Quotes of the Day

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.

ESA Venus Express

In carrying out its tasks, Rosetta will hopefully help scientists find out if comets may have acted like cosmic Johnny Appleseeds, scattering the building blocks of life on their interstellar travels. Because 67P's gravity is only a minuscule fraction of Earth's, the Rosetta orbiter will be able to observe from just 2 km away. Its state-of-the-art instruments — some of which were funded by NASA — should provide invaluable data on the comet's temperature, gases and charged atmospheric particles. Scientists are especially interested in learning how the comet changes as it moves closer to the warmth of the sun from the vast frozen reaches of the solar system. Success in such a complex mission, where there is no room for error, would surely capture the public imagination a decade hence, and encourage scientists to pursue other daring endeavors.

As if Rosetta weren't enough, ESA craft are scheduled to make a number of other stops throughout the solar system over the next few years. The Cassini/Huygens project will take a joint NASA-ESA craft to Saturn in the summer and to Titan, Saturn's largest moon, next year. "Titan is the only moon in the solar system with an atmosphere," Southwood says. "A trip to Titan is like a trip to early Earth, like Earth's atmosphere without the oxygen." Then there's Venus Express, modeled on Mars Express, which will investigate the planet's super-hot surface and thick, heavy atmosphere, which is 96% carbon dioxide. Says Southwood: "We're not expecting to find life, but to try to answer the question, 'Why is Venus such a deadly place?'" Europe is also moving ahead with the Columbus science laboratory, its biggest single contribution to the International Space Station, and further down the road are projects for the advanced study of gravitational waves and cosmic microwave background radiation.

But the granddaddy of all space missions is Aurora. Now in an initial three-year preparatory stage, Aurora is laying the groundwork for the next steps in the human exploration of space. With a European human landing on Mars in 30 years as Aurora's ultimate goal, EADS Space Transportation, a Bremen-headquartered firm that makes space vehicles and components, is in the initial stages of exploring a Mars Sample Return mission, which would land a craft on Mars and return a small capsule with Martian surface samples to Earth.

Because the technology and expense of such adventures are so daunting, esa varies its partners on a mission-by-mission basis. ESA has a longstanding cooperation with NASA and a good working relationship with Russia, which sent Mars Express and Beagle-2 aloft from its Baikonour site in Kazakhstan. The suspension of shuttle flights after the Columbia disaster means that ESA must now rely on Russia's Soyuz vehicles for flights to the International Space Station. And ESA has just agreed to build a Soyuz launchpad at its Kourou facility by 2006. China and Japan are also expected to play larger roles in space in the years ahead. Japan, which in December abandoned its troubled Nozomi mission to Mars — its first interplanetary effort — is said to be interested in launching a revised Beagle mission. China is expected to carry out its second manned mission, Shenzou 6, sometime this year.

Europe, of course, has less money to work with than the U.S. — ESA's budget is about one-sixth of NASA's, amounting to roughly €2.7 billion. And much of ESA's money goes into projects with terrestrial applications, like telecommunications and weather satellites. But, says Southwood, European countries need to commit funds for exploration too. "They have to recognize that to do serious things in space does not break the bank for rich countries," he says. While space exploration costs Americans about $50 a year, per capita, the European average is about $15, scientists commented at a recent Aurora meeting in London. Contrasting the potential additional cost of Aurora with the money spent annually in Europe on personal grooming products — €7.7 billion in 2002 — Richard Wade, director of programs for Britain's Particle Physics and Astronomy Research Council, said: "Europe is itching to go to Mars, so we either buy some ointment or go there."

Southwood has a different metaphor. "A society needs this, like it needs art galleries. Of course, you wouldn't want to spend your whole gross national product on art galleries, but if you didn't do any spending on them, you'd be in a desert." Kind of like Mars, but less nourishing for the spirit of discovery.

• MARYANN BIRD
• Europe's space agency goes in search of the origins of life