, which is expected to occur at 1:52 a.m. EDT Monday.
The probe will switch to autopilot two hours before Monday’s encounter, relying on computer software and thrusters to steer itself into the path of the onrushing comet. If the probe’s maneuvers are off, the comet could miss and the mission would fail.
As Tempel 1 closes in at a relative speed of 23,000 mph, the probe should beam back unprecedented pictures of its target in near real-time until it is run over.
Glimpse inside a comet
If all goes to plan, the mothership will record the crash and resulting crater with its high-resolution telescope. About 15 minutes after impact, the craft will make its closest flyby of the comet nucleus, approaching within 310 miles. Scientists expect it will be bombarded with flying debris and will stop taking pictures, turning on its dust shields for protection.
NASA’s brigade of space-based observatories, including the Hubble Space Telescope, Chandra X-ray Observatory and Spitzer Space Telescope, also will be pointing toward the comet to record the impact. Professional astronomers from dozens of observatories in 20 countries also will observe the crash.
Little is known about comet anatomy, so it’s unclear what exactly will happen when Tempel 1 is hit. Scientists expect the collision will spray a cone-shaped plume of debris into space. The resulting crater can range anywhere from the size of a large house to a football stadium and be between two and 14 stories deep.
The probe’s anticipated impact could cause the comet to shine brighter than normal and sky-gazers may be able to see celestial fireworks with a telescope in parts of the Western United States and Latin America.
Deep Impact blasted off in January from Cape Canaveral, Fla., for its six-month, 268 million-mile journey. In what scientists say is a coincidence, the spacecraft shares the same name as the 1998 movie about a comet that hurtles toward Earth.
Discovered in 1867, Tempel 1 moves around the sun in an elliptical orbit between Mars and Jupiter every six or so years.
In April, the 1,300-pound spacecraft took its first picture of Tempel 1 from 40 million miles away, revealing what amounts to a celestial snowball. Last month, still 20 million miles away, scientists saw the solid core of Tempel 1 for the first time.
Copyright 2005 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
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