This unusual view of the Moon, made with the Green Bank Telescope (GBT), shows the glow from the Moon’s heat revealing features undetectable to an ordinary telescope that sees only reflected light. This image was made using a new, extremely sensitive radio camera called MUSTANG-2, which detects high frequency radio waves, and the GBT, the world’s largest fully steerable radio telescope. The wavelength of the radio waves detected by the camera is about 3.3mm (a frequency of 90 GHz), which makes it able to measure the temperature of the Moon as if it were sticking a thermometer into its surface.

In this thermal image, the Moon’s North Pole points toward the upper left, and the Sun’s illumination comes from the upper right. We can see the patterns of some of the vast dark plains, or maria, created by enormous lava flows billions of years ago. Ordinarily, when we look at the Moon in reflected sunlight, these maria give the Moon its distinctive pattern of dark patches, but in the MUSTANG-2/GBT image some appear bright, which means that they are warmer than their surroundings. One of these bright maria just to the upper right of center is the Sea of Tranquility, the landing…

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