In November, the European Space Agency spacecraft Rosetta will lower its 100-kilogram lander Philae onto the surface of Comet-67P at a site known simply as "J".

Warwick Holmes, an Australian avionics engineer who helped build Rosetta, said the location, on the smaller "head" of the icy mass, was selected out of five preliminary sites chosen in late August.

"Landing site J was voted as the favourite site by the majority of Rosetta scientists," he said.

"It has the best combination of sun illumination, radio coverage to Rosetta, interesting science targets and has the minimum area of surface slopes greater than 30 degrees."

A backup landing site on the main body of the comet, known as "C", was also announced.

The Philae lander manager, Stephan Ulamec from the DLR German Aerospace Centre, said the unusual shape of the 4-kilometre-wide comet made choosing the site a difficult task.

"As we have seen from recent close-up images, the comet is a beautiful but dramatic world - it is scientifically exciting, but its shape makes it operationally challenging," he said.

The comet's surface is covered with large boulders, cliffs and slopes.

Comet-67P has no atmosphere and very little gravity. To stop Philae bouncing off the comet as it touches down, two harpoons will fire into the surface and three screws on the lander's feet will burrow into the ice to anchor it to the ground.

On board the lander are nine scientific instruments, which will analyse gases, measure thermal properties of the comet's surface, collect samples from the surface and take detailed pictures.

The mission arrived near the comet in August after a decade-long journey, travelling more than 6 billion kilometres.

"Rosetta is currently in the Global Mapping Phase of the mission, and is only 30km above Comet-67P's surface and shall be reduced to 20km in the following weeks," Mr Holmes said.

The craft's on-board science instruments have been busy collecting information about the comet and its emissions.

The emission of water vapour from the comet has increased by 400 per cent from the first measurements taken three months ago. This is expected as Comet-67P slowly warms up as it approaches the sun.

Other instruments have measured Comet-67P's density to be a third of the density of water.

But Mr Holmes said the most surprising discovery so far had been the absence of water ice on the comet's surface.

"The 'atmosphere' around Comet-67P is rich in hydrogen, oxygen and water vapour, so water is hidden somewhere," he said.