Clear Skies

At 91% illumination, the Moon was in a waxing gibbous phase, a few days before full. The terminator — the line dividing the lit and unlit halves — lay close to the lunar limb, so most of the near side was sunlit while low-angle light still emphasized relief near the remaining shadowed margin. Gibbous phases commonly show the contrast between the dark basaltic maria, such as Mare Imbrium, Mare Serenitatis, Mare Tranquillitatis, and Oceanus Procellarum, and the brighter, older anorthositic highlands.

The Moon is Earth’s only natural satellite, with a mean distance of about 384,400 km and a diameter of 3,474 km. It is tidally locked, rotating once in the same 27.3-day period it takes to orbit Earth, so nearly the same hemisphere always faces us. Its surface records a long impact history: the heavily cratered highlands are mostly over 4 billion years old, while many maria formed when large impact basins were later flooded by basaltic lava. Surface temperatures vary widely, from roughly 120 °C in sunlight to below −170 °C during the lunar night.