— The abrupt resignation of Alan Stern after serving just one year as associate administrator of NASA’s Science Mission Directorate leaves unanswered the question of how the agency will cope with rising costs in a Mars exploration program whose budget is slated to decline over the next several years.

Mars advocates have complained in recent weeks about the spending plan, and the grousing reached fever pitch after the Science Mission Directorate sought to offset cost growth on the 2009 Mars Science Laboratory (MSL) in part by reducing funding for two small rovers now operating on the surface of the red planet.

“The current battle … this is just a skirmish,” said Philip Christensen, a Mars researcher at
and Space Exploration in
. “It’s going to be a very long war. The question is … does Mars deserve to continue to be funded and supported at the level it has been? I think we’re beautifully poised to make tremendous advances in our understanding of Mars if we continue the Mars program.”

In an interview March 26, the day Stern informed colleagues via e-mail of his impending departure, Christensen noted that NASA’s spending on Mars exploration is slated to decline by half over the next eight to nine years.

“And if that goes forward that would have a devastating effect on the Mars program. From my perspective, that’s a debate … that’s a discussion that really needs to be had out in the open,” Christensen added. “I believe that the Mars program is truly successful … one of the best things that NASA does and should continue to be supported the way it has been for the past decade.”

Congress too, has voiced displeasure with Mars exploration spending plans. During a March 5-6 hearing of the House Appropriations commerce, justice, science subcommittee, Reps. Adam Schiff (D-Calif.) and John Culberson (R-Texas) called the proposed cuts unacceptable and vowed to use their clout as appropriators to keep the program funded at current levels. The 2008 budget for the Mars Exploration Program is $555 million.

But the most recent budgetary pressure has come from within: namely, a cost overrun approaching $200 million on the MSL, a nuclear-powered rover slated to launch in 2009. To offset that overrun, the Science Mission Directorate told NASA’s Jet Propulsion Laboratory in
, to curtail spending on other Mars activities, including the Spirit and
rovers, which have been plying the martian surface since January 2004. Spending on the rovers was to be cut by about 40 percent, or $8 million per year, which would have forced NASA to put one of the robots out of action.

This directive was quickly reversed by NASA Administrator Mike Griffin, however, on grounds that it had not been properly coordinated with agency headquarters. “The NASA administrator stated that no Mars rover operations will be suspended or shut down,” the agency said in a March 25 statement. “This means that the Mars Exploration Program will not take any action as a result of the initial letter.”

Stern tendered his resignation that same day, informing colleagues early the following morning.

“I understand that it was the endpoint of a lot of frustration and a difference of professional opinion between
and Stern on how to proceed in a particular situation,” said John Logsdon, director of the Space Policy Institute at the
and an advisor to NASA.

In an e-mail to colleagues March 26, John Mather, chief scientist in the Science Mission Directorate, said Stern’s resignation was greeted with shock and a sense of loss among his staff. “In his talk to the Science Mission Directorate he said that the management issues were about cost control and that he did not see a way for him to do what needs to be done,” Mather said in his e-mail, a copy of which was obtained by Space News. “He didn’t go into details. Evidently there are extremely strong opinions about all this.”

In a March 24 telephone interview, Stern said trying to absorb the MSL overrun within the Mars Exploration Program rather than somewhere else in the science program is “just good etiquette.”

During a March 12 presentation at the Lunar and Planetary Science Conference held in
, Stern said the MSL’s total cost has grown to about $2 billion.

“MSL tried to put too much in the bag from the beginning,” Stern said, recalling to the audience that it began as a $750 million mission. “We were kidding ourselves as a community and as an agency that you could do that.”

“We need to do this” mission, Stern said, “so we need to come up with the money.”

Stern said no single aspect of the MSL undertaking is to blame for the overrun. “It’s rife through the whole project,” he said, adding that NASA and its contractors underestimated the scope of the task.

“This is a $2 billion mission. It needs to work,” Stern said. If the MSL were to result in “a $2 billion hole in the ground at Mars,” the damage to NASA’s wider Mars Exploration Program would be significant, he said.

Stern said he was unsure what the ultimate bill for MSL would be, noting that the cost-to complete figure was going up monthly.

“I’m not signing the paperwork if I don’t think it’s going to work. I don’t care who else signs the paperwork … I won’t,” Stern told the audience.

He raised the possibility of passing up on the 2009 launch opportunity for MSL if he is not confident the mission will succeed. Launch dates of 2010 and 2011 are possible, he said.

Meanwhile, not everyone thinks that Mars is getting a raw deal.

“There have been multiple missions over the past years, Phoenix on its way, MSL to launch next year, and yet the only message getting out is a whine about ‘cuts’ to what seems to the rest of the solar system community as an entitlement program for Mars,” said Fran Bagenal, a planetary scientist at the University of Colorado in Boulder. “We will not get to Europa or Titan in the next couple decades if Mars continues to take up over 40 percent of the solar system exploration budget.”

Brian Berger contributed to this story from Washingon.