The twin Mars rovers have survived everything the Red Planet could throw at them for four years: massive sandstorms, blistering-hot days and freezing nights.

But perhaps their greatest feat has been accomplished millions of miles away on Earth: surviving NASA budget cuts.

On Monday, news got out that the space agency would cut $4 million from the rovers' annual budget of $20 million, prompting officials to plan putting Spirit into hibernation and limiting Opportunity's travel.

Then, shortly after noon yesterday, NASA reversed course and pledged to keep them going.

The past two days have been a roller coaster for mission scientists nationwide, including Rongxing Li and his team of Ohio State University mapping specialists, who have helped guide Spirit and Opportunity across Mars' rocky landscape.

"The mission has been so successful," Li said. "You don't want to let it just hibernate."

Successful is an understatement. The rovers, which landed in 2004, were supposed to last about three months. NASA engineers thought Martian dust would build up on their solar panels, killing power. Now, they believe strong winds blow off the dust.

Money, however, has proved a bigger challenge.

But NASA spokesman Dwayne Brown said yesterday that a letter proposing the cuts, which was sent to the agency's Jet Propulsion Lab, was not an order, just an idea.

Steve Squyres, a Cornell University planetary scientist and the mission's science director, called the issue "a little hiccup."

"The budget in the Mars program is tight. Each day is a gift," Squyres said. "What I'm doing right now is trying to keep the team focused on getting the most out of the rovers we can get today."

Right now, plans include a risky mission for Opportunity to study rock layers at the base of a 30-foot cliff, where some areas are blocked from sunlight.

"If you are a solar-powered rover, shadows are going to be a scary place to be," Squyres said.

shunt@dispatch.com