A decision will be made at the European Space Agency's operations centre in Darmstadt, Germany, at 2.51pm Hong Kong time on whether Beagle II is ready to go. If all goes well, the drop will take place at 4.11pm.

But Beagle II still has to orbit and spin to ease into its landing path which will take about six days. It is expected to land on Christmas Day, at 10.54am Hong Kong time.

'This is make-or-break time. One estimate that space agencies usually cite is that a mission-landing success [on Mars] is about 33 per cent,' said Ng Tze-chuen, a co-designer of the Hong Kong-made drill which will collect rock samples on the planet's surface.

The pride of the European Space Agency, Mars Express, was launched on June 2 and has completed a six-month journey at an average speed of 10km a second.

It will be followed by two Nasa space probes - the twin Mars Exploration Rovers - which are scheduled to arrive next month.

Because Beagle II has no propulsion, the mother ship has been put on a collision path with the planet to release it at exactly the right moment. If Beagle II fails to eject, Mars Express will become too heavy to project on to its expected orbit and both craft will be lost.

If the Beagle II lands successfully, even if Mars Express is lost it will still be able to carry out its mission. This is because it can still transmit signals and data to Earth through Nasa's Mars Odyssey orbiter, which has been circling the planet for almost two years. The first confirmation signal of whether it has landed successfully will be transmitted through the Odyssey.

If Beagle II successfully deploys its solar panels that will power its operations, the Hong Kong-made rock drills and the German-manufactured soil-sampling moles will begin collecting rock and soil samples for geological data and signs of past or present life forms.