The story behind the 'fireflies' that astronaut John Glenn saw in space

PHOTOS: The life and career of John Glenn Astronaut John Glenn, Jr. is loaded into the Friendship 7 capsule in preparation for flight on the Mercury Titan rocket February 20, 1962. Click through to see more events from the life of one of the last surviving astronauts from the golden age of manned spaceflight... less PHOTOS: The life and career of John Glenn Astronaut John Glenn, Jr. is loaded into the Friendship 7 capsule in preparation for flight on the Mercury Titan rocket February 20, 1962. Click through to see more ... more Photo: NASA/Getty Images Photo: NASA/Getty Images Image 1 of / 95 Caption Close The story behind the 'fireflies' that astronaut John Glenn saw in space 1 / 95 Back to Gallery

News of the death of famed American astronaut John Glenn has brought back a flood of nostalgia for the early days of NASA manned spaceflight.

The 95-year-old ex-astronaut and U.S. senator was the last living member of the original Mercury Seven crew of test pilots turned astronauts.

On Feb. 20, 1962, Glenn became the third American in space, following colleagues Alan Shepard and Gus Grissom who went to space on separate but brief missions in 1961.

Glenn’s trip into low-earth orbit inside the Friendship 7 space capsule, though, would make him the first American to actually orbit our planet for an extended period of time.

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If you have seen the 1983 space race epic “The Right Stuff” you might remember the scene with Mercury Seven astronaut John Glenn (played by Ed Harris) seeing “fireflies” outside of the Friendship 7 as he made three passes around the big blue marble.

That film, directed by Phillip Kaufman, depicted the fireflies as a mystical almost alien presence surrounding Glenn's tiny tin can.

In real life as Glenn stared in awe at the glowing bits, mission control was worried that it was pieces of the capsule’s heat shield disintegrating, possibly dooming the Marine to be the first man to die in space. After all he was reaching speeds of nearly 17,000 miles per hour.

From the radio transcript of Glenn’s Friendship 7 mission:

John Glenn: "This is Friendship Seven. I’ll try to describe what I’m in here. I am in a big mass of some very small particles that are brilliantly lit up like they’re luminescent. I never saw anything like it. They round a little; they’re coming by the capsule, and they look like little stars. A whole shower of them coming by.

They swirl around the capsule and go in front of the window and they’re all brilliantly lighted. They probably average maybe 7 or 8 feet apart, but I can see them all down below me, also."

CAPCOM: "Roger, Friendship Seven. Can you hear any impact with the capsule? Over."

John Glenn: "Negative, negative. They’re very slow; they’re not going away from me more than maybe 3 or 4 miles per hour. They’re going at the same speed I am approximately. They’re only very slightly under my speed. Over. They do, they do have a different motion, though, from me because they swirl around the capsule and then depart back the way I am looking."

It took Glenn nearly five hours to circle the globe three times, splashing down safely into the Atlantic Ocean near Bermuda.

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Later that year when Glenn’s colleague Scott Carpenter made the same trip on the Aurora 7 capsule he also saw the fireflies.

NASA scientists deduced they were really just illuminated frost flakes that had accumulated on the outside of the capsule as it burst out of the earth’s grasp and began to fall away, looking like what could be fireflies to the untrained human eye. Carpenter was able to tap the walls of the capsule and make the flakes float off.

The Friendship 7 capsule is currently on display at the National Air and Space Museum in Washington, D.C. It’s incredibly small, showing just how cramped Glenn was during his ride around the Earth.

Glenn holds the distinct honor of being the first Marine in space.

Later in Oct. 1998 at the age of 77 he became the oldest man to fly in space when he served as a payload specialist aboard the Space Shuttle Discovery. He was also the first man to drink Tang in space during the 1962 mission, setting sales off of the powdered drink for years to come.

When Carpenter died in 2013 Glenn became the last surviving member of the original Mercury Seven crew.