Sixty years after its birth, NASA remains a rare unifying force.

The space agency opened for business on Oct. 1, 1958, two months after its creation by the passage of the National Aeronautics and Space Act of 1958.

During the ensuing six decades, NASA has managed to inspire people throughout the country and around the world without getting too bogged down by partisan politics or the conflicts and controversies that have affected other branches of the U.S. government. [NASA's 10 Greatest Science Missions]

"NASA is one of the best — I hate to use the word, but I'll say it — brands that this country has," said John Logsdon, a professor emeritus of political science and international affairs at George Washington University's Elliott School of International Affairs in Washington, D.C. "It's projected an image of the United States that's really positive, and that reflects how we want to see ourselves — as a country of people who accomplish difficult things."

In terms of U.S. government activities, "there's been much less controversy about NASA than almost anything else," Logsdon told Space.com. "There never has been, and is not now, an anti-NASA lobby or interest group or public group. At a minimum, people say about NASA, 'Yeah, that's a good thing.' And a fair number of people say, 'That's great — that's what we should be doing.'"

Exploring the heavens

NASA's continued occupation of this rarefied air traces back to its founding document. The newly created agency's first objective, as laid out in the National Aeronautics and Space Act of 1958, involves "the expansion of human knowledge of phenomena in the atmosphere and space."

Though the Act does direct NASA to preserve the United States' leadership role in space science and technology, it also instructs the agency to facilitate "cooperation with other nations and groups of nations in work done pursuant to this Act and in the peaceful application of the results thereof." [Celebrate NASA's 60th Birthday with These Space Videos!]

And, in contrast to most previous space-related research in the United States and abroad, the military would not be leading the way.

"The United States wanted to make it clear that our space program was a civil effort and scientific effort," NASA Chief Historian Bill Barry said in a 60th-anniversary video posted by the space agency on July 29.

That effort has been famously fruitful. Just 11 years after its founding, NASA put boots on the moon. A total of 12 astronauts walked on the lunar surface during the Apollo era, and the agency brought all of them safely back to Earth.

NASA astronauts flew 135 space shuttle missions from 1981 through 2011. Many of these flights helped build or service the International Space Station (ISS), the orbital outpost that has hosted rotating astronaut crews on a continuous basis since November 2000. NASA has been a driving force behind the ISS, a multinational effort involving more than a dozen partners, from the very beginning.

Pluto, as seen by NASA's New Horizons spacecraft during its epic flyby of the dwarf planet in July 2015. (Image credit: NASA/JHUAPL/SwRI)

And then there are the robotic exploration missions — far too many to rattle off here, even as a bare-bones list. NASA spacecraft have studied the sun up close and visited every currently or originally recognized planet, from Mercury all the way out to Pluto, as well as some asteroids, comets and dwarf planets. (Many NASA spacecraft have also studied their home planet from Earth orbit over the years, of course.) The agency has put a host of landers and rovers on the moon and Mars as well. [Destination Pluto: NASA's New Horizons Mission in Pictures]

NASA in situ exploration now extends into interstellar space: The far-flung Voyager 1 probe popped free of the sun's sphere of influence in August 2012, and its twin, Voyager 2, is poised to do the same soon.

And we can't forget the many astrophysics missions — such as the Wilkinson Microwave Anisotropy Probe and the Hubble, Chandra and Spitzer space telescopes — that have brought distant, mysterious objects into clear view and reshaped astronomers' understanding of the universe's structure and evolution.

Also on the astrophysics side: The Kepler space telescope has found about 70 percent of the 3,800 known exoplanets, and its recently launched successor, the Transiting Exoplanet Survey Satellite, may be even more prolific.

The discoveries made by all of these missions have opened eyes around the world — and so have the gorgeous photos delivered by Hubble, the Saturn-orbiting Cassini spacecraft and many other NASA probes.

The next 60 years

NASA will continue to do groundbreaking robotic exploration for decades to come. But the agency's cultural and societal influence may wane in the future as private spaceflight matures and starts doing big things in the flashy realm of crewed exploration, Logsdon said. [NASA's 60th Anniversarsy Puts Its History Office in the Spotlight]

Those big things may include helping to establish human settlements on Mars and other deep-space destinations, as both SpaceX and Blue Origin — which are led by the billionaire entrepreneurs Elon Musk and Jeff Bezos, respectively — aim to do.

But NASA is working to send humans out into deep space as well, something the agency hasn't done since the Apollo 17 astronauts returned from their moon mission in December 1972. This push really began in 2004 with President George W. Bush's Vision for Space Exploration, which called for NASA to retire the space shuttle program by 2010 and put boots on the moon again by 2020.

"We have not argued since then that going beyond Earth orbit is the right thing to do," Logsdon said. "We've been slow about doing it, but there hasn't been a counter-argument."

NASA's current plan involves the construction of a small space station in lunar orbit by the mid-2020s. The outpost, known as the Lunar Orbital Platform-Gateway, will serve as a jumping-off point for missions to the moon's surface, both robotic and crewed. And, NASA officials say, the skills learned during the construction and operation of the Gateway will help humanity get to Mars, which the agency aims to do in the 2030s, in cooperation with international and commercial partners.

This journey to Mars could end up being the grandest adventure of the 21st century, one that future generations recall more clearly, and with even greater reverence, than the gray-haired among us regard the Apollo missions.

Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.