More leaks continue on the President's budget proposal for FY13 to be released Monday. The Washington Post reports that the proposed planetary science budget will drop from ~$1.5B this year to $1.2B next year. (Last year's budget proposal had targeted spending for FY13 at $1.36B, so if the Post is correct, this represents a continued reduction in what was already projected to be a declining budget.) The article suggests that most of the cut would come from the Mars program, which could reduce it from ~$600M this year (projected at FY13 $441M in last years budget proposal) to something less than $300M. Based on my analysis last year, that figure would support completion of the 2013 Maven orbiter and operations of the Curiosity Mars rover. It would not support NASA's participation in the ExoMars program at levels previously discussed.
Both the Washington Post article and an analysis at the Space Politics blog report that at least some members of Congress are not happy with the proposed cuts. This creates the possibility that some or all of any cuts that are proposed may be reversed. However, the money would have to come from another program within the group of agencies funded with NASA, which includes many of the science agencies and the Veterans Administration. Those programs also have their supporters.