NASA

Before Mark Kelly was a Democratic-party US Senate candidate for Arizona, he was a high-flying NASA astronaut with some literally out-of-this-world space credentials.

Kelly announced his campaign for Congress on Tuesday with a video that references his spaceflight experience.

"Seeing that sunrise from space for the very first time, it is incredible," Kelly said. "You know, it's pretty obvious pretty early when you get into space that we're all kind of in this together."

Kelly, 54, is running for the seat formerly occupied by Sen. John McCain. Martha McSally, a Republican former Arizona representative, is currently filling the Senate seat by appointment following McCain's death in 2018. The seat will be up for a special election in 2020.

Kelly, who was originally a Navy pilot, spent 54 days in space serving on four NASA space shuttle missions to the International Space Station. As pilot and later commander, Kelly helped deliver equipment, supplies and crew members to the ISS.

Those shuttle flights were notable for carrying the pressurized module for the Japanese Kibo laboratory to the station in 2008 and the Alpha Magnetic Spectrometer particle physics detector up in 2011.

Enlarge Image NASA

Kelly is the husband of former Congresswoman Gabby Giffords, who survived a shooting in Arizona in 2011 that left six others dead. Both Giffords and Kelly have advocated for stricter gun control in the US. Kelly retired from NASA later that year to focus on his wife's recovery.

Kelly and his twin brother Scott are both retired NASA astronauts. They participated in a NASA twins study involving comparing Scott during a year in space on the ISS with Mark, who stayed down on Earth.

Mark Kelly can look to a notable precedent in astronaut-politicians: John Glenn. Glenn became the first American to orbit the Earth in 1962. He won an Ohio Senate seat in 1974 and served until 1999.