@ Mike Richards
"They continued with radioisotope generators (RTGs) on missions to the Moon (to get round the 14 day Lunar nights) and outer planets; but it's worth remembering that two American RTGs been lost when coming back to Earth..."
The Moon is tidally locked to Earth, the same side is always pointing to Earth. Where you land if its day, it'll stay day, no 14 day nights...
Biting the hand that feeds IT
