The longest serving astronaut in history, who flew twice to the moon and commanded the first space shuttle mission, has announced his retirement after 42 years at NASA.
John W. Young, 74, announced Tuesday his plans to leave the space agency on Dec. 31.
Young was the first human to fly in space six times and the only astronaut to pilot four different spacecraft. He flew in the Gemini, Apollo and space shuttle programs. More info at ABC News