Last week's intentional crash of a NASA probe on the far side of the moon added one more body to an already substantial graveyard of space hardware.
NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) slammed into the moon's surface, as planned, in the early hours of April 18, bringing an end to a $280 million mission that launched in September 2013.
LADEE's smash landing on the moon's far side is far from unique, said Philip Stooke of the University of Western Ontario in Canada, a space-mapping expert who documents lunar and planetary exploration. (The Greatest Moon Crashes of All Time)
"The total is six so far, and no landers. … Nothing has ever landed on the far side," Stooke said. Those six are all American, except for Okina, one of the little sub-satellites of the Japanese Kaguya mission that orbited the moon from September 2007 to June 2009.
"The first was Ranger 4 back in the mid-60s, when we were all a lot younger," Stooke said. "Then, three of the five Lunar Orbiters, and a sub-satellite released in lunar orbit by Apollo 16."
Stooke said that there could be others, since no one knows the crash sites of some hardware — for example, the Apollo 10 Lunar Module (LM) descent stage; the Apollo 11 and 16 LM ascent stages; the Apollo 15 sub-satellite; and the former Soviet Union's Luna 11, 12, 14, 19 and 22 missions. In addition, there's India's Chandrayaan 1 and another sub-satellite ejected during Japan's Kaguya mission.
"Several of them might be on the far side," Stooke said.
LADEE's final resting place is unclear at the moment, but NASA plans to look for the spot with its sharp-eyed Lunar Reconnaissance Orbiter probe (LRO).