NASA's engineers have shown the world yet again their capacity to be great.

Their plan to deliver the 1-ton rover Curiosity to the surface of Mars was bold, audacious, unprecedented - and, early on Monday, successful.

It garnered well-deserved kudos from all around, including the top: "It proves that even the longest of odds are no match for our unique blend of ingenuity and determination," President Barack Obama said.

While it's clear NASA can still do great things, what's less clear is how much greatness the agency has left.

On Friday the space agency took a big step toward ceding low-Earth orbit to commercial spaceflight companies, providing $1.1 billion to SpaceX, Boeing and Sierra Nevada to develop spacecraft to fly humans into space. This was widely viewed as an important step in bringing NASA out of its post-shuttle hangover, during which it has had to rely on Russian transport to and from its International Space Station.

What's next?

Yet after Curiosity's success, NASA itself has few major events planned - its new Orion spacecraft could launch an unmanned test flight in 2014, but it will fly on a commercial rocket. And even if NASA's own larger rocket, now on the drawing board, survives a decade of political change, it won't fly until at least 2021.

"It's always a good thing when NASA pulls off an incredibly complex and difficult challenge," said Jim Muncy, a space consultant who runs PoliSpace. But, he noted, there's not many major, attention-grabbing missions coming for awhile, during which time it may be difficult to maintain broad political support for the agency.

The need to find funding in NASA's budget for the James Webb Space Telescope, the cost of which has risen from $1.6 billion a decade ago to $8.7 billion, has caused NASA to delay or cancel other interesting projects.

"The problem is that the James Webb Space Telescope costs so much that we're not going back to Mars anytime soon," he said. "NASA's big programs tend to eat their young."

Few dispute that NASA can do great things. The issue, for many, is that they're not sure what NASA is going to do - it has yet to articulate a destination for humans beyond low-Earth-orbit or say when it will get there.

Just last week, very senior Apollo program leaders were passing around a Yogi Berra quote, by email, that expressed their frustration with the space agency: "If you don't know where you are going, you might not get there."

In the meantime there's a belief that commercial companies might pass NASA by. Elon Musk, chief executive of SpaceX, says he'd like to land humans on Mars in 12 to 15 years.

Experts to weigh in

With some of these concerns about NASA's future in mind, the prestigious National Research Council has appointed a blue-ribbon committee to assess whether the strategic direction of NASA remains viable.

The group's charge is simple: "Do the agency's activities and organization efficiently and effectively support that direction in light of the potential for constrained budgets for the foreseeable future?"

Paul Spudis, a senior scientist at the Lunar and Planetary Institute in Houston, said Curiosity's success doesn't change the fact that the agency is still looking for a vision.

"It's tangential to the agency's fundamental problem - where is it going and why?" Spudis asked. "Since (2010) NASA has been floundering in strategic aimlessness and national irrelevance. Only the momentum of existing programs started long ago, like the International Space Station and Mars Science Laboratory, are keeping it alive at all."

True believers

That view wasn't universally held, however, as some NASA supporters dispute the idea that Curiosity represents a peak for the space agency.

They say the agency is in the midst of a difficult transition from the long space shuttle era to a time when NASA will be partners with commercial providers. And they believe this partnership will allow America to go further than ever before.

"The spectacular success of the Curiosity landing reinforces the reality that NASA remains a truly excellent organization," said space historian John Logsdon, former director of the Space Policy Institute at George Washington University.

"Coupled with the recent SpaceX/NASA Dragon mission to the International Space Station, NASA is demonstrating its status as the global leader in space."

Many inside the space agency also viewed Monday's feathery landing of Curiosity on Mars as an indication that spaceflight can still be bold.

Stan Love, an astronaut and planetary scientist, said NASA gets a bad rap for being too conservative, for not daring as much as it did in the Apollo era. Of the high-risk Curiosity landing, Love said, "NASA takes a lot of criticism for being timid and unwilling to undergo risks."

"Well, this puts that criticism to bed."