Less than a week after landing on Mars, the U.S. Spirit spacecraft has found possible evidence that water once flowed on the now-barren planet, the goal of the mission. The scientists are cautious about their interpretation.

Although the Spirit robotic rover has not yet begun its trek over Martian terrain, one of its scientific instruments has remotely detected small amounts of a mineral in nearby soil that hint of ancient water.

The instrument that did this is an infrared camera designed to sense the composition of material from afar by measuring heat emissions.

Mars mission scientist Phil Christensen says the presence of the mineral, called carbonate, might mean its is a remnant of rocks that formed in water from dissolved carbonate particles.

“So it might be that this carbonate actually does indeed have to do with the water that we came to look for,” he said.

But Mr. Christensen warns that the mineral does not necessarily mean the landing site called Gusev Crater was an ancient lake, as is believed. The carbonate could have come from atmospheric dust that interacted with rocks and soil without water present.

The six-wheeled robotic explorer will help them determine the answer by examining rocks and soil closely when it eventually departs the Spirit lander. The nature of the soil in which the carbonate is found will reveal a lot.

Cornell University researcher Steven Squyres says if it is in wind-blown dust, it probably came from elsewhere and says nothing about a watery past for Gusev Crater. But if the soil that contains carbonate is coarse, like water sediments, that is evidence that the crater is an ancient lake bed.

“I think we’re going to be chasing this carbonate story [for] weeks, months maybe,” he said. “What we can do as we start to head out across the countryside is we can look at different patches of soil and we can measure the carbonate abundance is different kinds of soil.”

The rover’s expedition to do this has been delayed because airbags that cushioned the landing cannot be fully retracted and continue to block its path down Spirit’s front ramp. To get around this obstacle, engineers have decided to rotate the lander one-third of a turn to the right and roll it off a secondary ramp on the lander’s side late next week.

Steven Squyres says his team is prepared to command the rover to dig with its mechanical arm in whatever direction it heads.

“We always knew that we could egress in any direction and that the egress direction was going to be picked on the basis of safety,” he said. “That’s part of why we make sure to get a full 360 degree panoramic view. So we’re going to be ready to pick targets, ready to do science no matter which direction the egress turns out to be.”

In preparation for dispatching the rover, engineers have begun to raise it from its compressed travel position, as if it were a newborn stretching and kicking. The process of expanding the vehicle’s legs and wheels to their fully extended position is taking two days.

This graph, consisting of data from the Mars Exploration Rover Spirit’s mini-thermal emission spectrometer, shows the light, or spectral, signatures of carbonates – minerals common to Earth that form only in water. The detection of trace amounts of carbonates on Mars may be due to an interaction between the water vapor in the atmosphere and minerals on the surface.

Image Credit: NASA/JPL/Arizona State University