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NASA's Deep Impact Spacecraft Blasts Off

NASA's Deep Impact Spacecraft Blasts Off on Its Comet-Smashing Mission

In this photo released by NASA a Delta II rocket carrying the Deep Impact spacecraft lifts off from the Cape Canaveral, Fla. Air Force Station Wednesday, Jan. 12, 2005. Scientists are counting on Deep Impact to carve out July 4 a crater ranging in size anywhere from two to 14 stories deep, and perhaps 300 feet in diameter in Comet Tempel 1. It will be humanity's first look into the heart of a comet, a celestial snowball still preserving the original building blocks of the sun and the planets.(AP Photo/NASA,Scott Andrews)

The Associated PressThe Associated Press

CAPE CANAVERAL, Fla. Jan 13, 2005 — NASA's Deep Impact spacecraft has begun its one-way trip to a fiery confrontation in space a journey hopefully worthy of its Hollywood name.

The craft blasted off Wednesday on a six-month mission to smash a hole in a comet and give scientists a glimpse of the frozen primordial ingredients of the solar system.

"We are on our way," said an excited Michael A'Hearn of the University of Maryland, the mission's chief scientist. Minutes later, the spacecraft shot out of Earth's orbit and onto its collision course.

Scientists are counting on Deep Impact to carve out a crater in Comet Tempel 1 that could almost swallow the Roman Coliseum. It will be humans' first look into the heart of a comet, a celestial snowball still containing the original building blocks of the sun and the planets.

Because of the relative speed of the two objects at the moment of impact 23,000 mph no explosives are needed for the job. The force of the smashup set for the Fourth of July will be equivalent to 4 1/2 tons of TNT, creating a flash that just might be visible in the dark sky by the naked eye like a spectacular fireworks display.

The flight was barely under way when an overheating problem was detected by the spacecraft itself. Onboard computer software put Deep Impact in a protective "sleep" mode that flight controllers expected to emerge from within 24 hours, via recovery commands.

"We don't see it as a long-term threat by any means," said project manager Richard Grammier. The spacecraft is healthy, with the solar panel deployed and generating power, and the temperature increase in the propulsion-system heaters is slight and well within safety limits, he said.

"We'll be there July Fourth," NASA launch director Omar Baez said.

Deep Impact is carrying the most powerful telescope ever sent into deep space. It will remain with the mother ship when the copper-fortified impactor springs free the day before the comet strike, and will observe the event from a safe 300 miles away.

NASA space telescopes like the Hubble will also watch the collision, along with ground observatories and amateur astronomers. The impactor will have a camera, too, that will snap pictures virtually all the way in.

Nothing like this has ever been attempted before.

Little is known about Comet Tempel 1, other than that it is an icy, rocky body about nine miles long and three miles wide. Scientists do not even know whether the crust will be as hard as concrete or as flimsy as corn flakes.

"One of the scary things is that we won't actually know the shape and what it looks like until after we do the encounter," said Jay Melosh, a planetary geologist at the University of Arizona.

The comet will be more than 80 million miles from Earth when the collision takes place on the sunlit side of the comet, NASA hopes, in order to ensure good viewing by spacecraft cameras and observatories. The resulting crater is expected to be two to 14 stories deep, and perhaps 300 feet in diameter.

Scientists stress that Deep Impact will barely alter the comet's orbital path around the sun and will not put either the comet or a chunk of it on a collision course with Earth. In the 1998 movie "Deep Impact," astronauts try to blow up a comet in hopes of saving the Earth, but the comet winds up being split in two and one section slams into the Atlantic, creating a huge tsunami on the East Coast.

A jagged, cratered comet like the one headed for Earth in the movie would be difficult if not impossible to hit because of all the shadows, Melosh said. Comet Tempel 1 is believed to be smoother and easier to strike, unlike that "Hollywood nightmare."

The scientists came up with the Deep Impact name independently of the movie studio, around the same time, neither knowing the other was choosing it, even though some members of NASA's Deep Impact team were consultants on the picture.

The entire mission costs $330 million.

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