This will take place just before the Mars Express moves into orbit around Mars to survey its atmosphere and sends a surface probe - the Beagle II, carrying the Hong Kong equipment - to land on the planet.

'This is the most important series of manoeuvres of the entire mission. If this fails, we will lose the spacecraft, everything. The entire mission will be dead,' said Ng Tze-chuen, a co-designer of the Hong Kong-made combined drill-grinder that will be used to sample surface Martian rocks and soil.

To deliver the Beagle II to its destination, the Mars Express has been put on a collision course with the planet because the Beagle II does not have a propulsion system and has to be carried to the right drop-off point at a precise time.

After separation, the Mars Express must veer away quickly to avoid crashing into the planet. Its thrusters have to be fired at exactly the right time to move away from the collision course and at the same time, to enter into orbit around Mars to begin its own atmospheric surveying mission.

As the manoeuvres - which will start on December 19 - allow little margin for error, the European Space Agency ground control team is using real-time flight data to simulate all possible scenarios, including glitches and major systems failures on board the spacecraft and on the ground at control centre.

If it succeeds and Beagle II lands successfully around Christmas, its solar-energy-powered robotic arm will use the Hong Kong drills and grinder to gather surface geological samples.

From these samples, sensors aboard the Beagle II will be deployed to analyse their composition, including chemical signatures of past or present life forms.

'We are all holding our breath. The chances of failure are high,' Dr Ng said.