Rosetta, as the unmanned probe is called, is designed to land on the comet -- a first in space exploration -- and spend the following 18 months gathering data about these enigmatic wanderers of the solar system.

The European Space Agency (ESA) was due to launch it on January 12 from Kourou, French Guiana, using a standard Ariane 5 launcher.

But the launch will now be postponed by "several days" to let experts complete an investigation into the loss of the beefed-up version of the Ariane 5 on its maiden trip.

"A new launch date will be announced... on Saturday, January 11," Arianespace, which markets ESA's Ariane launchers, said in a statement from its Paris headquarters.

Rosetta is destined to loop around Mars, using the Red Planet's gravitational pull as a slingshot to propel it to a rendezvous with the comet Wirtanen in 2011.

The alignment of Mars and Earth means that the mission has a launch window of just 19 days, and cannot be delayed beyond that.

The Ariane-5ESCA, a version of the Ariane 5 that is designed to carry a 10-tonne payload and is to be used to launch Rosetta, had to be blown up after it veered off course shortly after launch on December 11.

It carried Hotbird TM7, a TV satellite built for Eutelsat, and Stentor, an experimental communications satellite built for the French space institute CNES. The two satellites, together worth several hundred million dollars, were also lost.

Initial inquiries point to problems with the main-stage engine, the Vulcain-2, which is one of several major modifications from the standard Ariane 5.

However, the beefed-up and standard versions of the Ariane 5 share many components, and experts are eager to check whether there is any flaw that is common to both designs.

ESA set up an independent panel to probe the failure, which is due to report back on January 6. That deadline has not changed, but the work means "irreversible operations linked to Rosetta's launch have been suspended," the Arianespace statement said.

SPACE.WIRE