Europe has formally started the countdown clock for the launch of its Mars Express space probe, which will lift off for the Red Planet on Monday, 2 June.
By Jonathan Amos
BBC News Online science staff
The UK science minister Lord Sainsbury set a digital timepiece going at the Royal Society in London, in the presence of senior European and British space officials.
Lord Sainsbury (c) begins the Martian countdown
Mars Express, which is carrying the Beagle 2 lander, is set for an 1845 BST (2345 local time) launch from Baikonur in Kazakhstan.
The 400-million-kilometre (250 million miles) trip should see Beagle transmit its first signal from the surface of the Red Planet on Christmas Day.
The mission is Europe's first solo enterprise to another planet.
The main probe will orbit Mars and use its seven remote instruments to map the planet's surface, study its mineralogy and atmosphere, and attempt to detect the presence of water.
Beagle, which is named after Charles Darwin's famous ship, will parachute down to the surface; the touchdown impact will be softened by inflated bags.
So-called because of speed and low cost of development
Will map Martian surface and analyse atmosphere
Radar instrument can detect water several km below surface
The lander, which has cost in excess of £30m (42m euros) to put together, has a suite of instruments loaded inside its small 68-kilogram frame that will aim to detect the signature of past life - or even present-day lifeforms.
"We have the experiment on board to detect the gases given off by micro-organisms," Beagle's project leader, Professor Colin Pillinger, told BBC News Online.
"Even if those organisms are a thousand miles away, we should be able to tell if those gases are in the atmosphere."
The main spacecraft and its lander are currently being prepared at the Baikonur spaceport.
Mars Express has been fuelled and loaded atop its Soyuz-Fregat launcher.
A state commission will meet on 28 May to approve the blast-off. Assuming this happens, the rocket will then be rolled out to the launch pad on the 29th. The mission will leave Earth just a few days later.
BEAGLE 2 LANDER
Will search for signs of past and present life
Instrument "paw" can retrieve rocks and soil for examination
Carries the first microscope to travel to another planet
Europe has built the main satellite for the relatively low cost of £110m (150m euros) and if it works, the European Space Agency (Esa) hopes it can become the model for future Solar System exploration.
Already, it has been decided to use the basic design for Europe's 2005 mission to Venus.
"What is nice is that this approach costs much less than others," Esa director-general Antonio Rodota said.
"I think there will be room for other, similar missions in the future. If the scientists wish, we could use this template to explore the other planets."
But first Mars Express has to be made to work and the next few days and months will be anxious times for everyone connected with the mission.
Immediately following the launch, Mars Express will go into a one-lap orbit of Earth before its Fregat booster kicks the satellite on to a trajectory to Mars.
"The moment I'll really bite my nails is the release of Beagle," said Professor David Southwood, Esa science director. "We have to line up on a collision course with the planet, jettison this passenger and then get Mars Express the hell out there and into a safe orbit around the planet."
The separation is scheduled for 19 December. Beagle should hit the surface at 0254 GMT on 25 December. It will then deploy its solar cells and power up.
"About two hours later, the US space agency's Mars Odyssey spacecraft, already in orbit around the planet, should come over the horizon to pick up the first signal," Professor Pillinger said.
The link-up with the Americans is necessary because Mars Express will still be negotiating its way into the safe orbit.
The US has its own landing craft - two identical rovers - expected on the planet within days of Beagle, and agreement has been made for them to use Mars Express as a communication channel if necessary.
The first signal returned by Beagle will be a short tune composed by the British rock band Blur.
The first picture to come back will be a general landscape view of Mars.
A small mirror will pop up in front of one of the lander's stereo cameras to provide a 360-degree reverse-fisheye image.
"It will enable us to look all around, check the lander is OK - no bits have fallen off - and see where the air bags are," said Dr Andrew Coates, from University College London, who has worked on camera development.
"The most important thing then will be to get a stereo view of the whole area so that all the other science can get underway."
Because of the great distance between Earth and Mars, there is a lag in communications and Beagle cannot be operated in real-time.
The cameras must therefore construct a map of the landing area so that instruments on its "paw" can be guided into the correct positions alongside target rocks and soil to conduct experiments.