Mark Edward Kelly is a retired American astronaut, engineer, and retired U.S. Navy Captain. He is the husband of former Congresswoman Gabrielle Giffords, and is an author, political activist, and aerospace executive and consultant. A naval aviator, Kelly flew combat missions during the Gulf War. He was selected to become a NASA Space Shuttle pilot in 1996 and flew his first mission in 2001 as pilot of STS-108. He piloted STS-121 in 2006 and commanded STS-124 in 2008 and STS-134 in 2011. STS-134 was his final mission and the final mission of Space Shuttle Endeavour. His wife was the target of an attempted assassination in Tucson, Arizona, on January 8, 2011. After the shooting, in which six people were killed, both Kelly and Giffords were thrust into the media spotlight. His wife's shooting led to a broad national conversation ranging from the duties of a husband to what is acceptable civil discourse. Kelly's identical twin brother, Scott Kelly, is also an astronaut. The Kelly brothers are the only known siblings to have both traveled in space. In 2015, Scott Kelly began a mission spending a year in space on the International Space Station. He returned to Earth on March 1, 2016, after 340 days in space. During and after Scott's year-long mission, the brothers were studied to find physical differences caused by living in space versus a baseline on Earth.