Cost of building a rover that can make oxygen out of the Martian atmosphere: £1.1 billion.
Target date: 2020
Cost of building a southeast London extention to the Bakerloo line (mostly using existing track): £2.6 billion.
Target date: 2040 if we're lucky
http://www.london-se1.co.uk/news/view/7757
Can't TfL just employ a few Nasa engineers? It's not exactly rocket science...
£2.6 billion sounds like a bargain actually, when you compare it to the £15 billion cost of Crossrail (a project that was first proposed in 1974 and will open in 2018!).
Anyway, this is yet another robotic mission to Mars. I believe that the cost for a manned mission range from $30 billion to $450 billion!