There are two possibilities for liftoff, at 0717 GMT on Tuesday or at 0737 GMT, ESA's press office said.

   

The launch, from ESA's base in Kourou, French Guiana, was initially programmed for last Thursday, but was delayed by high-altitude winds.

  

A second attempt, on Friday, was postponed after a piece of foam insulation broke away from the fuel tank of the Ariane 5 launcher.

  

Launch operators Arianespace said the foam problem had been fixed and an "overall inspection" of the tank's insulating tiles had been carried out.

 

Enigmatic phenomena

  

Rosetta is designed to rendezvous with a comet in deep space and escort it on its path around the Sun in an attempt to uncover the secrets of one of the most enigmatic phenomena in the Solar System.

  

Its five-billion-km trek will require four planetary flybys of Earth and Mars to build up sufficient speed to meet comet Churyumov-Gerasimenko 675 million kilometres from the Sun, 10 years from now.

  

Laden with remote sensors to map the comet's surface, Rosetta will then follow the comet as it orbits around the Sun and then drop a small miniature laboratory onto its surface to carry out chemical and geological analysis.

  

Astrophysicists believe comets are primitive material left over from the formation of the planets and may contain complex, volatile molecules.

  

These could have "seeded" the infant Earth with the building blocks for DNA, according to one theory.