Europe and America sign up for Mars

Great to see that NASA and the ESA have finally inked a deal to work together on a Mars exploration program. The deal will ensure a steady fleet of probes to the red planet, beginning with a European-led orbiter in 2016, with surface rovers to follow in 2018. A network of landers has also been proposed for 2020. The ultimate goal will be to bring a sample back to Earth. I just wonder why we can't bring in some more partners? The Japanese and Chinese are building their space programs up, and so surely there would be much to be gained by creating a worldwide Mars program? More detail on the ESA/NASA deal at the BBC.