"We have revealed this canyon like no one before us." So proclaims Olivier de Goursac, a French spatial imaging specialist who, along with colleague Adrian Lark, produced the spectacular image (left) of Mars' Valles Marineris, or Mariner Valley. Named for the Mariner 9 satellite that first revealed it some three decades ago, the chasm is often called the Martian Grand Canyon, though at 2,500 miles long, it is actually five times longer (about the span of the continental United States) and as much as four times deeper than Earth's. The image is based largely on satellite data produced by the Mars Orbiter Laser Altimeter (MOLA), an instrument that was launched aboard the Mars Global Surveyor spacecraft in 1996. MOLA measures Martian topography by transmitting a laser beam and tracking the time the beam takes to reach the planet's surface, bounce off, and return (the longer it takes, the lower the altitude of the surface measured). De Goursac and Lark combined that data with evidence about the Martian surface and then used imaging software to generate the landscape. The final result, says de Goursac, astonished even its creators.