John Young, the ninth human to ever walk on the moon, died at the age of 87, NASA confirmed on Saturday. The cause of his death is unknown.

Young was only one of three astronauts to fly to the moon twice, having set foot on the moon during the Apollo 16 mission on April 27, 1972. He also orbited the Moon as part of Apollo 10. 

Young was also noted as the first ever commander of the Space Shuttle program, leading STS-1 on board of Space Shuttle Columbia in 1981. 

According to NASA, Young went to space six times as part of the Gemini, Apollo and Space Shuttle programs.

"John was one of that group of early space pioneers whose bravery and commitment sparked our nation's first great achievements in space." NASA administrator Robert Lightfood said. "But, not content with that, his hands-on contributions continued long after the last of his six spaceflights -- a world record at the time of his retirement from the cockpit."

Young retired from NASA in 2004 after 42 years of being employed by NASA.