Rosetta's name recalls the efforts by French linguist Jean-François Champollion, who studied the etched translations on the Rosetta Stone and helped to unlock the meaning of ancient Egyptian hieroglyphs for modern archaeologists.
"Comets are thought to have provided the waters on Earth and the organics, said Alan Stern with the Southwest Research Institute of Boulder, Colo., and a collaborator on the European-led mission. "We're all made from comet stuff -- that's the going paradigm and whether it's right or wrong we'll determine by making a series of studies of comets."
Rosetta's journey will be long and arduous. Scheduled to be hoisted into orbit aboard a heavy-lift Ariane 5 rocket in mid-January, the three-ton spacecraft will fly first to Mars and then back to Earth, using gravitational momentum from the planets to slingshot itself farther into space. After close encounter with asteroid Otawara in 2006, another swing around Earth and a quick look at asteroid Siwa in 2008, Rosetta will reach its final destination: Comet Wirtanen, a celestial snowball less than three-quarters of a mile in diameter that contains leftovers from the creation of the solar system.
"It's material from an almost perfect morgue," said Stern.
The primordial sample will not be an easy catch. By the time Rosetta catches up with Wirtanen, in November 2011, it will be nearly as far away from the sun as Jupiter and barreling toward the inner solar system at about 84,000 mph, or 23 miles per second.
After braking to put itself into orbit, Rosetta will spend two years mapping the comet's surface and using a sophisticated array of remote sensing tools to analyze dust and vapors. For its closing act, Rosetta will hover about a half-mile above the comet and release a lander. As to what it might find, scientists said they have no idea what to expect.
"No one has ever tried to land on a comet before," said project scientist Gerhard Schwehm. "We don't know anything about how rough the surface is. It could be covered with fluffy snow like the Alps or it could be rocks and craters."
One thing is certain, he added, "that it will not be smooth and flat like a parking lot."
The lander is designed to stay upright on a slope of up to about 30 degrees. Upon touchdown, a harpoon will be fired to anchor the probe and keep it from bouncing -- gravity on the comet is practically nonexistent. The lander's legs then will screw themselves down into the surface to secure the craft in place.
After that, Rosetta's science team will be working fast. With about 60 hours of battery power and an unknown amount of solar power, the lander will work through a series of experiments to learn about the comet's composition, including experiments that might help determine if comets did indeed seed life on Earth.
"We're really just little babies crawling around with no real views of the world," said Stern. "Anything we learn will take us a long way."