PARIS, Feb 5: The countdown to the launch this month of Rosetta, a billion-dollar comet-chasing spacecraft, is proceeding on schedule, the European Space Agency (ESA) said here Thursday.

Rosetta is due to be launched on Feb 26 from ESA's space base in Kourou, French Guiana, on a 10-year mission to chase the comet Churyumov-Gerasimenko and land a laboratory probe on its surface.

"This mission is almost science fiction," Marcello Coradini, responsible for Solar Systems programmes at ESA, told a press conference.

The launch window closes on March 17, after which the only other possibility would be in January 2005, possibly using a Russian Proton rocket, he added.

The mission is the longest and most ambitious deep-space mission ever attempted by Europe.

Scientists believe comets are virtually pristine material left over the creation of the Universe.

Some suspect that comets harbour complex carbon molecules that may have seeded Earth with the chemical building blocks for making life when the planet was bombarded by space rocks in its infancy.

"The Rosetta mission has a potential for making spectacular discoveries about the origin of the world and, perhaps, about the origin of life itself," French astrophysicist Jean-Pierre Bibring said. -AFP