A glitch with a Mars orbiter relaying commands from Earth delayed plans for the Phoenix Mars Lander's second day of activities on Tuesday, NASA officials said.

The Mars Reconnaissance Orbiter turned its UHF radio off, possibly because of a cosmic ray, cutting off communications with the lander, said Fuk Li, manager of the Mars exploration program for NASA's Jet Propulsion Laboratory in Pasadena, Calif.

But Li and others said it is not a significant problem.

"All this is is a one-day hiccup in being able to move the arm around, so it's no big deal," said Ed Sedivy, space program for Lockheed-Martin Corp. in Denver.

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Li said the orbiter was programmed to respond as it did, but that orbiter team members were trying to get the radio back on. It has a second radio aboard that might be used instead, though reprogramming would be needed.

A second orbiter, the Mars Odyssey, is to be the primary relay for returning data to Earth from the lander, which is parked in a valley in Mars' northern arctic region.

If necessary, the Odyssey will do double duty, relaying commands to the lander as well as taking up the earthbound information.

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Since landing on Mars on Sunday, Phoenix has delighted scientists with the first-ever peek of the planet's unexplored northern latitudes. The terrain where Phoenix settled is relatively flat with polygon-shaped patterns in the ground likely caused by the expansion and contraction of underground ice.

Peter Smith of the University of Arizona, the mission's principal researcher, and his colleague Alfred McEwen, who operates the camera aboard the Mars Reconnaissance Orbiter, said photos taken since the landing show that Phoenix is at the edge of a trough that will make an ideal place for digging.

Smith said plans had called for maneuvers Tuesday to unhook the lander's 8-foot robotic arm from a protective sleeve that held it in place.

That movement will be delayed by a day because of the radio outage, but Smith also said a spring in a latch holding the arm in place had activated and opened wider, "so I think we don't have a problem."

The arm is at the heart of the lander's scientific functions during its three-month experiment.

Phoenix will dig into the soil with the arm to reach ice believed to be buried inches to a foot deep, as part of the effort to study whether the site could have supported primitive life.

Among the things it will look for is whether the ice melted in Mars' history and whether the soil samples contain traces of organic compounds, one of the building blocks of life.

Smith said it would be "hard to conceive" that there isn't ice beneath the lander, given that the landscape is 80 percent ice for the first meter of ground.