Who was the only person to fly in both the Mercury and the Space Shuttle programs?

John Herschel Glenn Jr. (July 18, 1921 – December 8, 2016) was a United States Marine Corps aviator, engineer, astronaut, businessman, and politician. He was the third American in space, and the first American to orbit the Earth, circling it three times in 1962. Following his retirement from National Aeronautics and Space Administration (NASA), he served from 1974 to 1999 as a Democratic United States Senator from Ohio.

He was one of the Mercury Seven, military test pilots selected in 1959 by NASA as the nation's first astronauts. On February 20, 1962, Glenn flew the 'Friendship 7' mission, becoming the first American to orbit the Earth, the third American and fifth person in history to be in space.

Glenn resigned from NASA in January 1964. A member of the Democratic Party, Glenn was first elected to the Senate in 1974 and served for 24 years, until January 1999. Aged 77, Glenn flew on Space Shuttle 'Discovery' STS-95 mission, making him the oldest person to enter Earth orbit, and the only person to fly in both the Mercury and the Space Shuttle programs. Glenn, both the oldest and the last surviving member of the Mercury Seven, died at the age of 95 on December 8, 2016.