Controllers were supposed to beam commands to the rover through a Deep Space Network antenna in Canberra, but rain and lightning made for a weak signal, and "it actually didn't get all the data," said mission manager Jennifer Trosper at NASA's Jet Propulsion Laboratory in Pasadena.
Instead, Spirit continued to use a day-old sequence of commands that kept it awake and communicating but not moving or using its instrument-tipped robotic arm.
"Not a lot of science was done today, but the rover is in a very safe state. It's healthy," she said.
Rain was expected to continue in Canberra for a day or two. Whether that would delay attempts to have Spirit use its arm to drill into a rock was unclear.
NASA wants the six-wheeled vehicle to grind away a tiny area of the weathered face of a rock dubbed Adirondack (search). The rock beneath could offer clues to Mars' geologic past.
Spirit landed on Mars Jan. 3 on a two-pronged mission to find out whether the now-dry planet was wetter and hospitable to life long ago. Spirit's twin, Opportunity, is scheduled to land on Mars on Saturday.
On another issue, mission members said the Red Planet, as seen in gorgeous panoramic shots from the rover, may not be really red.
The photos of bright red dust, rusty rocks and salmon sky were color-balanced to approximate what a person might see standing on the martian surface, but it may be weeks before scientists perform the calculations to show true color, said Ray Arvidson of Washington University, a scientist on the project.
Mars was sort of a medium chocolate brown in photos taken by the Viking landers in 1976, he said.