Approved by space ministers in 2005, the rover was supposed to be a fairly small venture costing no more than 650m euros. But as the project developed, it was decided the endeavour should be upgraded, to provide a bigger, more capable vehicle; and one that could carry a much broader range of science instruments.
However, the design boost also meant a huge jump in cost. The prime contractor, Thales Alenia Space, estimated the final price tag would be 1.2bn euros.
Italy, the lead nation on ExoMars, made it clear recently that it was not going to put any more cash into the mission; and with no other nations offering to make up the large shortfall in the budget, a delay became inevitable.
Because Red Planet missions are only launched when Earth and Mars are favourably aligned, the November 2013 departure must now slip to a January or February 2016 opportunity.
It is down to Europe's space ministers to take the final decision on ExoMars' future. They will meet in The Hague at the end of November to set out Europe's space policy.
The ministers will be told by officials that options will be sought to reduce the financial impact of ExoMars. One possibility is to ask the Russians and the US to take a greater stake in the mission. The US, for example, is already funding the development of two instruments.
The slight concern here is that the Americans have budget woes in their own Mars programme, with their next rover - the Mars Science Laboratory - also heading way over budget.
The decision to delay ExoMars will come as a bitter blow to Europe's scientists. It is the biggest, most expensive robotic mission in the current timeline; and is the flagship venture of Esa's Aurora programme, its roadmap to explore the Solar System.
But Professor Andrew Coates, of UCL's Mullard Space Science Laboratory, UK, urged people to stay upbeat.
"It's disappointing to be going to Mars later rather than sooner," the leader of the ExoMars PanCam team told BBC News.
"Our team are very busy building hardware and writing documents. But it seems the only way of launching early would be to dramatically de-scope the mission, which would limit the science objectives.
"ExoMars is going to the heart of one of the most significant questions for mankind - it's all about looking for past or present life beyond Earth, and that has to be done properly. The excitement of this mission will be worth the wait."
In one sense, scientists and engineers will at least be pleased that the need for a larger mission has been recognised. And for those Esa member states that are very keen on ExoMars but are troubled by the high cost, such the UK, the delay gives them more time to sort their financing.
Europe's only attempt to date to land on Mars, the Beagle 2 robot, was lost on entry to the Martian atmosphere in 2003. Europe's Mars Express satellite, which carried Beagle 2 to the planet, continues to return exceptional pictures and other remote-sensing data.
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