Hello Mars? Can You Hear Us Now?

NASA engineers got a half-hour of transmissions Friday morning from the Spirit rover and planned further communications to try to diagnose and possibly patch up their ailing robotic patient on Mars.

NASA heard from the six-wheeled rover for 10 minutes at about 4:30 a.m. PST and received data for 20 minutes about an hour later.

"The spacecraft sent limited data in a proper response to a ground command, and we're planning for commanding further communication sessions later today," Pete Theisinger, rover project manager at NASA's Jet Propulsion Laboratory, said in a statement early Friday.

Officials did not immediately elaborate on the signals. If they contain significant data, the transmissions would mark the first such signals in two days — a period of anxious waiting for scientists after normal communications halted Wednesday.

Engineers hope Spirit will manage to send some engineering data, which can be used to assess the health of the spacecraft, pinpoint any problems and allow NASA to begin working on a potential fix or fixes.

Scientists and spokesmen at the Jet Propulsion Laboratory did not immediately return calls seeking comment on Friday. The statement said Friday's signal was received by NASA's Deep Space Network antenna complex near Madrid, Spain.

Since Wednesday, its 19th day on Mars, the Spirit has sent back to Earth only meaningless radio noise or simple beeps acknowledging receipt of commands.

Among the possible causes: "It could be a command problem, it could be something to do with the flight software on board the vehicle, or it could be a hardware problem, and we need to be able to track down which one of those it is," said Dr. Randy Wesson, a project engineer.

If the problem lies with the rover's hardware, the situation could be beyond repair.

Baffled scientists struggled to pinpoint the trouble.

"It is precisely like trying to diagnose a patient with different symptoms that don't corroborate," said Firouz Naderi, manager of NASA's Jet Propulsion Laboratory Mars exploration program.

Wesson said there's a duplicate of the Rover at JPL, and it's being used to diagnose the problem.

"We will put in the program that it was running and feed it the same set of commands, and see if we can get it to "safe" — to shut down — and once we can duplicate the failure mechanism, then we can figure out what set of commands we need to do to wake it back up," he said.

Spirit is one-half of an $820 million mission. Its twin probe, Opportunity, is expected to land on Mars late Saturday at a site halfway around Mars from Spirit, in a region called Meridiani Planum," Theisinger's statement Friday morning.

The twin rovers are supposed to examine the Red Planet's dry rocks and soil for evidence that it was once wetter and more hospitable to life.

Meanwhile, Europe's Mars lander has been missing since its deployment last month, but its orbiter Friday sent confirmation of water ice at the south pole.

Until Wednesday, Spirit had functioned almost flawlessly and NASA scientists and engineers had been jubilant.

Cushioned by its air bags, the rover made a bull's-eye landing, surviving what was by far the most dangerous part of the mission — the descent through the atmosphere at 12,000 mph. Then on Jan. 15, in another nail-biting moment for NASA, the rover safely rolled down a ramp onto Mars' ruddy soil without becoming snagged.

It has snapped thousands of pictures, including breathtaking panoramic views and microscopic images of the martian soil. It also carried out preliminary work analyzing the minerals and elements that make up its surroundings.

The mission's main scientist, Steven Squyres of Cornell University, cautioned that communications problems are common on spacecraft.

The problem surfaced while Spirit was preparing to resume analysis of its first rock, just a few yards from where it landed.