This question struck me. I, too, googled it, and came up empty handed. I then asked on Quora, which at the time of this comment, has 5 not-unreasonable answers.

This question struck me. I, too, googled it, and came up empty handed. I then asked on Quora, which at the time of this comment, has 5 not-unreasonable answers. My favorite answer is Joshua Engel's: > It’s just a turn of phrase. He’s evoking the idea of “planet” as “one of the lights in the sky”, something people have long dreamed of. > It was an awkward phrase even at the time, though. George Low may have been a great administrator, but he’s a lousy writer. My red pen itched at every word. (In the very next sentence he misspells “mankind”.) He meant to be poetic, but his audience would have been confused by it, and that wouldn’t be the last time in that document. https://www.quora.com/Why-did-NASA-refer-to-the-Moon-as-a-planet-in-1970 https://www.quora.com/Why-did-NASA-refer-to-the-Moon-as-a-pl...