Few features on any planet loom as large -- in telescopes or in the minds of scientists -- as the huge scar on Mars known as Valles Marineris. To call the apparent drainage system a series of valleys is like calling the Grand Canyon a gully. And to claim you know just how it came to exist is a recipe for much scientific wrangling.

We simply don't know a lot about Mars' past.

Nor its present. Even after many spacecraft landings on Mars and hundreds of thousands of satellite pictures, there is no good ground-level snapshot showing what Valles Marineris looks like today.

Now an artist has offered several views of the region, its deep canyons and towering cliffs, all based on topographical data obtained by the Mars Orbiter Laser Altimeter (MOLA) instrument on NASA's Mars Global Surveyor spacecraft.

Scientists caution that the renderings should not be used to make scientific interpretations about Valles Marineris. But NASA has released the images to the public because they are rendered from solid scientific data.

The artist's impressions are the work of Olivier de Goursac of the French Mars Society and Adrian Lark, who used computer software to interpret the topographical information.

The renderings provide several views of how things might look in various parts of a sprawling complex of valleys, which on Earth would stretch from Los Angeles to New York.

"My goal was to obtain the most natural-looking views, as if an astronaut was standing on the surface of Mars, or as if we were flying above Valles Marineris," de Goursac told SPACE.com. "Also, the dust opacity of the Martian atmosphere is accurately rendered and all colors and luminosity were very carefully balanced to be as close as possible to reality."

David E. Smith, the principal investigator for MOLA at NASA's Goddard Space Flight Center, stressed that the images were not produced by NASA. The raw MOLA data are measurements of elevation, resolving features down to about 600 meters in size. The data do not reveal individual rocks, nor do they show the position of the Sun.

"The texture, color and lighting effects have been added to make these very attractive images of Mars," Smith said. "This additional information was not provided by us or by any other instrument on the spacecraft."

Smith said there is probably some vertical exaggeration in the images as a result of the rendering process.

"I suppose it's rather like looking at a surface a long way away through a telescope or telephoto lens of a camera, so some distortion occurs," he said.

Leading scientists believe massive ancient floods carved Valles Marineris, named after the Mariner spacecraft. But there is no consensus on when or exactly how the features formed. Was it water? Ice? Mud? Huge periodic lava flows may also have contributed to the look of the region.

Also controversial and intriguing is whether water is still sculpting gouges into the valley system today. Evidence collected over the past few years increasingly hints that water may sometimes burst to the surface from liquid or frozen underground deposits.

One of the new renderings is done from the bottom of the Melas Chasma, looking at canyon walls that soar nearly 6 miles (9,500 meters) high. The Melas Chasma floor is being considered as a possible landing site for one of two NASA rovers scheduled to reach Mars in 2004.

Click to see all the new renderings

Next Page: Details about how the renderings were created