Once the Polar Lander reaches Mars it will begin scooping up soil samples
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CNN's John Zarrella reports on the vehicle that will go looking for water on Mars
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CAPE CANAVERAL, Florida (CNN) -- NASA officials were keeping an eye on the weather on Sunday afternoon, hoping conditions would be favorable for the launch of the latest Mars probe.

NASA forecasters said Saturday that bad weather could delay the launch of the Mars Polar Lander until at least Monday. There was a 30 percent chance the probe could be launched Sunday, officials said.

The Mars Polar Lander, which will be sent into space aboard an unmanned Delta rocket, is scheduled to reach the red planet in December, setting down on three legs near Mars' south pole. It is the companion craft to Mars Climate Orbiter, which was launched last month and is already 4 million miles from Earth.

Polar Lander will be the first NASA craft to land on Mars since Pathfinder, which bounced down in an equatorial region of the planet in July 1997, capturing the world's attention and imagination.

The Polar Lander will scoop up and analyze Martian soil to see if any ice is present -- an attempt to prove an hypothesis that water was once abundant on the planet.

"This is really the search for where all the water went that we think once existed and flowed on the surface of Mars," said project manager John McNamee. "It's gone somewhere."

If the water didn't all evaporate, geologists believe the most likely place to find it is at one of the planet's poles. This mission is the first visit ever to a polar region of Mars.

Finding water would be a blockbuster discovery, because water must be present for even primitive forms of life as we know it to evolve. While the Polar Lander can't detect life, its instruments can sniff out ingredients necessary to get life started.

"We'll scoop up some of the soil either on the surface or down a few inches or down a foot or two, and we'll bring it over, and we'll dump it into an instrument," said Peter Smith of NASA's imaging team.

The soil samples will be cooked in NASA's version of an Easy-Bake Oven. If there's ice in the soil, it will melt and turn into water vapor, which can be detected by onboard instruments.

As it makes its way to the Martian surface, a camera on Polar Lander will snap images of its descent through the atmosphere and its landing. Once on the ground, the vehicle will spend 90 days scraping and digging the soil and photographing its surroundings.

Correspondent John Zarrella contributed to this report.