The European Space Agency mission ExoMars is now likely to leave Earth in 2018, a two year delay. Mission planners believed the money pledged by the European Union was insufficient to meet mission requirements, so sought help from NASA to defray some of the costs. This approach has now been approved, though budgets will still need to be reassessed before a formal full go-ahead at the end of the year. The current proposal is to use a US Atlas rocket to launch ExoMars, but the US will also lend expertise in controlling the rover's entry, descent and landing. As part of the revised plans, Europe will also look at a less costly 2016 mission, which will deliver an orbiter and a static lander. More detail can be found at the
BBC News website.