NASAs newly announced plan to capture an asteroid and re-position it around the moon for an astronaut visit sounds cool, but its a side-show on the road to Mars, scientists and long-time space mission managers told Congress.

To me, the connection between the asteroid retrieval mission, which involves proximity operations with a rock that would fit comfortably in this hearing room, I see no obvious connection between that and any of the technologies and capabilities required for Martian exploration, Cornell University planetary scientist Steve Squyres told the House Subcommittee on Space on Tuesday.

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A better stepping-stone for human expeditions to Mars is the moon, argued Paul Spudis, senior scientist with the Lunar and Planetary Institute in Houston.

It has partial gravity like Mars. It has a dust environment that you have to learn to deal with. You can learn how to explore and how to get the most out of the missions, Spudis said.

NASA planned to follow the space shuttle and International Space Station programs with a return to the moon, but President Obama canceled the project, known as Constellation, in 2010 due to funding shortfalls.

NASA salvaged Constellations heavy-lift rocket and deep-space Orion capsule and set about crafting a more flexible exploration initiative that would first send astronauts to an asteroid and eventually to Mars.

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President Obamas spending plan for NASA for the fiscal year beginning Oct. 1 requests $105 million to begin work on a revamped asteroid mission which combines a robotic precursor spacecraft to fetch a 23- to 33-foot diameter asteroid with a follow-on expedition by astronauts.

NASA has not yet said how much the asteroid-retrieval mission would cost, but expects it would be less than the $2.65 billion estimate made last year by the California Institute of Technologys Keck Institute for Space Studies.

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NASA's Asteroid Mission a Dead-End to Mars?