Scientists were crossing their fingers last night that Britain's Mars probe Beagle 2 had not ended in disaster.
The spacecraft, which has travelled 250 million miles to search for signs of life on the Red Planet, failed to make contact with Earth early yesterday.
A call-sign from the lander should have been received shortly after 6am.
But the message, in the form of a nine-note tune composed by members of the pop group Blur, never arrived.
The signal should have been relayed to Earth by the Nasa spacecraft, Mars Odyssey, that has been orbiting the planet since 2001.
Another chance to check whether the tiny craft had survived was due late last night. The scientists had to wait until the right part of Mars was pointing towards the Earth.
Then, they planned to turn the giant radio telescope at Jodrell Bank in Cheshire towards the planet.
They were hoping that the telescope will pick up a faint carrier signal, no stronger than that from a mobile phone, direct from Beagle 2's transmitter.
Unlike the relayed message, which was to contain Beagle 2's first image from Mars, the Jodrell Bank signal would include no data.
Earlier, members of the Beagle 2 team and their guests heard the frustrating news at the Open University's offices in Camden, north London.
The project's chief scientist, Professor Colin Pillinger, who led an all-night vigil at the centre, told waiting journalists: "I'm afraid it's a bit disappointing, but it's not the end of the world. Please don't go away from here believing we've lost the spacecraft."
Prof Pillinger said Beagle 2 was programmed to make at least 14 possible transmissions via Mars Odyssey.
Even if there is no contact via Mars Odyssey, there could still be a slim chance of getting the signal when Beagle 2's Mars Express mother ship starts operating in about ten days' time. Unlike Odyssey, it is designed to work hand-in-hand with the probe.
Mars Express was yesterday said to be making good progress settling into its Mars orbit. On Friday, Beagle 2 separated from Mars Express and appeared to be on a perfect course for a Christmas Day landing.
But first it had to endure a perilous descent through the Martian atmosphere, slowing from 12,500mph to 36mph in under eight minutes.
The craft's heat shield, two parachutes, and protective inflatable gas bags all had to work without a hitch.
Beagle 2, weighing less than 70kg and no bigger than a motorbike wheel, was set to be the first European spacecraft to land on another planet.
For 180 days it was to test soil, rock and air samples for signs of past or present life on Mars.
The probe may have landed in the wrong area - blown off course by Martian winds - or its antenna could be pointing the wrong way. Alternatively there may have been a communications breakdown.
Worse scenarios are that the craft burned up in the atmosphere, or the chutes or gas bags failed.
Most scientists who waited up with Prof Pillinger remained hopeful.
Open University geologist Dr Dave Rothery, who helped in the selection of the landing site, said: "Naturally I am disappointed, but it's early days. It was always on the cards that this might happen."
He said it was possible Beagle 2 had landed tilted on its side on the edge of a crater, pointing its antenna away from Odyssey.
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