For thousands or even millions of years, rivers, lakes and deltas coursed across the surface of Mars, according to data sent from the planet over the past few weeks.

The Jet Propulsion Laboratory reported Wednesday that its scientists have concluded that the Red Planet was once awash in -- well, water. NASA said the findings are further spurring interest in searching not only for elements that could support life but also for evidence of past life.

"The minerals present in Mars' ancient crust show a variety of wet environments," Brown University professor John Mustard, a member of the investigative team, said in a statement. "In most locations, the rocks are lightly altered by liquid water, but in a few locations they have been so altered that a great deal of water must have flushed though the rocks and soil. We're finding dozens of sites where future missions can land to understand if Mars was ever habitable and if so, to look for signs of past life."

Close-up photos of the planet and the results of Mars experiments were sent down to the NASA scientists from the Mars Reconnaissance Orbiter. While the spacecraft has been orbiting the planet, NASA's Mars Lander has been on the surface of its northern pole for the past month and a half, running its own experiments. This week, the Lander's robotic arm is scraping up shavings from ice found in a trench that the arm's scoop dug in the soil. Scientists have put the robotic arm through several test runs to make sure it can scrape up the ice shavings and move them into an onboard analysis oven before the ice can evaporate into the Martian atmosphere.

The Mars Lander is expected to gather and analyze soil and ice samples from the northern pole of the planet for a total of three months. Late in June, NASA scientists found what they'd been hoping for - ice, a key element in supporting life.

Then six days later, the scientists announced that they'd found that the Martian soil contained minerals that are essential to supporting life. The dirt was found to be very alkaline, with a pH level of between eight and nine. It also contained magnesium, sodium, potassium and chloride. NASA reported that the minerals in Martian soil are typical of soils here on Earth.

Now the orbiter is sending back information showing that water was on Mars as far back as 4.6 billion to 3.8 billion years ago, according to NASA's announcement on Wednesday. The Jet Propulsion Laboratory noted that the period corresponds to the earliest years of the solar system. And the wet conditions were evident for thousands to millions of years after the waters formed clay, which later was buried by volcanic lavas.

NASA said the scientists also found evidence of a system of river channels that flowed into a crater lake slightly larger than Lake Tahoe in California.

"The distribution of clays inside the ancient lakebed shows that standing water must have persisted for thousands of years," says Bethany Ehlmann, a Brown graduate student who is also a member of the investigative. "Clays are wonderful at trapping and preserving organic matter, so if life ever existed in this region, there's a chance of its chemistry being preserved in the delta."