Britain's infamous "Beagle 2" spacecraft has been found on Mars -- 11 years after it went missing searching for extraterrestrial life.

Britain's infamous "Beagle 2" spacecraft, once dubbed "a heroic failure" by the nation's Astronomer Royal, has been found on Mars -- 11 years after it went missing searching for extraterrestrial life.

Beagle 2, part of the European Space Agency's Mars Express mission, had been due to land on Mars on Christmas Day 2003, but went missing on December 19, 2003. Until now, nothing had been heard from it since then.

But in an announcement made to a packed news conference at London's Royal Society scientific institution on Friday, space experts said the tiny Mars lander has been found on the surface of the red planet.

"Beagle 2 is no longer lost," said David Parker, chief executive of the UK Space Agency. He said scientists now had "good evidence" that the spacecraft successfully landed on Mars on the date it was due -- December 25, 2003 -- but had only partially deployed.

"This find shows that the entry, descent and landing sequence for Beagle 2 worked and the lander did successfully touch down on Mars on Christmas Day 2003," the UK space agency said in a statement.

Beagle 2 -- which measures less than 2 metres across -- was named after the ship Charles Darwin sailed when he formulated his theory of evolution. It was built by British scientists for about 50 million pounds ($85 million).

The plan was for it to report back from the Mars' surface using instruments designed to help search for signs of life, but nothing was heard after it was dropped off to make its landing.

"We were left with a mystery, a mystery that has continued to this day," Parker told Friday's news conference.

Martin Rees, Britain's Astronomer Royal, last year praised Beagle 2 and its eccentric creator Colin Pillinge, who had died at the age of 70.

"This was a failure, but a heroic failure," Rees said.

Experts say part of Beagle 2's legacy is its miniaturised technology, some of which is being provided for the ExoMars 2018 rover and being proposed for other future space missions.