The third entry in my series of blog posts about Favorite Astro Plots contains one of the biggest discoveries from the Apollo program -- as well as one of the biggest questions in planetary science. The chart was nominated by planetary scientist Barbara Cohen. It has to do with the ages of surfaces on the Moon.
A few days ago, I wrote a post about the basins of the Moon -- a result of a trip down a rabbit hole of book research. Here's the next step in that journey: the Geologic Time Scales of Earth and the Moon.