No planet has teased the imagination as much as Mars.

In ancient Greece and Rome, the planet's fiery red hue made skywatchers think of their god of war. That fascination continues today .

Was there ever any life on Mars? What was it like? Is there any possibility that there is life there now?

Early this afternoon, NASA's Mars Polar Lander touches down on the surface of the red planet. Scientists will get a chance to get the answers to many questions.

The Polar Lander has been hurtling through hundreds of millions of kilometres of space for the past 11 months.

It's hoped that the $200 million Polar Lander will help solve an old mystery -- whether there's ever been life-sustaining water on Earth's nearest planetary neighbour.

The American space ship is being navigated by radio signals from the Jet Propulsion Laboratory.

"It's a very complex process," says Sam Thurman, flight operations manager.

"There are literally years of effort by hundreds of different people behind making those five minutes of events happen."

Once on the surface, the craft's instruments will be deployed - some to test the atmosphere, others to claw out samples of dust and, possibly, ice.

For the first time ever, NASA has included a microphone on a spacecraft sent to Mars, an idea originally proposed by astronomer Carl Sagan.

There are fears that the costly mission could hit a rock or lose contact with NASA scientists back home.

"The biggest risk ... is Mars itself," says Sarah Gavit, NASA project manager.

"We have never been to the south pole of Mars before and we're not exactly sure what we are going into."

Frozen water exists on Mars in its northern ice cap. But scientists believe there may be more underground.

The Polar Lander will try to find evidence that the atmosphere was once warmer and thicker. Its landing site is believed to be an area where climate changes caused layering of dust and ice that can be read like the rings of a tree trunk.

Any answers from the probe would help focus future missions searching for past or present life, which is dependent on water, though the Lander's instruments cannot detect fossils or living organisms.

1. Who has teased the imagination as much as Mars?