The Mars Spirit rover stopped beaming scientific data to flight controllers Wednesday following thunderstorms at an Australian ground station that may have interfered with the daily uplink of critical computer commands.

The rover acknowledged receiving its daily instructions, but during a subsequent overflight of the Mars Odyssey orbiter, Spirit did not transmit science data as expected. Another relay opportunity, this one with the Mars Global Surveyor, began around 11:30 p.m. EST but as of 12:30 a.m., a spokesman for the Jet Propulsion Laboratory said he had been unable to reach flight controllers to confirm whether any data were received.

"Ground controllers were able to send commands to the Mars Exploration Rover Spirit early Wednesday and received a simple signal acknowledging that the rover heard them, but they did not receive expected scientific and engineering data during scheduled communication passes during the rest of that martian day," said a status report from the Jet Propulsion Laboratory in Pasadena, Calif.

"Project managers have not yet determined the cause, but similar events occurred several times during the Mars Pathfinder mission. The team is examining a number of different scenarios, some of which would be resolved when the rover wakes up after powering down at the end of the martian day (around midday Pacific time Wednesday)."

It is possible the glitch has, in fact, been resolved. But JPL's public affairs office is not set up to provide overnight updates from mission control.

During a news briefing Wednesday afternoon, mission manager Jennifer Trosper said the daily transmission of commands to Spirit was affected by thunderstorms at the Deep Space Network's ground station in Canberra, Australia. Whether that had anything to do with subsequent events was not addressed in the JPL status report.

"You've heard about the rain in Spain and how that can cause problems? Well, today it was the rain in Canberra," Trosper said. "When the rover woke up this morning, we were actually over the Deep Space Network station in Canberra, Australia, because that was the part of the Earth that was pointed toward Mars at the time. There was lightning and there was rain and there was a thunderstorm in Canberra.

"The morning timeframe, local solar time at the Gusev [Crater landing] site, between about 9 a.m. and 9:45 a.m., is an important time for us to take all of the work we did overnight, all of the sequences we built, the commands to the rover, we transmit them to the rover and then it will start to act on those about 9:45 local solar time.

"As a result of the rain in Canberra today, the signal strength was not able to be received by the rover and so we weren't able to transmit those commands to the rover. It received a weak signal from Earth because of the rain and so, it actually didn't get all the data we wanted it to get. As a result, the rover did exactly what it was supposed to do, it continued to run yesterday's master sequence, which takes care of the rover in terms of keeping it awake during the day and continues to do communications."

Trosper said she expected to hear from Spirit during an afternoon overflight of the Mars Odyssey spacecraft. But no data were received then, or presumably later, during an evening pass by the Mars Global Surveyor. Another opportunity was available around 1:30 a.m. EST Thursday.

"If necessary, the flight team will take additional recovery steps early Thursday morning (the morning of sol 19 on Mars) when the rover wakes up and can communicate directly with Earth," the status report said.

The next Spirit news conference is planned for noon EST Thursday.