NASA scientists are sweating over what will be one of the most complicated spacecraft landings ever attempted.

The Curiosity Rover launched late last year, and it's on course to make contact with Mars as scheduled.  But the last few minutes of its flight are the most crucial.

NASA even produced a video to explain the never-before-attempted landing, and the final approach, dubbed, "7 Minutes of Terror."

SOUNDBITE: Tom Revellini, EDL Engineer: "Entry, descent and landing, also known as EDL is known as the 7 minutes of terror.  Because we've got literally 7 minutes to get from the top of the atmosphere to the surface of Mars, going from 13,000 miles an hour to zero in perfect sequence, perfect choreography, perfect timing, and the computer has to do it all by itself, with no help from the ground. If any one thing doesn't work just right: it's game over!"

As Curiosity enters the atmosphere, the spacecraft's computer will guide it like an airplane to land in a very narrow space on Mars.

The spacecraft's heat shield has to be ejected or else its instruments can't guide the craft to the surface.

The largest supersonic parachute ever built by NASA is to soften the descent but it doesn't slow it down enough to land.

So, computers cut off the parachute at a precise moment, and activate rockets.

The rockets have to divert the rover away from the parachute, aiming it toward a crater, next to a nearly 4-mile high mountain.

But the rockets can't be on at landing because the dust they'd create could damage the sensitive equipment on board.

So, NASA has developed a "sky-crane" to lower the rover below the spacecraft with a 21-foot long tether.

Then, the rover is placed gently on the Martian surface, on its wheels.

The spacecraft, with the rockets, must be guided to move away and crash, far enough away, so it doesn't damage the rover.

It's hoped Curiosity will explore the surface of Mars for nearly 2 years.

And the purpose of the mission?

SOUNDBITE: Michael Meyer, Lead Scientist, NASA Mars Exploration Program: "Going to Mars, one of the main reasons for going there is to figure out whether or not life ever started there.  And the one big implication would be: If in the 2nd place in our solar system that we think life has a possibility and actually did start there, my conclusion would be that life is easy. It's a natural process.  And that the universe is just littered with places that have life. And I think that would be a pretty spectacular finding."