Europe's Space Odysseys

If all goes according to plan, Flight 158 will take off this week from Kourou in French Guiana, soaring up and away over the tiny South American country's lush equatorial forests and sandy Atlantic beaches. Flight 158 is no ordinary tourist shuttle, though. It's an Ariane-5G rocket that will launch the Rosetta spacecraft on an ambitious journey halfway across the solar system to intercept and land on Comet 67P/Churyumov-Gerasimenko, which is currently streaking across space at more than 100,000 km/h inside the orbit of Jupiter. "What's totally obsessing me is that we're launching into a comet and searching for the origins of life," says David Southwood, director of science at the European Space Agency (ESA), which is orchestrating the Rosetta project. "We're going out there, landing on a comet and doing our analysis in situ."

Southwood and his colleagues at esa are indulging their obsession at a time of heightened interest in space — and heightened controversy about space exploration. The success of ESA's Mars Express orbiter mission and NASA's Spirit and Opportunity landers — all of which sent back stunning photos of the Red Planet — promises fascinating advances in our knowledge of our planetary neighbor. But the explosion of the Columbia space shuttle last year, killing all seven astronauts on board, has raised doubts about the cost of space travel — both in terms of dollars and in human life. Unmanned missions like Rosetta — and Britain's plucky little Beagle-2, which vanished without a trace while heading to the Martian surface from Mars Express last Christmas — are safe, of course. But many wonder whether the millions, or billions, it costs to mount such expeditions wouldn't be better spent on improving life here on Earth.

So the stakes for Rosetta are high: the scientific breakthroughs have to be big enough to convince a skeptical public that the expense was worth it, and the execution of the mission has to be seamless enough to convince ESA's competitors and collaborators that Europe is in the space game to stay.

It will be at least a decade before ESA can put Rosetta to the test. The spacecraft will make a 10-year journey to Jupiter, the first time a craft has traveled, relying only on solar-cell power, beyond the asteroid belt that lies between Mars and Jupiter. Once near the giant planet, Rosetta will attempt to land on Comet 67P, one of the dirty flying snowballs that may well be the most primitive objects in the solar system. Scientists believe comets like 67P may contain chemical and physical records from the time the system was formed some 4.6 billion years ago. And since very little is actually known about the primordial soup from which life emerged, they hope the Rosetta mission will help them unlock the secrets of how it all began on Earth — or perhaps even elsewhere in the universe. Hence the name, inspired by the Rosetta Stone, the key to deciphering Egyptian hieroglyphics.

Rosetta is an ambitious and technically challenging mission. It will not be easy to keep a rendezvous in 2014 with a comet tearing through space near Jupiter. The 165-kg-payload orbiter is to chase, circle and remotely study the comet, as well as dispatch a 100-kg lander onto its surface for closer analysis. If the j1 billion mission succeeds, scientists say it will be a major step toward improving human understanding of the origin of the sun, Earth and the other planets.

In early 2014, Rosetta should be approaching the comet, having received slingshotlike "gravity assists" from flybys of Earth and Mars and then "hibernating" in deep space for 21/2 years. In August 2014, it will be mapping and characterizing the comet, using an array of scientific instruments to analyze the dust and gas spewing from the snowball's 4-km-wide nucleus. The orbiter will also release its lander, Philae, which will anchor itself to the comet in November 2014 using a harpoon and "ice screws" — drills extending from each of its three legs that rotate into the nucleus. The lander's job is to provide data on the chemical and physical properties of a selected area of the comet's surface. Rosetta is then to "escort" the comet around the sun — which 67P orbits every 63/5 years — remaining in orbit around the comet beyond the mission's nominal end in late 2015.