NASA's top science official, Alan Stern, abruptly resigned his post yesterday as associate administrator for the Science Mission Directorate. The announcement came two days after NASA Administrator Michael Griffin overturned a directorate budget adjustment that might have meant shutting down one of the twin rovers currently operating on Mars.
Stern had held the post just shy of a year but was credited with working to expand the agency's scientific program despite flat budgets and an increasing focus on manned missions. He pushed for unmanned projects to return a sample from Mars as well as to study the solar system's outer planets up close.
"His departure is a shock to people," says researcher Mark Sykes, director of the Planetary Science Institute in Tucson, Ariz. "It means potentially a black day for science at NASA."
Stern, 50, is a planetary scientist who had previously worked as executive director of the Space Science and Engineering Division at Southwest Research Institute in Boulder, Colorado. His resignation was quickly followed by that of NASA's chief scientist, the Nobel laureate physicist John Mather.
NASA announced that Edward J. Weiler, director of the NASA Goddard Space Flight Center in Greenbelt, Md., will serve as interim associate administrator. Weiler served from 1998 to 2004 as the associate administrator for NASA's Space Science Enterprise, which during that time was merged with the Earth Science Enterprise to form the Science Mission Directorate.

Sykes speculates that Stern's resignation stemmed from cost overruns in the already tight Mars budget, specifically in the Mars Science Laboratory (MSL) project, set to launch in fall 2009 to replace the twin Mars Exploration Rovers Spirit and Opportunity, which landed on Mars in 2004. A NASA memo released in September noted that as of last summer MSL had exceeded its $1.57 billion budget by an estimated $75 million.

Last week, the science directorate notified NASA's Jet Propulsion Laboratory in Pasadena, Calif., that it would have to shave $4 million from the rovers' $20-million 2008 budget and $8 million from their 2009 budget, also $20 million. Rover project scientists announced late Monday that to do so, they would have to place Spirit in hibernation mode and limit operations with Opportunity. Griffin immediately rejected the proposed cuts, which NASA said were not cleared with him first.
"I think [Stern] was trying to keep Mars overruns within the Mars program," Sykes says. The former associate administrator was known for a no-nonsense attitude that "ruffle[d] some feathers," he adds. "People would come to him with requests for additional money after cost overruns [in past missions] … and his response was, 'No.' People weren't used to hearing that."
Observers can only guess whether Stern stepped down voluntarily, but the proposed cuts to the rover budget met with "a lot of resistance in the Mars community," says James Bell of Cornell University, a lead scientist on the Mars rover mission. "It's clear that [Stern] was pushing very hard on the system," he says. "He may have thought he had more latitude with Mike Griffin than he did."

In a prepared statement, Griffin said that Stern had "rendered invaluable service to NASA as the principal investigator for the Pluto New Horizons mission, as a member of the NASA Advisory Council, and as the associate administrator of the Science Mission Directorate.  While I deeply regret his decision to leave NASA, I understand his reasons for doing so, and wish him all the best in his future endeavors."
The statement did not specify Stern's accomplishments, and a NASA spokesman said Stern was not granting interviews yet but would likely do so in the near future. In a short e-mail from Stern, circulated to colleagues the day he left and forwarded by NASA, he said that he had tendered and Griffin had "reluctantly accepted'' his resignation. He added that Griffin "remains, in my eyes, the best Administrator NASA has ever had."
Sykes said that although Stern did not always give researchers what they wanted, scientists respected him for his scientific credentials and experience. "Stern understood the value of the science that's done in the Science Mission Directorate and understands what's necessary to actually make that happen."
"People are just stunned," Sykes said. "They're just flat stunned."