Effect of a giant impact on the thermal evolution of the moon

The effects of a giant impact on the thermal evolution of the Moon are investigated. It is found that an impact similar to that of Imbrium creates lateral temperature variations of more than 200 deg within the upper 200 km of the Moon. Starting with a common lithosphere of 70 km thickness, the lithosphere beneath the basin grows to 200 km in thickness within 0.5 b.y. after the impact, while that beneath the highlands reaches to only 100 km in thickness during this period. The model presented for the thermal evolution of the Moon is compatible with (1) the existence of mascons for more than 3 b.y., (2) the late magmatization and subsequent volcanic activities during 4 to 3 b.y. ago and (3) the negative gravity rings around the large mascons.