Deep Impact Throws Up New Questions

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It was the biggest Fourth of July blast ever: a 37,000-kph collision in deep space of a washing-machine-sized American spacecraft called the Deep Impact "impactor" with a comet as big as Washington. When the cosmic smash-up occurred on Monday, some 130 million kilometers from Earth, space scientists at NASA's Jet Propulsion Laboratory in Pasadena, California, and around the world leapt to their feet in rapturous applause. A spectacular crash was exactly what was supposed to happen when Deep Impact encountered Comet 9P/Tempel 1 in a search for clues to the origin of the universe.

Mankind had reached out and, for the first time, made contact — however roughly — with a comet. "The Deep Impact mission brought the world together in an excellent opportunity to make a new step in the advancement of cometary science," says David Southwood, the European Space Agency's director of science.

Along with carrying years of scientific hopes, dreams and questions, Deep Impact also took along on its mission to Tempel 1 the names — burned onto a CD — of some 625,000 people from around the world who signed up for the historic destruction under NASA's public-outreach and education program. The space agency believes that, by engaging people's imagination in space missions, which literally open new worlds before our eyes, appreciation and knowledge of the sciences are strengthened and enhanced.

Scientists have been dazzled by the impact explosion, which chief scientist Michael A'Hearn termed "spectacular" and much brighter than he had expected. "They say a picture can speak a thousand words," says project manager Rick Grammier. "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."

Over the coming weeks and months, Tempel 1 — which has an orbit running between those of Mars and Jupiter — is expected to give up some of its secrets. The $333-million U.S. mission, launched in January, was designed to create a large crater in the elongated comet — a mass of ice, rock and dust — and then to observe the crater's development, measurements and ejected matter. Scientists believe comets are among the most primitive objects in the solar system, containing beneath their surface relatively unchanged chemical and physical records from the time the system was formed some 4.6 billion years ago — clues to the primordial soup from which life on Earth eventually emerged.

The impactor was destroyed when it hit the comet but its traveling companion, Deep Impact's fly-by craft, is recording scientific data. "Soon we will begin the process of downlinking all the encounter information in one batch and hand it to the science team," says Grammier. Several other observation vehicles also recorded the deep space fireworks, including the European Space Agency's Rosetta comet-chaser. Rosetta, en route to a planned 2014 rendezvous with an even-more-distant chunk of ice, Comet 69P/Churyumov-Gerasimenko.