Prof. Peter Schultz, a planetary scientist at Brown University, wears 3-D glasses used to view the image of the lunar landscape behind him.

The Providence Journal / Connie Grosch

The spacesuit-clad body clung tantalizingly to a ladder in a blurry, grainy black-and-white television picture until its wearer finally plopped himself onto the surface of the moon. Entranced watchers on Earth inhaled collectively at what the future may regard as the most momentous step taken by a human being. The 40th anniversary of Neil Armstrong’s pioneering encounter with another heavenly body is fast approaching.

An exhibit to commemorate the events of July 20, 1969 opens Saturday at the John F. Kennedy Presidential Library in Boston. It contains models of the Gemini and other early spacecraft, and videos of JFK, including the speech in which he called for the country to put a man on the moon within a decade.

After the lunar landing, NBC estimated that 123 million Americans were cemented to their television screens when Armstrong’s voice knifed through a quarter-million miles of cosmic static to declare: “One small step for [a] man, one giant leap for mankind.”

The moment has taken on the gravitas of such thunderclap episodes as the attack on Pearl Harbor, the assassination of John F. Kennedy, or the terrorist attacks of 9/11, which became engraved on the mind.

The Evening Bulletin, former sister paper of The Providence Journal, commemorated the occasion with the memorable headlines MAN ON MOON, and, in later editions, MAN OFF MOON.

Carle Pieters remembers it, but not from watching it.

Pieters, now a professor of geological sciences at Brown University, was in the Peace Corps. She listened to the goings-on via radio with students on the island of Borneo.

“We didn’t have TV,” she said. “I was thrilled and the students with me were thrilled. They particularly noticed that the literal translation of Armstrong is ‘strong arm,’ and that impressed them.” In the United States it was nighttime when Armstrong descended, but on the other side of the planet it was day.

“It was an amazing thing to participate in history,” Pieters said. “It wasn’t until I got back, of course, that I saw the video clips of him stepping out. That was before I became an astronomer.”

Did the experience influence her career choice?

“I think it influenced everybody at the time. For me it just solidified my deep interest to be actively involved in science.”

These days Pieters is the lead scientist for one of the two NASA instruments aboard Chandrayaan-1, the first Indian satellite to orbit the moon and one of NASA’s first steps toward returning humans to the moon after a decades-long pause.

“A lot has happened since then,” she said. “I’m pretty much doing the same thing now except we have instruments that have grown in their capabilities. We have an instrument orbiting the moon — the moon mineralogy mapper. We measure reflected solar light and analyze it in 240 colors. Our eyes can only detect red, green and blue and combinations. With this instrument we take a spectrum that includes both visible lightwaves and longer wavelengths where the eye can’t see. From a scientist’s point of view, it’s a lot of fun.”

PETER SCHULTZ remembers that first lunar step well.

Now a planetary scientist at Brown, Schultz was in Austin, Texas, where his professor-adviser was part of the Apollo Program.

“When I was a kid, they used to call me Satellite Sam because I was pretty much obsessed with the space program,” he said.

“When Armstrong stepped out it was just disbelief. By that time the Apollo 10 had gone around the moon, and the Christmas Apollo — Apollo 8 — that one really got me. It was the first time we really had a good idea of what the far side looked like. I actually sat down and had dinner with the Apollo 13 astronauts a month after they returned. I was much more interested in what they saw on the far side than that they nearly got killed. That’s where my head was.

“But with that Apollo 11 landing, all of us had tears in our eyes. I was with my wife, my professor who eventually went to NASA headquarters in charge of the Hubble, and his wife. It was a very nice evening. We just simply watched the whole process from start to finish.”

Nowadays Schultz is involved with the next moon mission — LCROSS, a lunar crater observation remote sensing satellite.

“The launch is in early June, probably colliding with the moon in October.”

The idea is to smash an impactor into the shadowed floor of a crater. “We want to dig below the surface to see if we’ve got ice,” he said. If so, it makes a difference in terms of bringing your own water with you or process what’s already there. Forty years later, and I’m still kicking.”

SHERWOOD C. “Woody” Spring has some memories of that day, too. Rhode Island’s own astronaut, Spring, a native of Glocester, had just returned from his first tour of duty in Vietnam as an Army helicopter pilot.

“I had lost touch with the news — you’re in a whole different world when you were in Nam,” he said. “I was a space cadet at West Point. In Nam I just forgot about it. You were still in a different world for the first three or four months after you got back. I was visiting my cousin in Miami and it was on the news. I said, ‘Oh my God — they’re on the moon!’ ”

Spring, now retired from the Army and the astronaut corps and living in Lorton, Va., is a professor of systems engineering at the Defense Acquisition University.

He’s not sure that the sight of Armstrong stepping onto the moon was what prompted him to become an astronaut because, as he put it, he was kind of in the same field anyway.

Does the event have cosmic significance?

“Those were the good old days,” he said. “Now Atlantis, my shuttle, is on its last flight. I had the second flight.

“You know you’re getting old when your spacecraft retires.”

tmorgan@projo.com