Draw down the moon dating
I will climb back out of the rabbit hole eventually with lots of good stories about the geology of many different planets, but I'm going to have to tell those stories bit by bit.
It all begins, appropriately, with the history of impact basins on the Moon.
This map of lunar crustal thickness was derived from an analysis of GRAIL's gravity data.
The thickness varies from a high of 60 kilometers in the farside highlands to a low near zero within impact basins.
For a few basins, you can actually see one basin overlap another; that's noted in parentheses.
This is the framework for part of the origin story about the Moon, the second major chapter in the Moon's history, after its initial formation and cooling.
Basin names are in caps if they are in caps on the map above, to help you locate them.
It lists the basins from oldest to youngest, based on crater counting -- basins with more, bigger craters on top of them are older.
The trail that led me here has to do with geologic time scales -- the stories that geologists tell about the major events that happened in the history of a planet.This is all part of the work geologists are doing right now -- sorting out the order of events in the history of the moon and other solid-surfaced worlds in the solar system, trying to understand our origin story.Fascinating stuff, and I'll have more to say about this work in later posts.But when you have topographic data and gravity data, you can make maps that cause hidden basins to leap out at you, like they do in this map of lunar crustal thickness.Basins have thin crust (blue and green), and are often rimmed by thick crust (red and orange).