Some surfaces have experienced more recent geological activity (like volcanism or erosion) that wiped out previously existing craters. They are referred to as "geologically younger" than surfaces that have not experienced activity. We can therefore use crater counts to determine the "age" of a surface, approximating how long ago the last geological event occurred in that area.

Using this technique (and assuming these pictures are representative of the crater density on the entire planet), rank the planets in order of their geological age, from oldest to youngest.