The Moon in the Microwave: Shedding New Light on the Lunar Farside

Abstract

AbstractA new lunar map was produced by subtracting the nocturnal microwave radiance data from two frequency channels with different penetrative potential. Chang’E−2 microwave radiometer (MRM) data show areas of anomalous high differences relating to both known and unknown young impact craters, most of which are located on the lunar farside. Thirty‐eight Features Of Interest (FOI) were selected and investigated by comparison with soil maturity maps (OMAT) and infrared‐derived data (H–Parameter), a parameter relating to thermal inertia. In some cases, the surface area of the microwave feature reaches distances of over 40 units of crater radii from the rim before abruptly dropping to background level within less than 10 km. The origin of such microwave variations remains unclear but is likely related to terrain roughness and fine ejecta materials which produce higher signal loss (“loss tangent”) at the uppermost surface layer. The observed discrepancy from the other datasets is due to the higher penetrative potential of microwave radiation, thus potentially carrying additional information on buried materials. The microwave‐derived FOIs appear to be transient within a geological timeframe and, in principle, a relationship between temperature differences at night in the two microwave channels, along with infrared data analysis, could be employed to derive a formation time of the crater. However, the low spatial resolution of the available microwave data precludes a reliable quantitative derivation at present.