Source: Journal of Geophysical Research: Planets
Like Janus, the Roman god of doorways, the Moon has two faces. Its near side, always facing the Earth, has a thin and, as some scientists have previously proposed, possibly hotter crust than the far side. Measuring the temperature or, more accurately, the heat flow of the Moon, is however difficult to do, especially if one wants to understand what the heat flow was like early in the history of our satellite, three to four billion years ago.
Ding and Zhu  show that a fundamental characteristic of large lunar basins can provide some constraint on ancient heat flow. The impact process forms an annulus of thickened crust around the basin proper. New simulations show that the annulus would relax and vanish over just 20 million years if the crust is hot enough. Large impact basins on the near side of the moon lack a crustal annulus, implying a thermal flow larger than 30 K/km and a high abundance of heat-producing elements in the crust. In contrast, similar basins on the far side have preserved their crustal annulus, implying a temperature gradient of less than 20 K/km. The presence or absence of a crustal annulus provides useful bounds on the temperature structure of the Moon at the time of basin formation.
Citation: Ding, M., & Zhu, M.-H. (2022). Effects of regional thermal state on the crustal annulus relaxation of lunar large impact basins. Journal of Geophysical Research: Planets, 127, e2021JE007132. https://doi.org/10.1029/2021JE007132
—Laurent G. J. Montési, Editor in Chief, Journal of Geophysical Research: Planets