Nearly two decades after its automated Viking spacecraft made the first dramatic landings on the surface of Mars, the United States is preparing to renew its exploration of the Red Planet.
With an eye toward manned landings on Mars in the 21st century, the National Aeronautics and Space Administration is about to launch a sophisticated orbiter -- called Mars Observer -- that may yield much more about the planet's weather, terrain and geology.
Unlike the Viking landers -- which scooped up and analyzed Martian soil in a fruitless search for signs of life -- the Mars Observer will not carry out any biological investigations.