Passive Microwave Probing Mare Basalts in Mare Imbrium Using CE-2 CELMS Data

To evaluate the availability of the volcanism study, the microwave sounder (Chinese lunar exploration project, a microwave sounder, CELMS) data from Change'E -2 satellite were employed in this study to compare with the geologic results derived from optical data and radar data of Mare Imbrium, which is presented as the long duration and the last extensive phase of lunar volcanism. First, the normalized brightness temperature ( $T_{B}$ ) is generated to eliminate its strong latitude-dependent effect, which implies a good correlation with the titanium abundance. Moreover, difference between $T_{B}$ of the same frequency at noon and that at midnight ( ${\text{d}}T_{B}$ ) is deduced to evaluate the absorption features of the lunar regolith. According to the ${\text{d}}T_{B}$ change with frequency, a new geologic perspective is given to Mare Imbrium. The new interpretation map largely agrees with optical results in the regions with high (FeO + TiO2) abundance (FTA), and with the interpretation maps by radar data in the regions with low FTA. The statistical results validate the three-phase volcanism in Mare Imbrium. This study also hints the special importance of the CELMS data in understanding the basaltic volcanism of the Moon.