On Oct. 4, 1957, the Soviet Union pulled off one of the greatest propaganda triumphs in history. For the first time ever, it put a satellite into earth orbit, catching the United States by surprise and kicking off the space age.

Sputnik’s steady radio beep-beep-beep relayed no scientific information, but it clearly told the world that the United States was behind in the race to space. And it stayed behind for some time. It was the Soviet Union that launched the first human into orbit in April 1961.

The United States needed a goal, a big one. So on May 25, 1961, President John F. Kennedy told a joint session of Congress: “Now it is time to take longer strides — time for a great new American enterprise — time for this nation to take a clearly leading role in space achievement . . . I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the Earth.”

It would prove hugely expensive (about $25 billion, $200 billion in today’s money). Previously unthought-of equipment had to be designed and tested. The Saturn V rocket developed for the Apollo program remains to this day the tallest, heaviest and most powerful rocket ever to fly. It cost $185 million (over a billion in today’s dollars) just to launch each one.

There were other great, non-monetary costs. On Jan. 27, 1967, during testing of the command module of Apollo 1, fire broke out and astronauts Gus Grissom, Roger Chaffee and Ed White were asphyxiated.

Finally, on July 16, 1969, a Saturn V soared up from the Kennedy Space Center, carrying Apollo 11 into space. A million people watched. Three days later, the lunar module passed behind the moon, fired a rocket and entered into lunar orbit.

The next day, as the eyes of the world remained glued, the lunar lander, “Eagle,” touched down in the Sea of Tranquility. “Houston,” Neil Armstrong reported, “Tranquility base here. The Eagle has landed.”

At 2:56:15 UTC, 10:56 EDT, Armstrong set foot on the moon, soon joined by Buzz Aldrin. The two astronauts planted an American flag, deployed a seismometer to measure moonquakes, placed a mirror so that a laser could measure the exact distance to the moon, and gathered samples of rocks and regolith (the powdery lunar soil).

After just a couple of hours, the two were back in the lunar lander, preparing for sleep. Then, 21 hours after landing, the craft began its ascent to the command module in orbit.

Apollo 11’s three astronauts splashed down in the Pacific on July 24. To guard against the very remote chance they’d brought lunar pathogens back with them, they were held in isolation for three weeks.

The scientific accomplishments of the Apollo program were relatively modest, especially considering the huge cost. But then, that had not been the real object of the program. Rather it had been to supercharge the American space effort and bring it victory in the space race. It had done that.

The essentially propagandistic nature of the Apollo program can be seen by the fact that no man has walked on the moon since 1972. Unmanned space probes, which cost a tiny fraction of manned ones, have, since Apollo, increased our knowledge of the solar system by several orders of magnitude.

Will humans return to the moon some day? Surely the answer is yes. The technology of space travel has greatly increased since 1972 and costs have been much lowered by such aborning technologies as reusable rockets. Your cellphone has far more computing power than Apollo 11 had.

A manned expedition to Mars would be a vast — and vastly expensive — undertaking. Mars never comes closer to earth than 100 times the distance to the moon (and the physics of space travel would require a far longer trajectory to the Red Planet and back).

But humans for a million years and more have wondered what was in the next valley and gone to find out. We will, one day, go to Mars and beyond. It is part of our very deepest human nature to explore, and the final — and greatest — frontier beckons.

John Steele Gordon writes for Commentary.