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NASA's Deep Impact Mission Succeeds in Comet Collision

05 July 2005

Impact beneath comet's surface may yield clues to solar system's formation

Washington -- After 172 days and 268 million miles of deep space travel, NASA’s unmanned craft Deep Impact crashed into comet Tempel 1. The collision between the coffee-table-sized impactor and city-sized comet occurred July 4.

The high-speed destruction of NASA's Deep Impact probe generated a large flash that provided an excellent light source for the two cameras on the Deep Impact mothership, which was flying about 500 kilometers below the comet.

Deep Impact scientists believe the 372-kilogram impactor vaporized deep below the comet's surface when the two collided at a speed of about 10 kilometers per second. The potato-shaped comet is 14 kilometers wide and 4 kilometers long.

Official word came five minutes after the impact when the spacecraft's medium-resolution camera sent an image to the computer screens of the mission's science team and showed the telltale signs of a high-speed impact.

"They say a picture can speak a thousand words," said Deep Impact project manager Rick Grammier of NASA's Jet Propulsion Laboratory in California. "But when you take a look at some of the ones we captured in the early morning hours of July 4, 2005, I think you can write a whole encyclopedia."

According to NASA, the $333 million Deep Impact mission provides a glimpse beneath the surface of a comet, where material from the solar system's formation 4.5 billion years ago is thought to be relatively unchanged.

Mission scientists expect the project will answer basic questions about the formation of the solar system by offering a better look at the nature and composition of the frozen celestial travelers known as comets.

The flash created by the impact was just one of the visual surprises for the Deep Impact team. Preliminary assessment of the images and data sent from the flyby spacecraft has offered a glimpse into the life of a comet more detailed than any previously seen.

At a news conference held later on July 4, Deep Impact team members showed a movie depicting the final moments of the impactor's life. The final image from the impactor was transmitted from the short-lived probe three seconds before it met its fiery end.

"The final image was taken from a distance of about 30 kilometers from the comet's surface," said Deep Impact principal investigator Michael A'Hearn of the University of Maryland.

"From that close distance we can resolve features on the surface that are less than four meters across,” he added. “When I signed on for this mission I wanted to get a close-up look at a comet, but this is ridiculous … in a great way."

At the moment the impactor was vaporizing in its 10-kilometer-a-second collision with comet Tempel 1, the Deep Impact flyby spacecraft was monitoring events from nearby, and will continue to do so for several days.

"The flyby surviving closest approach and shield mode has put the cap on an outstanding day," said Grammier. "Soon, we will begin the process of sending all the encounter information in one batch and hand it to the science team."

More information about Deep Impact is available on NASA’s Web site.

The Tempel 1 collision was one of world’s largest astronomical observation campaigns. Many other space- and Earth-based observatories documented the effects of the spectacular collision, including NASA's Hubble Space Telescope and the European Space Agency’s (ESA) Optical Ground Station and Rosetta spacecraft.

Hubble astronomers noticed that the inner cloud of dust and gas surrounding the comet's nucleus increased by about 200 kilometers in size following the impact The impact caused a brilliant flash of light and a constant increase in the brightness of the inner cloud of dust and gas.

Hubble's Advanced Camera for Surveys' High Resolution Camera took visible-light images of the comet before and after the impact.

The Hubble telescope continued to monitor the comet, snapping a third image in the sequence 62 minutes after the encounter.

In that photo, the gas and dust ejected during the impact are expanding outward in the shape of a fan. The fan-shaped debris is traveling at about 1,800 kilometers per hour, or twice as fast as the speed of a commercial jet. The debris extends about 1,800 kilometers from the nucleus.

A sequence of Hubble images, including video images are available the telescope’s Web site.

The 1-meter European Space Agency (ESA) Optical Ground Station (OGS) telescope at the Observatorio del Teide on Tenerife, Canary Islands, also captured images of Tempel 1’s dust and gas.  Images from the OGS telescope are available on the ESA’s Web site.

Images taken by the OSIRIS Narrow Angle Camera on board ESA's Rosetta spacecraft show how the brightness of Tempel 1 developed after impact.  Images from the Rosetta spacecraft are also available on ESA’s Web site.

Rosetta, launched in March 2004 and on its way to Comet 67P/Churyumov-Gerasimenko, is expected to approach the comet in early 2014 and be the first mission ever to orbit and land on a comet.  From May 2014, Rosetta will study the nucleus of the comet and its environment in detail for nearly two years and land a probe on its surface.

(Distributed by the Bureau of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)