The famed Mars rovers, Spirit and Opportunity, are still going, four years after they landed on the rusty Martian surface. But the scientists and engineers who run them from Earth say they’ve had a few heart-stopping moments in the last several days. Yesterday I got a message from one of the mission managers, preferring not to be identified, saying a letter had come from NASA headquarters in Washington: "Headquarters has just directed the Mars Exploration Rover project to take a budget cut of $4 million in this fiscal year, as a cost-saving measure for the Agency. This cut, if implemented, would force us to halt science operations, probably within the next few weeks, for one of the two healthy rovers now on Mars." I reached Steve Squyres, the Cornell astronomer who is the Principal Investigator for the rovers. He said they had gotten together a meeting of the rover team, and a lot of people were badly shaken. There might be hundreds of job cuts, he said. And they would send one of the rovers — probably Spirit, which is struggling through a cold Martian winter — into hibernation, and hope that funding is restored for the next fiscal year beginning in July. By the time I reached NASA management, they were ready to tell a completely different story. "I was just in a meeting with Mike Griffin [the NASA Administrator]," said Dwayne Brown of the public affairs office, "and you can quote him: ‘We are not shutting down a rover.’" That said, NASA does confirm its Mars program is in financial trouble, and there will be cutbacks. The next planned lander, an ambitious mission in 2009 called Mars Science Laboratory, is badly over budget, and other projects will suffer to make up for it. But the two rovers, which have survived for so long, caught people’s imagination, and even if they are gradually breaking down (one of Spirit’s wheels no longer turns), people want to see them keep going.