Astronaut James Irwin (1930-1991) gives a salute on the Moon, 1971.Artist: NASA

Astronaut James Irwin (1930-1991) gives a salute on the Moon, 1971. Irwin, pilot of the Lunar Module, gives a military salute while standing beside the deployed U.S. flag during the Apollo 15 lunar surface extravehicular activity at the Hadley-Apennine landing site. The flag was deployed toward the end of EVA-2. The Lunar Module Falcon is partially visible on the right. Hadley Delta in the background rises approximately 4,000 metres (about 13,124 feet) above the plain. The base of the mountain is approximately 5 kilometers (about 3 statute miles) away. This photograph was taken by David R Scott, commander of the Apollo 15 mission. (Photo by The Print Collector/Print Collector/Getty Images)