As NASA's space shuttle program winds down, President Obama is urging the agency to change its tired, old ways and reach for something bigger...like Mars, or perhaps an asteroid.

The three-decades old program is set for completion after the shuttle Atlantis takes off on its final mission Friday; dependent, as always, on the weather. With the program's departure, so goes some 7,000 Kennedy Space Center jobs.

Mr. Obama told participants in a Twitter town hall at the White House Thursday that he's got much more in mind for the space agency.

"[W]e've set a goal to-- let's ultimately get to Mars," the president said. "A good pit stop is an asteroid. I haven't actually -- we haven't identified the actual asteroid yet, in case people are wondering," he added to laughter.

The president's mission to Mars idea isn't new-- he unveiled it last year-- but the timing of the Twitter question couldn't be more relevant.

"Now that the space shuttle is gone, where does America stand in space exploration?" the president was asked.

The president said he's been urging NASA to re-think its way of doing things.

"We're still using the same models for space travel that we used with the Apollo program 30, 40 years ago. And so what we've said is, rather than keep on doing the same thing, let's invest in basic research around new technologies that can get us places faster, allow human space flight to last longer," he said.

The future of low-orbit space travel is expected to fall to private companies and U.S. astronauts may have to hitch a ride on Russian capsules, but those ventures have become routine, Mr. Obama said, and he urged NASA to broaden its horizons.

Still, the president indicated it's important not to underestimate America's stature in the final frontier, telling the town hall, "We are still a leader in space exploration."