Unveiling The Secrets Of The Midinfrared (3-5 Mu M) Moon

We know very well the Moon's appearance in the visible wavelengths. What the Moon in the midinfrared (MIR) looks like is still a mystery. We present detailed appearance of the MIR Moon observed by a high-resolution geostationary satellite and reveal the essence behind its appearance. The appearance of the MIR Moon is opposite to its normal visible appearance and shows limb darkening. Both the absolute and the relative brightness distribution of the MIR lunar disk changes with the solar incidence angle i. The signatures of the MIR Moon are controlled by both the reflection and the emission of the lunar surface. The center-to-limb temperature variation across the lunar disk is clearly shown. The slower decrease of the brightness temperature when moving away from the subsolar point than the Lambertian model represents topographic effects.Plain Language Summary The Moon's optical characteristics in visible and thermal infrared have long been observed with our eyes or with instruments. However, what the Moon looks like in the mid-infrared (MIR) is still a mystery. We show several amazing images of the MIR Moon taken by high-resolution geostationary satellite for different lunar phases. The entire lunar disk was imaged in high-resolution single exposure, which is advantageous for investigating the brightness distribution across the lunar disk compared to a mosaic of image frames from lunar-orbiting spacecrafts. The MIR Moon exhibits opposite trends to its normal visible appearance and shows limb darkening. Both the absolute and the relative brightness distribution of the MIR lunar disk evolve with the changing incidence of the solar illumination. The temperature variation across the lunar disk is also clearly shown.