WASHINGTON (AP) â€” A revamped Mars exploration program that includes a search for water and for evidence of life will include six robot missions to the red planet and the return of rock samples possibly by 2011.
As part of an effort to recover from two failed missions in 1999, the National Aeronautics and Space Administration announced plans Thursday for Mars expeditions that include robotic orbiters, landers and wheeled vehicles that may explore many miles of the planet.
Scott Hubbard, the Mars program director, said the reorganized efforts were directed toward a fundamental question: ``Did life arise there, and is life there now?''
NASA science director Ed Weiler said the robot missions to Mars would be pathfinders for sending people there.
We are preparing the way for humans, eventually, to go to Mars,'' Weiler said. There are no current plans, however, for a manned mission.
Three robot missions â€” an orbiter next year and two robotic surface rovers in 2003 â€” already were planned. Thursday's announcement added another orbiter in 2005, an elaborate mobile science lab in 2007 and a ``Scout'' mission in 2007.
Hubbard said the new Mars exploration plan phases in increasingly complex scientific and engineering efforts, building toward the ability to land a robot on Mars, scoop up rock samples and return them to Earth. Plans now specify sample-return missions in 2014 and 2016, but early mission successes could advance a sample return to 2011, officials said.
``We have to seek before we sample,'' Hubbard said.
He said missions in this decade will concentrate on finding the best spot on Mars to pick up rock samples.
The new sample return mission is years later than originally expected. Prior to the two 1999 failures, the space agency had proposed to launch a sample return mission by 2005.
The design of the Scout mission is still undecided, but it will be based on proposals being collected from scientists. Current proposals include such exotic plans as instrument-laden balloons that drift around Mars for months or an airplane that explores the planet's valleys and canyons.
NASA had to reorganize its Mars exploration plans after the failure last year of two robot craft, the $125 million Mars Climate Orbiter and the $165 million Polar Lander. An independent analysis concluded that the agency attempted to do too much with too little, and flawed engineering resulted. It recommended the program's complete reorganization.
Weiler said the agency closely followed recommendations of the independent analysts in a seven-month study and redesign of the Mars program.
``We've checked off every box'' in the report, Weiler said.
New discoveries also helped shape the plans. A spacecraft now in orbit of Mars took photos this year that suggested a relatively recent flow of water. Earlier photos had shown clear evidence that water existed on Mars in the ancient past, but the new photos showing eroded gullies suggested that there might still be underground reservoirs.
Louis Friedman, executive director of the private Planetary Society, said NASA ``has done a good, but limited, job with their new plan.''
Friedman said he was disappointed the agency failed to plan for a ``permanent robotic presence on Mars'' or for a manned mission.
``Until they do,'' Friedman said in a statement, ``the program will continue to be underfunded and less purposeful than it should be.''
Weiler said details for missions beyond those set for 2001 and 2003 were not firm so that NASA could respond quickly to new discoveries on Mars.
``Mars had a tendency to surprise us,'' he said, and the agency wants to be able to adjust mission plans so that new findings can be exploited.
Weiler said the current plans would spend about $450 million a year, but the sample return mission may cost as much as $1 billion.
On the Net: Mars exploration: http://mpfwww.jpl.nasa.gov/
The Planetary Society: http://www.planetary.org/
American Association for the Advancement of Science: http://www.aaas.org/