Eight weeks ago, Spirit had yet roll off the lander onto the surface of Mars but the view was grand. Today, March 4, 61 Sols after landingMartian Sols are 24 hours plus 39.5 minutes longSpirit is rolling across Mars, a surrogate geologist. For Dr. Nathalie Cabrol, planetary geologist with the SETI Institute and NASA Ames Research Center, this is a dream ongoing, a dream come true. Recently, I had an opportunity to again interview Nathalie, and learn more about her personal experience exploring Mars. She looked both jubilant and tired.

The engineers and scientists operating this grand machine are living and working on Mars time. Their day starts and ends with dawn and dusk on Mars, almost 40 minutes later each day. On occasion, most of us enjoy sleeping in, but consider moving your schedule 40 minutes later each day. After 18 days, breakfast is at dinner time, and after 36 days, youve cycled around the clock. The plan was for the scientists and engineers at JPL to work 4 days on, 1 day off. For Nathalie Cabrol, exploring Gusev Crater has been her lifes work. Shes been on Mars time since the beginning of January, and working with the team daily. Nathalie likes to arrive 3-4 hours early to analyze the data, and then join the team as the Sun rises on Gusev Crater and Spirit wakes up. So, shes been "on Mars" 16-18 hours each day. Its her lifes work, her passion, and she would not have it another way.

The scientists and engineers are working as one great team, according to Nathalie, and Spirit is like a child with an especially large, extended family. People all over planet Earth are watching her progress, and the nearest relatives are all working together at JPL making sure that Spirit proceeds carefully. Smiling, Nathalie described a bumper sticker on an engineer-friends car. It says, "My other car is on Mars." She has high praise for the engineers driving, planning and maintenance skills. "They love their baby, and refer to the rover as she."

She surveys the terrain from eye-level cameras sending home human-scale images. So far, thousands are collected in the Spirit archives. She collects photons from the distant Sun, converting them to battery power to drive her wheels, operate her tools, and send home messages to us. Recently, she paused to spin her wheel and excavate a shallow trench, discovering more of the interesting rounded granules embedded in the subsurface soil. These little round sand grains appear in the surface soils as well. They may be smoothed by wind or water, or result from volcanic eruption. There are lots of questions about these little Martian marbles, but definitive answers await more data and exploration.

The next major target for Spirit is the Bonneville crater, a meteor-impact crater about 200 meters in diameter and 15 to 20 meters deep. Spirit does not carry a drill to core down below the surface to seek the strata that might reveal the presence of water now or in the past. Spirit and her sister, Opportunity, are seeking evidence of water in the rocks and minerals they assess. But, nature has already excavated the surface with a meteor strike, and Spirit simply needs to get over to the crater and climb down the side to see whats below the surface. Amongst many tasks, Nathalie hopes that Spirit can look for more of the rounded grainssee if they are embedded in a particular layer of the strata, or if they are more common throughout the material revealed in the crater wall. Will the rover be able to descend into the crater? The team will know when Spirit arrives at the rim and sends home images of the crater wall and floor.

Spirit can traverse about 30 meters per day, and the scientists want to stop off at all the interesting places along the way to sample the rocks, dig little trenches, RAT the rocks to look at them up close. They want to "sniff the roses." The engineers could be tempted to let the rover rolljust how far can she go in a day? They want to see what their baby can do. Its a compromise of desire. The whole team works plans together to make tracks across Gusev. When there is a pause in the engineering work, scientists organize presentations for the team to explain the questions they are asking, and the data they are gathering. The engineers take great care to explain how the rover works, and how each piece functions for the scientists. With sincerity, Nathalie describes the scientist-engineer partnership as based on great mutual respect that results in terrific synergy.

Spirit is driving across basalt now, and sampling the ejecta from the Bonneville impact on the traverse. Where did the basalt originate? Did it arise from fissures in the floor of Gusev Crater, or was it eroded from the highlands and carried into the crater by water? In the distance, Spirit can see a mesa that is actually the delta coming from Maadim Vallis about 26 km away. Was the basalt carried into Gusev by water flooding out of Maadim Vallis? Its to far away for Spirit, and so the mesa remains on the horizon reminding the team that this mission is about water. The questions and discussions continue unabated, and the excitement of daily discoveries keeps Nathalie and her colleagues energized. Exploring Mars up close through the eyes of Spirit is a "once in a lifetime experience" says Nathalie. "Its addicting. I cant stay away and take a day off, not when I can experience something new each morning on Mars."

How long will Spirit continue as the little rover that could? The factory warranty is for 90 Sols, and servicing (anything besides software) on this robot is obviously impossible. So the team works carefully to plan each days progress, each stop, each collection of science data. I asked Nathalie how the solar panels are holding up. Overtime, dust will accumulate on the surface of the panels, and they will be less efficient at converting sunlight into stored power. And, with fall approaching, the Sun is lower in the Martian sky which results less energy hitting the panels. As time goes on, it will take longer to recharge the batteries. All that said, Nathalie is confident that the Rover will just keep going and going.

Whats her ambition for Spirit? About 2 kilometers east of Bonneville, there are hills she wishes to explore. Here, Nathalie, expects to see ancient terrain. Learning more about those hills can tell us about the history of Gusev Crater. Was there ever water here? The evidence may be found inside the Bonneville Crater and at the hills beyond. Theres so much to see and do on this alien world that feels so much like home to Nathalie. "There are moments when its just spectacular. To see the hills and the mesa on the horizon was just wonderful. I explore deserts as often as I can here of this planet, and Gusev feels like deserts I know, except that its so much more than I had hoped for. Its beyond words. Its fantastic."