Pioneering scientist Professor Colin Pillinger has died, the agency that represents him said.
The planetary scientist, who was the driving force behind Britain's Mars lander Beagle 2, suffered a brain haemorrhage at his home in Cambridge.
The professor, who was awarded the CBE in 2003, later died in hospital.
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Prof Pillinger's family said his death was "devastating and unbelievable".
He became a professor in interplanetary science at the Open University in 1991, and earned a host of other qualifications during his prestigious career along with numerous awards.
He was most famous for the ill-fated Beagle 2 mission to Mars, which was supposed to land on the planet on Christmas Day 2003 and search for signs of life, but vanished without a trace.
It was last seen heading for Mars on December 19, after separating from its European Space Agency mothership Mars Express.
Afterwards Prof Pillinger spoke of his frustration at the failed probe, and said there was nothing that should not have worked.
Prof Pillinger, who died aged 70, was diagnosed with multiple sclerosis in 2005.
He said at the time that the illness would not stop his efforts to get Beagle technology back on Mars.
He began his career at Nasa, analysing samples of moon rock on the Apollo programme.
The father-of-two gained a PhD in chemistry from the University of Swansea before becoming a research fellow at Cambridge University.
Many took to Twitter to pay tribute to the professor.
Science fiction author Keith Mansfield wrote: "V sorry to hear about Prof Colin Pillinger via @spacecharlieuk. Great advocate for space & of course #Mars."
Space scientist Charles Laing tweeted: "Colin Pillinger was a true visionary, accomplished scientist & inspiration to those around him - sorely missed."
The European Space Agency wrote: "Shocked and saddened to learn of the death of Professor Colin Pillinger."