The unmanned spacecraft Rosetta was to have been launched in January on a 10-year mission to chase the comet Wirtanen and send a lander to analyse its surface, a first in the history of space exploration.

But the launch was scrapped as ESA carried out a reliability check of its Ariane-5 rocket following the disastrous failure of a heavy version of this vehicle the previous month.

Because of that, Wirtanen was scrapped as the project goal, and Rosetta was placed in storage while scientists assessed other cometary targets.

The new goal is the comet Churyumov-Gerasimenko, ESA said in a press statement. Rendezous is expected in November 2014.

Approval for the reconfigured mission was given on Tuesday by ESA ministers, it said.

Comets are believed to consist of virgin material left over by the creation of the Solar System billions of years ago.

Understanding their chemical composition will also, it is hoped, shed light on how Earth and the other planets were created and evolved.

SPACE.WIRE