This week, retired astronaut Mark Kelly announced he is running for the Arizona Senate seat once held by John McCain. If he's successful, he'll join a small club of congressmen who have traveled in space:

John Glenn

John Glenn blazed the trail both in space and on Capitol Hill. He was the first American to orbit Earth back in 1962 and became the first astronaut elected to Congress in 1974. Glenn spent 25 years as a senator from Ohio, and in his last term he returned to space in 1998 at the age of 77.

Jack Schmitt

Before he was elected to represent New Mexico in the Senate, Jack Schmitt was the last human to walk on the moon. While on the Apollo 17 mission, Schmitt snapped a picture of Earth known as the Blue Marble – perhaps the most famous photo of our planet.

Jack Swigert

Jack Swigert is responsible for one of the most famous lines in NASA's history. Twelve years after he and the crew of the Apollo 13 safely returned to Earth after their ill-fated lunar mission, Swigert was elected represent Colorado's sixth House district. He died before he was sworn in.

Jake Garn

Jake Garn became the first sitting member of Congress to visit space. The Utah senator was head of the subcommittee overseeing NASA when he flew aboard space shuttle Discovery in 1985.

Bill Nelson

Former Florida Sen. Bill Nelson traveled to space in 1986 while he was a member of the House of Representatives. Nelson said the experience of space flight and looking back at our planet, changed his perspective.

If Mark Kelly wins the Democratic nomination for Arizona's Senate seat, he will likely face another high-flyer in the general election: Sen. Martha McSally, who currently holds the seat, is the first female fighter pilot to fly a combat mission in Air Force history.