If NASA ignores Mars for a decade, it runs the risk of a brain drain, said Ed Weiler, who resigned last year as NASA's sciences chief because of budget battles over Mars.
"Landing on Mars is a uniquely American talent and there aren't too many things that are uniquely American," Weiler said.
In 19 tries, Russia has had little to no success when it comes to Mars. The European Space Agency currently has a spacecraft circling the planet but its lander crashed. NASA has had six Martian failures during its 20 tries.
The Europeans are talking to the Russians and Chinese to replace the U.S. in the upcoming missions.
Earthlings have been captivated by Mars since the 1900s when amateur astronomer Percival Lowell saw what looked like canals. The life question was tackled by the twin Viking spacecraft, which landed in 1976. Their rudimentary experiments failed to turn up signs of life and NASA lost interest.
After a 1992 return attempt failed, NASA came up with a blueprint for Mars: Each mission followed up on discoveries found in the previous flight, and all focused on water, a key element for life.
"It's become a more interesting planet every time we go back there," said Wesley Huntress, who spearheaded the new Mars program and went on to run NASA's sciences division.
NASA's Mars program: http://mars.jpl.nasa.gov/
Alicia Chang reported from Pasadena, Calif. Follow her at http://twitter.com/SciWriAlicia .
Follow Seth Borenstein at http://twitter.com/borenbears
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