NASA has launched a comet-chasing satellite on a mission to get within 60 miles (100 km) of a comet nucleus to study frozen samples of the solar system from its infancy. Scientists hope it will provide important evidence on the evolution of the solar system and particularly the formation of the planets.
The satellite, named Contour, for Comet Nucleus Tour, was launched aboard a Boeing Delta 2 rocket from the Cape Canaveral Air Force Station in Florida early yesterday.
NASA reported the satellite was in its proper orbit and working well after launch. It will orbit the Earth until August 15th, when onboard rockets will send it towards an encounter with Comet Enke in 2003, then Comet Schwassman-Wachman 3 in 2006.
Contour is equipped with a debris shield so it can navigate closer to the comets and survive bombardment from the minute particles of dust and frozen water that form a comet's most distinctive feature, the tail.
The shield includes a layer of Kevlar, the material used in bullet-proof vests, to help vaporise particles striking Contour with the force of .22-calibre bullets.
Contour will spend most of its operational life in hibernation mode, NASA said, to hold down costs on the $158 million programme.
During each of its near-comet passes, its four science instruments will work for about six minutes, collecting hundreds of photographs and about two gigabytes of data.
Comets are common in the solar system - there may be trillions altogether, experts say - but most remain far beyond the orbit of Pluto, the outermost planet, and beyond the reach of scientists.
However, scientists remain interested because they believe each has a nucleus frozen some 4.6 billion years ago, at the time planets were forming, and may contain vital secrets.
Numerous theories, from the destruction of dinosaurs to the beginning of life on Earth, involve comets
"Comets are the solar system's smallest bodies, but among its biggest mysteries," said Mr Joseph Veverka of Cornell University, Contour's principal investigator. "We believe they hold the most primitive materials in the solar system and that they played a role in shaping some of the planets, but we really have more ideas about comets than facts."
Contour's science teams hope there will be less mystery and more knowledge after their spacecraft encounters its comet targets.
"I'd expect to find that the ideas and the theories we have right now will be somewhat off-base," said project scientist Mr Michael Belton, an astronomer with the Kit Peak Observatory. "I think we have a fair chance of overturning the current paradigm and replacing it with honest truth."
Enke was chosen as a target because it has been studied in some detail and could provide a frame of reference for the new data.
The father of comet science, Mr Fred Whipple, used Enke some 50 years ago to develop his "dirty snowball" model for comets. At 95, Mr Whipple is a project scientist on Contour.
Schwassman-Wachman 3 was of less interest to scientists until the mid-1999s, when it split into three parts. Scientists expect to find large portions of the nucleus exposed to Contour's instruments.
Contour will return to Earth orbit after studying the two comets and can be sent out again if a good opportunity presents itself.