[meteorite-list] Shielding of the Moon by earth

[Rob Matson]

Hi Melanie/List,

The side of the Moon that faces the Earth is only ~barely~ shielded
by the earth compared to the side facing away from Earth. In fact,
I would be surprised if the difference is even detectable as far as
cratering density. From the Moon's surface, the earth subtends
about 1.9 degrees, so a Full Earth looks over 14 times larger (in
"area") than does a Full Moon from earth. While that may seem large,
the amount of angular space shielded by the earth is tiny -- about
one part in 7000 for any portion of the lunar hemisphere with a
view of the earth. In other words, square mile for square mile,
if the earth had the Moon's vacuum, its surface would get hit just
as often as the Moon's.  --Rob