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Landing is key puzzle in Mars trip

Artist concept painting shows NASA's Mars Science Laboratory Curiosity rover on the surface of the planet, July 22, 2011. Landing astronauts safely on Mars is one of the biggest technological hurdles for any future manned mission to the Red Planet, even mLanding astronauts safely on Mars is one of the biggest technological hurdles for any future manned mission to the Red Planet, even more complicated than last year's daring rover touchdown.