Moon Crater Shapes
Date: 1999 - 2000
The craters on the moon are obviously round but
impacts with a grazing incidence should leave a V shaped crater. I would think that some percentage of the impacts would be at shallow angles of attack but this does not appear to be the case in photos.
Have they discovered such craters and if not why??
It doesn't work that way. A crater is like a frozen ripple, and
ripples are round. There is an asymmetric distribution of matter in
the ripple, and the blanket of stuff ejected from the surface, that do
record the angle of incidence. These are superimposed on the ripple,
but it's the ripple that is most noticeable because of its sharp
Actually, impacts at a grazing angle will also make a round hole. This was
a controversial point regarding Meteor Crater in Arizona, which was
basically the first site recognized on Earth as a meteor impact site. The
fact that no meteorite fragments were found in the earth below the center
of the crater was initially taken as evidence against the hypothesis that
the structure was an impact crater, but further research showed that if the
impact is very energetic, such as a rifle bullet fired into mud, the
resulting hole is round, even if the impact angle is quite flat.
Richard Barrans Jr., Ph.D.
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Update: June 2012