A、2001 B、2007 C、2011 D、2017 C

Washington (dpa)-After the failures of their past two Mars missions, U. S. space officials announced a departure Thursday from their "cheaper, faster, better" strategy, saying they would send six robots to explore the Red Planet over the next 15 years.
   However, they don’t envision obtaining soil samples from Mars until 2011 to try to ascertain whether there is water on the most Earth-like planet in our solar system and, possibly, life.
   The top scientists of the National Aeronautics and Space Administration (NASA) said in Washington that they envision two-year rotations of robotic surface missions and orbiting satellites.
   The Mars schedule laid out Thursday indicated a more tentative approach to Mars exploration after the embarrassing failures at the end of last year of the Mars Polar Lander and the Mars Climate Orbiter within three months of one another.
   Ed Weiler, head of NASA’s office of space science, said the first leg of the new programme is to come next year with the launch of the satellite 2001 Mars Odyssey.
   Two years later, two robots will be sent to explore the surface of Earth’s neighbour, then, in 2005, the Satellite Mars Reconnaissance Orbiter will circle the Red Planet while outfitted with a supercamera, capable of photographing objects the size of a football, Weiler said.
   In 2007, NASA plans to deploy a "Smart Lander", which could carry 270 kilograms of equipment and be able to avoid obstacles, like rocks, at landing using jet engines and sensors.
   Weiler said that in the decade thereafter, small aircraft and even balloons could be sent close to Mars’ surface and long- range rovers and robots would be deployed to collect soil and return it to Earth with a rocket.
   For these later robot missions, NASA would cooperate with European space officials, especially in Italy and France. However, France’s science minister, Roger-Gerard Schwartzenberg said Thursday in Paris that he would like to bring soil samples back to Earth by the end of this decade.
   The interest in soil samples has intensified since the Mars Global Surveyor, which is now orbiting Mars, sent back pictures in June that showed signs of water on the Red Planet.