President Barack Obama delivers a speech at the Operations and Checkout Building at NASA Kennedy Space Center in Cape Canaveral, Florida on Thursday, April 15, 2010.

Given how far NASA lies down the food chain of White House priorities, it's always welcome when a president engages in a discussion of space policy.

And that's what President Obama did on Tuesday when he authored an op-ed that appeared on CNN.com and called for America to take a "giant leap" by sending humans to Mars in the 2030s.

And a landing on Mars will follow."

The similarity of his words, spoken six years apart, gives us a chance to judge his administration's space policy, and the verdict is pretty straightforward: Obama has set NASA and the United States on a course to Mars.

It is an easy thing to say "We are going to Mars," however, and a far more difficult thing to do it.

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