Spacecraft to take close-up look at comets

NASA is preparing to launch a spacecraft this week on an ambitious mission to fly close to the icy cores of at least two comets during the next four years.

If all goes well, the probe, called Contour, may resolve some of the mystery surrounding these primitive chunks of matter believed to be composed of the same material as the early solar system. It also might shed light on a long-standing question: Did incoming comets seed the early Earth with water and organic molecules, the raw materials for life?

"Comets are the building blocks of the early solar system," said Donald Yeomans, a co-investigator on the Contour science team from NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Yeomans said comets also "may well have brought much of the Earth's oceans and the Earth's atmosphere, as well as the carbon-based molecules" that serve as the building blocks of life.

Contour -- short for Comet Nucleus Tour -- is set for launch shortly before 3 a.m. Monday atop a Delta II rocket from the Cape Canaveral Air Force station in Florida. After 45 days in an elliptical orbit around Earth, the craft's onboard rocket motor will fire, sending it off toward a Nov. 12, 2003, flyby of comet Encke and a June 19, 2006, encounter with comet Schwassmann-Wachmann 3.

The spacecraft has four instruments to take pictures of the comets and measure the chemical makeup of their nuclei and the gases and dust that surround them.