What awaited the astronauts when they returned to Earth after the Apollo 11 moon landing?

The trio were quarantined to protect Earth from any germs picked up on the moon.

Before the ticker-tape parades and the heroes' welcome home, Neil Armstrong, Buzz Aldrin and Michael Collins, the U.S. astronauts responsible for successfully putting America's first moon landing in the history books, spent nearly a month in quarantine after returning to Earth.

On July 16, 1969, the trio lifted into space aboard the Apollo 11 and then entered a lunar orbit. By the next day, Armstrong and Aldrin, aboard the lunar module Eagle, had separated from Collins who remained in the command module.

And on July 20, 1969, Americans and the staff at Apollo Mission Control in Houston, Texas, watched and listened in amazement as Armstrong and then Aldrin placed their feet on the moon's surface.

Aldrin told ABC News' David Muir in 2014 that the three men had put odds on their trip because they knew they were actually risking their lives. He said Collins was the last to board for the mission.

"What were the chances that you thought you were gonna be able to successfully land on the moon?" Muir asked.

"So we figure there's about 60%, which we did, not bad," he said.

On the moon, Aldrin and Armstrong took photographs, ran a few scientific tests and by 1:11 a.m. July 21, they were back inside the Eagle with the hatch closed. They slept on the surface of the moon and began their journey back to planet Earth 12 hours later.

Watch the full film "Apollo: Mission to the Moon" at NatGeoTV.com

Back on Earth, the astronauts' families were asked so many questions.

"What kind of plans do you have for Neil when he gets back? A quiet outing or what?" one reporter asked Armstrong's wife, Jan.

"We haven't made any plans yet," she said. "They have to get back."

Armstrong, Aldrin and Collins did make it back, making a dramatic splashdown into the Pacific Ocean at 12:50 p.m. on July 24, 1969.

Afterward, they were quarantined to protect the planet from any germs that they might have picked up from the moon.

They were seen wearing biological isolation garments as they entered a mobile quarantine facility.

Video captured them with their faces pressed against the glass of the facility, greeting President Richard Nixon on the other side.

The men were, in fact, in isolation for three weeks. First, they stayed in a converted Airstream trailer aboard the USS Hornet Aircraft carrier. Then they were transported to Pearl Harbor before finally returning to Houston.

It was there that the men were finally reunited with their wives, who like so many Americans, had been waiting anxiously for them to return safely back to Earth.

In an interview, Collins said that the quarantine effort might have been for nothing. The moment the three men landed in the ocean, they opened the hatch.

"The command module lands in the Pacific Ocean and what do they do? They open the hatch. You gotta open the hatch. All the d--- germs come out!" Collins said in a recent interview for PBS.