The ExoMars mission to Mars has been the subject of intense discussion over the last few days, as European Space Agency delegates attempt to finalise the design for the ambitious probe. At the heart of the discussion is the proposal by mission scientists to beef up the mission in order to address several worries they have. The most costly change is the request to send a combined orbiter and lander configuration, a proposal driven by several imperatives. For one thing, scientists are concerned that without an orbiter to relay data back to Earth, the ExoMars mission will be relying on American orbiting hardware for the crucial link home, and another failure such as recently befell Mars Global Surveyor would be catastrophic. Equally concerning, a recent change to the launch date from 2011 to December 2013 now means ExoMars would arrive in 2014, at a time of increased dust storm activity. Without an orbiter to wait out the storms, the lander would have to risk a perilous descent in these conditions. These changes mean a far bigger payload requiring a more powerful launch vehicle. That all adds up to substantial cost increases, and that means the member nations of the ESA will have to dig a lot deeper into their pockets to fund it. The worry is that some ESA members may decide to cut and run, threatening the entire project, which is a key plank of highly ambitious European plans to explore and eventually return material from Mars. The discussions to date appear to be veering toward acceptance of the more expensive option, but a final decision has been deferred to a later meeting on June 11th.