European scientists say the British-built Beagle 2 probe has successfully separated from its mother ship, a critical step in its journey toward a Christmas Day landing on Mars.

The space experts say they are relieved and excited after the Mars Express orbiter sprung the Beagle 2 free for its rendezvous with the Red Planet.

The separation was triggered by 115 commands sent across 250-million kilometers of space to the unmanned orbiter from the European Space Agency mission control center in Darmstadt, Germany.

Beagle 2 is the brainchild of British scientist Colin Pillinger, who sees the mission as a historic opportunity.

"This was definitely a case of seize the moment," he explained, "because Mars is closer to Earth than it has been ever in the last 60,000 years and this was the one opportunity when Europe was going to launch a spacecraft to Mars and far be it for me to find myself in a position years from now and to say, 'I missed it.'"

If all goes as planned, Beagle 2 will land on Mars on December 25, Christmas Day, to begin a six-month search for signs of life in a region once thought to have been a Martian sea.

This is Europe's first mission to another planet. It is being followed by two American mobile landers expected to touch down on Mars in January.