No, this is not a wheel of moldy Swiss cheese. It’s an illumination map of the South Pole of the Moon. There are some areas on the poles of the Moon, particularly the interior of craters that lie in permanent shadow while other areas remain sunlit for the majority of the year.
The Astronomical Research Center (A.R.C) mentioned that this image was taken by the Lunar Reconnaissance Orbiter Camera, which has a primary objective of unambiguously identifying these regions. This composite image contains over 1,700 images taken of the same area by the LROC Wide Angle Camera (WAC) over a six month period, which works out to six lunar days.
Here’s how the LROC team described how they created the image:
“Each image was map projected and converted to a binary image (if the ground was illuminated that pixel was set to one, and if shadowed zero) to differentiate between sunlit and shadowed regions.
All the binary images were then stacked, and then for each pixel it was determined what percentage of the time during six months that spot was illuminated. Presto – an illumination map! The LROC team is making daily (which is about 28 Earth days) and yearly illumination maps for both poles. Such maps will provide the foundation for planning future robotic and human missions to the poles.”