Traces of carbonate minerals showed up in the rover's first survey of the site with its infrared sensing instrument, called the miniature thermal emission spectrometer or Mini-TES. Carbonates form in the presence of water, but it's too early to tell whether the amounts detected come from interaction with water vapor in Mars' atmosphere or are evidence of a watery local environment in the past, scientists emphasized.

"We came looking for carbonates. We have them. We're going to chase them," said Dr. Phil Christensen of Arizona State University, Tempe, leader of the Mini-TES team. Previous infrared readings from Mars orbit have revealed a low concentration of carbonates distributed globally. Christensen has interpreted that as the result of dust interaction with atmospheric water. First indications are that the carbonate concentration near Spirit may be higher than the Mars global average.

After the rover drives off its lander platform, infrared measurements it takes as it explores the area may allow scientists to judge whether the water indicated by the nearby carbonates was in the air or in a suspected ancient lake.

"The beauty is we know how to find out," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the mission. "Is the carbonate concentrated in fluffy dust? That might favor the atmospheric hypothesis. Is it concentrated in coarser material? That might favor the water hypothesis."

Spirit accomplished a key step late Thursday in preparing for rolling off the lander. In anticipation, the flight team at NASA Jet Propulsion Laboratory in Pasadena, Calif., played Bob Marley's "Get Up, Stand Up" as wake-up music for the sixth morning on Mars, said JPL's Matt Wallace, mission manager. In the following hours, the rover was raised by a lift mechanism under its belly, and its front wheels were fully extended. Then the rover was set back down, raised again and set down again to check whether suspension mechanisms had latched properly.

Pictures returned from the rover's navigation camera and front hazard-identification camera, plus other data, confirmed success.

"We are very, very, very pleased to see the rover complete the most critical part of the stand-up process," Wallace said. Next steps include retracting the lift mechanism and extending the rear wheels.

A tug on airbag tendons by the airbag retraction motor Thursday evening did not lower puffed up portions of airbag material that are a potential obstacle to driving the rover straight forward to exit the lander. The most likely path for driving off will be to turn 120 degrees to the right before rolling off. "This is something we have practiced many times. We are very comfortable doing it," Wallace said.

The earliest scenario for getting the rover off the lander, if all goes smoothly, is Spirit's 13th or 14th day on Mars, Jan. 16 or 17.

"We're proceeding in a measured, temperate way," said JPL's Peter Theisinger, project manager for the Mars Exploration Rover project. "This is a priceless asset. It is fully functioning. It is sitting in a beautiful scientific target. We're not going to take any inappropriate risks."

While preparing to learn more about what Mars rocks are made of, Christensen announced an educational project to involve school children and other people in getting rocks from all over Earth for comparison. "Send me your rocks and we'll see if there are rocks in your back yard that are similar to what we're seeing on Mars," he said. Information about how to send rocks to Arizona State University is on the rovers' Web site at

http://marsrovers.jpl.nasa.gov/home/index.html

Spirit's twin Mars Exploration Rover, Opportunity, will reach Mars on Jan. 25 (Universal Time and EST; Jan. 24 PST). The rovers' main task is to spend three months exploring for clues in rocks and soil about whether past environments near the landing sites were ever watery and possibly suitable to sustain life.

JPL, a division of the California Institute of Technology, manages the Mars Exploration Rover project for NASA's Office of Space Science, Washington.