The probe, designed to search for water in the form of ice or vapour on the Martian surface, will touchdown softly on the fine dust of "gentle, rolling plains" in a target area 198km (124 miles) long by 19km (12.4 miles) wide near the planet's south pole.

The Lander carries equipment to test soil samples for traces of water

Scientists know water once flowed freely on Mars - this mission's objective is to find out what happened to it.

The probe also carries a microphone, which for the first time will allow scientists to hear sounds from the surface of another planet.

The Lander is due to touch down on 3 December at the site 76 degrees latitude south and 195 degrees longitude west. A backup site is located nearby.

(Click here to see a Nasa photograph of the landing site)

As the probe arrives, the planet's southern hemisphere will be approaching the beginning of its summer allowing the spacecraft's solar panels to function throughout the day.

The landing site is expected to be different from the rocky surface encountered by Pathfinder

"We chose a location with some surface features, but no cliffs or jagged peaks, because the spacecraft will be able to land safely, yet we'll still accomplish our science goals," said Project Scientist Dr Richard Zurek, of Nasa's Jet Propulsion Laboratory in Pasadena, California.

He said the site, about 800km (400 miles) from the pole itself, appears to have layers of dust and ice that will provide a record of the Martian climate much like reading tree rings.

"In addition, we may find evidence of soil particles that formed in ancient seas on Mars and were later blown into the polar regions."

Mars surveyor

From the archive: Jean Bennett-Powell reports on Nasa's most ambitious mission yet to the Red Planet

The site is expected to be very different from the rocky surface pictured by the earlier Pathfinder and Viking landers.

The site was chosen by scientists examining data sent back by the Mars Global Surveyor which is currently orbiting the planet.

That probe has already revealed some astonishing features of the planet, including a crater so deep it could swallow Mount Everest, and another that has been nicknamed the Happy Face Crater because of markings similar in appearance to a simple, smiling human face.

Mars' "Happy Face Crater" pictured from the Mars Global Surveyor

Launched on 3 January this year, the Polar Lander also carries with it two "microprobes" known as Deep Space 2.

They will launch from the main craft about five minutes before it enters the planet's atmosphere, then smash into the planet surface to study the Martian soil from beneath the surface.

The Mars Polar Lander forms the third phase of Nasa's long-term programme for the robotic exploration of Mars.

Groundbreaking mission

The programme began with the groundbreaking Pathfinder mission in 1996 which sent back vivid pictures of the planet's barren surface.

Three months later, Mars Global Surveyor began to map the planet from orbit.

Scientists hope that additional missions planned every two years will lead to a manned voyage to Mars as early as 2015.

The purple elipse shows the primary landing site, the backup is shown in white. Photo: NASA/JPL/Caltech ex mission website