For some UC Berkeley scientists, looking at soil from Mars is like looking at a key to the planet's climate history.

By analyzing soil samples from Mars, scientists have determined that water on the planet came from the its atmosphere, rather than from deep within the ground, as was previously believed.

The discovery, led by Ronald Amundson, a UC Berkeley professor of soil science in the department of environmental science and policy management, gives new insight into the planet's climate that may reveal more about whether life ever existed on Mars.

"The soil acts as a museum, a long-term record of climate information that the climate has experienced," Amundson said.

The team of scientists from UC Berkeley, NASA and other science institutions analyzed the salt distribution of soil collected from five Mars missions.

Amundson said analysis of the salt distribution in the soil suggests water on the planet came from the atmosphere by rain or dew. Scientists who previously interpreted the soil content believed the water moved up from sources deep in the ground.

The salt distribution of the planet's soil shows that the water on Mars came from the atmosphere first and traveled down through the soil, Amundson said. Since chloride salt, which is more soluble, is found in larger concentrations beneath sulfate, the less soluble salt, Amundson said scientists could tell water reached the surface of the planet first, dissolving most of the chloride while leaving behind most of the sulfate as the water moved into the ground.

In other research, NASA sent a spacecraft to the planet in May that uncovered icy soil last week, stirring excitement in the science community.

Data released from NASA showed that the planet could support life, as evidenced by soil analyses.

"The ongoing Phoenix mission illustrates how the (spacecraft) has landed on a fantastic, very cold landscape that has a lot of frozen water below the surface," Amundson said.

In the UC Berkeley study, Amundson used soil samples collected in Chile's Atacama Desert to interpret the salt distribution on Mars's soil. Since the two locations have similar extreme climate conditions, scientists could draw the analogy between the salt distribution in the desert soil to that of the planet.

Amundson said scientists can learn through soil comparisons between the two locations, and that he plans to go back to the Atacama Desert to collect more data samples.

"Earth has very close similarities to what we're learning on Mars," Amundson said. "We can take a look at the Mars information to see if we can offer expanded interpretations about ... the Martian path (of salt deposits)."

Tags: MARS, RONALD AMUNDSON, NASA