Why does the Moon have bigger craters?
I got your name off the net. I was wondering if you might be able to help me with a question. Why are the largest craters we find on the Moon and Mercury so much larger then the ones found on the earth? (a.) because the earth’s magnetic fields protect us from impact (b.) because the largest craters were made early in each worlds history, and geological activity has erased all traces of this early period on the earth Is it “b”? Reply Magnetic fields are certainly no obstacle, while item (b) does have some validity. Certainly, much early cratering evidence has been erased–by weather and by the reworking of the surface by earthquakes, faulting etc. But you may also keep in mind some other factors: (1) Gravity is weaker on Mercury and the Moon, so ejecta from impacts that produce craters fly to greater distances. (2) Most of the Earth is covered by oceans, and because of plate tectonics, the ocean floor is constantly being reworked (see http://www.phy6.org/earthmag/reversal.htm and the bo
