The document mentions the possibility of pushing MSL back to 2011 instead of 2009, and thus the possibility of a scout-class mission instead that year -- except that it's awfully late to put together a mission design, they say.

Well, we have a rover design that seems to work pretty darn well -- why not send another MER for a 2009 mission? That seems like an obvious idea to many people here, but reading that document you get the sense it didn't even ocurr to them.

Two questions to which I don't know answers:

1. Would building and launching an MER clone -- no design changes, just build a copy -- fit within the scout-class budget?

2. Did MER depend on the favorable opposition in 2003? It's certainly possible that the 2009 geometry would cause an MER repeat to crash into a constraint -- too heavy, entry velocity too high, whatever. That is an important point that those of us saying "send more rovers!" have glossed over; how much difference it makes I leave to our rocket scientists...