By Jonathan Amos
Science reporter, BBC News
European industry has received the formal request to cost the design and construction of a robotic rover to send to the Red Planet in 2013.
The European Space Agency has asked Thales Alenia Space to report back with a price in just over 10 weeks.
The French-Italian group will convene a meeting of its major contractors in Turin next week to discuss the project.
The industrial partners face an intense period of work to refine and test the details of the ExoMars rover concept.
Its general outline was approved by European Space Agency (Esa) delegations in June.
Known as the "enhanced baseline" design, it calls for a vehicle weighing just over 200kg that can trundle over the Martian surface to look for signs of past or present life. It will be given a 16.5kg suite of scientific instruments to carry out the survey.
"We now have a deadline of 8 October for delivery of the full committing proposal from industry," said Vincenzo Giorgio at Thales Alenia Space, the lead industrial partner on the ExoMars project.
"This is a challenge not only because there is August - normally a holiday all over Europe - but also because two months is a major challenge anyway to make a full blown proposal," he told BBC News.
Esa officials have told the member state delegations to expect ExoMars to cost in the region of one billion euros. This figure includes the construction, launch and operational phases of the mission.
The manufacturing and testing stage is likely to come out somewhere just over 50% of the total cost, and takes into account the money needed to fund a control centre in Turin, together with an exact copy of the rover and a dummy Mars landscape.
The simulator will be used by engineers to try out any unusual manoeuvres and software changes on Earth before commands are uploaded to the real rover sitting on the Red Planet.
Work is proceeding at pace to develop the improved breadboard, or prototype, versions of key components and systems.
Perhaps the most dramatic technology demonstration to date has been that of the vented, or dead-beat, airbags which will be used to cushion the vehicle's landing on the Red Planet.
These are very different from the bouncing bags employed so successfully by the US rovers on their descent to Mars. Their enveloping bags bounced more than 25 times and travelled some 200m across the dusty surface before bringing their precious cargoes to a safe and secure stop.
EXOMARS MISSION CONCEPT
Set to leave Earth in 2013; primary aim is to search for life
Will launch on a heavy-lift Proton or Ariane 5 rocket
Vented landing bags allow for a larger payload
Rover will carry a 16.5kg 'Pasteur' instrument suite
30kg geophysics/environment static station also possible
This would study the weather and listen for 'Marsquakes'
Concept to cost Esa states more than first estimates
ExoMars and its landing platform will instead come down atop squashable bags. On touching the surface, sensors will send a signal to open vents, causing a rapid but predictable deflation.
This should bring the rover-platform to an immediate stop in an upright orientation.
Five successful tests have been conducted at the Centro Italiano Ricerche Aerospaziali (Cira, Italian Aerospace Research Centre), including the first angled drop.
"We have now done a test that has reproduced a lateral vector velocity; the inclination was chosen to test the possibility of - and the reaction of the whole system to - a landing that is not vertical," explained Mr Giorgio.
"This is important because wind is one variable we have to take into account."
Other near-term breadboarding will include work by Galileo Avionica on the drill that ExoMars will use to pull soil samples from below the Martian surface. And development work on the vehicle's six-wheeled chassis - the most iconic aspect of the rover programme - is also being taken to another level.
EADS-Astrium has been furthering knowledge of the vehicle's locomotive and navigation capability using a prototype dubbed "Bridget".
This will now be superseded by two new experimental chassis which will independently investigate key design parameters.
Contracts have been placed with a Swiss-German consortium, led by Oerlikon, and Canada's MacDonald, Dettwiler and Associates.
"We learnt a lot with Bridget but there are aspects of the configuration that need to be improved," said Chris Draper from Astrium's UK-Stevenage base.
"We have experts in Canada and in a Swiss-German consortium who are both going to carry out trade-offs of different concepts. They will then breadboard the most promising (they will build two more Bridgets, essentially) which we can test to be sure we have the best configuration."
The outcome of Esa's Request For Quotation (RFQ) - the rover mission's manufacturing price tag - will be discussed by delegations in November.
Assuming they are happy and work proceeds, a Preliminary Design Review (PDR) is planned for the first quarter of 2008. This will freeze the design of the mission.
Beyond this date, changes cannot be made to the concept without seriously jeopardising the scheduled launch date of 2013.