EDIT: The Planetary Society has issued a statement.
surprising and sad development at NASA Headquarters this morning: Alan Stern has resigned as the Associate Administrator for the Science Mission Directorate at NASA. I don't know any details but the timing strongly suggests it has to do with the kerfuffle about Mars program funding. I have the utmost respect for Alan's efforts at Headquarters to hold the line on budgets and to initiate a great many improvements and inject new energy into programs, from Research and Analysis to the Discovery program to outer planets flagship missions and Mars Sample Return. Alan was a true scientist leading scientific exploration of the solar system, and has more energy than any five other people. I think his departure represents a great loss for American planetary exploration. There will undoubtedly be more said about this later. NASA announced that Alan's temporary replacement is Ed Weiler.