Cratering Rate

Current Cratering Rate

The above figure is for the cratering rate of the Moon. The cratering rate for the land masses on the Earth is roughly 10 times higher (can you think of reasons why?).

History of the Cratering Rate (and the Lunar Chronology)

Events:

Event                                 Billions of Years Ago

Lunar Formation                              4.6

   surface soft

   rate is unknown because of
   cratering saturation--craters
   overlap destroying evidence of
   earlier impacts

Crust Formation                              4.4

   Heavily cratered highlands regions
   are formed 

Start of Heavy Bombardment                   3.9

   Basin Formation 

   final heavy bombardment
    (final surge due to an unique
     event--debris from disruption 
     of an asteroid?)

Maria Formation (filling in of basins with
  lava flows                               
                                           3.9-3.2

Slow constant bombardment                    3.8

Today                                         0