The biggest moon rock was only a quarter-inch in diameter and too important to touch.

It was one of the many tiny specimens the astronauts of Apollo 11 collected.

Randy Korotev was an undergraduate chemistry major at the University of Wisconsin at the time. The university was one of the institutions selected to study the chemical composition of the moon pebbles.

So Korotev, then 20, was one of the first privileged few to examine them.

Forty years after that historic lunar walk on July 20, 1969, Korotev, now a lunar geochemist at Washington University, is still studying the rocks Neil Armstrong, Buzz Aldrin and Michael Collins brought back to Earth.

The lunar material sits in a sealed tube at Washington U., locked away for safekeeping.

"It just turned my career in this direction," he said of the historic moon landing. "I've been studying lunar samples ever since."

The moments the astronauts spent on the moon 40 years ago captured the imagination of millions, inspired many to go into science careers and touched off lifelong obsessions for some.

Korotev's study of moon material eventually took him to the deserts of Antarctica. For another St. Louisan, Henry Brownlee, the fascination with space took a different track.

He would become a quality assurance inspector for McDonnell Douglas and work on space shuttle propulsion systems. He now works for Boeing, the company that acquired McDonnell Douglas, as an archivist.

Dr. Bill Hartel, a dentist in Rock Hill, didn't see the lunar landing on television because he was away at summer camp. He was so upset that he made it his mission to meet every astronaut who walked on the moon.

"I'm a space nut," Hartel said.

But the effects of the Apollo mission, and subsequent space missions, go far beyond the fascination of space nuts and scientists. Chances are, they influence your life in some way.

NASA has brought more than 3,500 products to the marketplace as a result of its space program, said David Ritchey, an associate director at the St. Louis Science Center.

Many of those products are now common in everyday life, from freeze-dried food to the materials that keep your home warm.

"A lot of the insulation you have in your house right now is the result of the Apollo program," Ritchey said.

Hartel begged his parents not to send him to summer camp in Wisconsin in 1969. Even at 10, he knew that seeing the stroll on the moon was a once-in-a-lifetime event.

"But we had five kids," he said. "My parents sent me away so I wouldn't be in their hair."

One night, while using newspapers to start a fire, he spotted the headline.

"It said on the paper, 'Men land on Moon,'" he recalled. "I saved it out of the fire."

And so began a quest to meet, in person, every astronaut who ever walked on the moon.

The first he met was David Scott, the commander of Apollo 15. Hartel tracked Scott down at a planetarium in Chicago when Scott was presenting a moon rock to the organization.

Hartel, 20 at the time, furtively searched the museum until he spotted the astronaut. He found him walking out of a restroom, a big cigar hanging out of his mouth.

"I shook his hand," Hartel said. "I got him to sign a picture."

More meetings followed, across the country and even overseas, until Hartel had shaken hands with all 12 men who walked the moon.

Hartel has photographs in his dental office of himself and his children with the lunar astronauts. As patients sit back in the dental chair, they gaze at pictures signed by astronauts, the famous photo of Earth hovering behind the moon's surface, and a picture of Hartel, at 10, standing next to a model rocket.

He's shared meals with some of the astronauts who walked the moon and keeps letters he penned to them over the years.

He can tell you which ones battled alcohol and drug problems, who has since died, who became religious as a result of the experience, and who abandoned religion.

There's one question everyone wants to know but the men hate to answer, Hartel said.

What did walking on the moon's surface feel like?

The best answer he heard came when he traveled to Scotland to meet John Young, who walked on the moon during the Apollo 16 mission and was giving a lecture.

"The kids asked him, 'What was it like?'" Hartel said. -"'Great. You should do it. It was fun.' Those were the words he said."

SILENT SUPPORTERS

Brownlee was just 3 years old when Apollo 11 landed on the moon, but he remembers lying on his parents' couch with a toothache, watching Armstrong walk across the lunar surface.

When Brownlee thinks about the Apollo missions, what strikes him is the thousands of people who toiled on the projects in relative anonymity - the behind-the-scenes engineers, scientists and workers who made it possible to explore space.

Nearly everyone remembers the names of Armstrong and Aldrin, but how many can recall the third man, Collins?

It was Collins who piloted the command module while Aldrin and Armstrong took their historic steps. "He is like the silent man who made it happen," Brownlee said.

Today, Brownlee is preserving history and educating future generations about his company's history.

And he still recalls watching NASA shuttle launchings on television over the years, knowing that he had played a role.

"It creates a real level of pride," he said.

ROCKS ON ANTARCTICA

Lunar rocks haven't come just from NASA missions. Small moon chunks have fallen to Earth for billions of years, blasted off during asteroid collisions. They are preserved in arid climates, where water can't erode them.

Korotev's career of studying moon rocks took him to the deserts of Antarctica, where scientists have discovered most lunar meteorites.

The study of meteorites and lunar samples has helped provide a clearer picture of events on Earth billions of years ago.

"If big things were hitting the moon, you can bet big things were hitting the Earth," Korotev said. "We think of the moon as a recorder of early solar system history."

For decades, geologists have been trying to figure out what killed off so many species on Earth 65 million years ago. In 1969, few would have considered that it was a meteor impact, Korotev said.

"Now pretty much everybody accepts it," he said.

A few years ago, Korotev set up a website about lunar meteorites. He gets four to five e-mails a day from people all over the world who think they've found a lunar rock.

"In 2008, I was contacted 978 times," he wrote on the site. "These totals do not include the gentleman from Sweden who sent me 2,077 e-mails."

So far, none of the e-mails or phone calls has led to an actual lunar meteorite.

But Korotev keeps hoping.